Road vehicles -- Specification of non-petroleum-based brake fluids for hydraulic systems

This document provides the specifications, requirements and test methods, for non-petroleum-based fluids used in road-vehicle hydraulic brake and clutch systems that are designed for use with such fluids and equipped with seals, cups or double-lipped type gland seals made of styrene-butadiene rubber (SBR) and ethylene-propylene elastomer (EPDM).

Véhicules routiers -- Spécifications pour liquides de frein à base non pétrolière pour systèmes hydrauliques

General Information

Status
Published
Publication Date
07-Jul-2020
Current Stage
9092 - International Standard to be revised
Start Date
24-Sep-2020
Ref Project

RELATIONS

Buy Standard

Standard
ISO 4925:2020 - Road vehicles -- Specification of non-petroleum-based brake fluids for hydraulic systems
English language
25 pages
sale 15% off
Preview
sale 15% off
Preview
Draft
ISO/PRF 4925 - Road vehicles -- Specification of non-petroleum-based brake fluids for hydraulic systems
English language
25 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

INTERNATIONAL ISO
STANDARD 4925
Third edition
2020-07
Road vehicles — Specification of non-
petroleum-based brake fluids for
hydraulic systems
Véhicules routiers — Spécifications pour liquides de frein à base non
pétrolière pour systèmes hydrauliques
Reference number
ISO 4925:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 4925:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 4925:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Materials ....................................................................................................................................................................................................................... 2

5 Specifications ........................................................................................................................................................................................................... 2

6 Test methods ............................................................................................................................................................................................................. 4

6.1 Viscosity ........................................................................................................................................................................................................ 4

6.1.1 General...................................................................................................................................................................................... 4

6.1.2 Repeatability (single analyst) ............................................................................................................................... 4

6.1.3 Reproducibility (multi-laboratory).................................................................................................................. 4

6.2 Equilibrium reflux boiling point (ERBP) .......................................................................................................................... 5

6.2.1 General...................................................................................................................................................................................... 5

6.2.2 Preparation of apparatus .......................................................................................................................................... 5

6.2.3 Test procedure ................................................................................................................................................................... 5

6.2.4 Repeatability (single analyst) ............................................................................................................................... 5

6.2.5 Reproducibility (multi-laboratory).................................................................................................................. 5

6.2.6 Wet ERBP test ..................................................................................................................................................................... 6

6.3 pH ....................................................................................................................................................................................................................... 9

6.4 Fluid stability ............................................................................................................................................................................................ 9

6.4.1 High-temperature stability ..................................................................................................................................... 9

6.4.2 Chemical stability .........................................................................................................................................................10

6.5 Corrosion ..................................................................................................................................................................................................10

6.5.1 Metal strip characteristics prior to testing .............................................................................................10

6.5.2 Preparation of joints ..................................................................................................................................................10

6.5.3 Test procedure ................................................................................................................................................................11

6.6 Fluidity and appearance at low temperatures ..........................................................................................................11

6.6.1 At −40 °C for 144 h ......................................................................................................................................................11

6.6.2 At −50 °C for 6 h.............................................................................................................................................................11

6.7 Water tolerance ...................................................................................................................................................................................12

6.7.1 At −40 °C for 22 h .........................................................................................................................................................12

6.7.2 At 60 °C for 22 h.............................................................................................................................................................12

6.8 Compatibility/miscibility with ISO 4926 fluid .........................................................................................................12

6.8.1 At −40 °C for 22 h .........................................................................................................................................................12

6.8.2 At 60 °C for 22 h.............................................................................................................................................................12

6.9 Resistance to oxidation .................................................................................................................................................................12

6.10 Effect on rubber ..................................................................................................................................................................................13

6.10.1 Test procedures..............................................................................................................................................................13

6.10.2 Repeatability (single analyst) ............................................................................................................................14

6.10.3 Reproducibility (multi-laboratory)...............................................................................................................14

6.11 Reserve alkalinity according to ASTM D 1121 ..........................................................................................................14

Annex A (normative) ISO styrene-butadiene rubber (SBR) brake cups for testing brake fluid ..........15

Annex B (normative) Corrosion test strips .................................................................................................................................................18

Annex C (informative) Corrosion strip assembly .................................................................................................................................19

Annex D (normative) Standard ethylene, propylene and diene (EPDM) terpolymer rubber

slabstock ....................................................................................................................................................................................................................20

Annex E (normative) Triethylene glycol monomethyl ether (TEGME) brake fluid grade ..........................22

Bibliography .............................................................................................................................................................................................................................25

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 4925:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee 33

Chassis systems and components.

This third edition cancels and replaces the second edition (ISO 4925:2005), which has been technically

revised.
The main changes compared to the previous edition are as follows:
— a terms and definitions clause was added (Clause 3);

— an additional class 7 is introduced and added to the already existing classes 3, 4, 5-1 and 6;

— the reserve alkalinity is added upon request out of the automotive industry;

— the intended introducing of a stroking test into a future revision of this document is replaced by the

intended introduction of a wear and noise test currently under development in the SAE and ISO TF

lubrication.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 4925:2020(E)
Introduction

The specifications for fluids given in this document incorporate a range of performance standards in

use throughout the world at the time of publication. To the already existing classes 3, 4, 5-1 and 6 an

additional class 7 is added.

The major use of these fluids is in the hydraulic brake and clutch systems of road vehicles, but they can

also be used in any suitable hydraulic system.
© ISO 2020 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 4925:2020(E)
Road vehicles — Specification of non-petroleum-based
brake fluids for hydraulic systems
1 Scope

This document provides the specifications, requirements and test methods, for non-petroleum-based

fluids used in road-vehicle hydraulic brake and clutch systems that are designed for use with such fluids

and equipped with seals, cups or double-lipped type gland seals made of styrene-butadiene rubber

(SBR) and ethylene-propylene elastomer (EPDM).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 37, Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties

ISO 48-2, Rubber, vulcanized or thermoplastic — Determination of hardness (hardness between 10 IRHD

and 100 IRHD)

ISO 812, Rubber, vulcanized or thermoplastic — Determination of low-temperature brittleness

ISO 815 (all parts), Rubber, vulcanized or thermoplastic — Determination of compression set

ISO 3104, Petroleum products — Transparent and opaque liquids — Determination of kinematic viscosity

and calculation of dynamic viscosity

ISO 4926, Road vehicle — Hydraulic braking systems — Non petroleum base reference fluids

ASTM D 91, Standard test method for precipitation number of lubricating oils
ASTM E 298, Standard test methods for assay of organic peroxides
ASTM D 395, Standard test methods for rubber property — Compression set

ASTM D 412, Standard test methods for vulcanized rubber and thermoplastic elastomers — Tension

ASTM D 746, Standard test method for brittleness temperature of plastics and elastomers by impact

ASTM D 865, Standard test method for rubber — Deterioration by heating in air (test tube enclosure)

ASTM D 1120, Standard test method for boiling point of engine coolants

ASTM D 1121, Standard test method for reserve alkalinity of engine coolants and antirusts

ASTM D 1123, Standard test methods for water in engine coolant concentrate by the Karl Fisher

reagent method
ASTM D 1415, Standard test method for rubber property — International hardness

ASTM D 3182, Standard practice for rubber — Materials, equipment and procedures for mixing standard

compounds and preparing standard vulcanized sheets

ASTM D 3185:2006, Standard test methods for rubber—Evaluation of SBR (Styrene-Butadiene Rubber)

including mixtures with oil
© ISO 2020 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 4925:2020(E)
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Materials

On visual inspection, the fluid shall be clear and free of suspended matter, dirt and sediment. The

quality of the materials used shall be such that the resulting product conforms to the requirements

of this document and that uniformity of performance is ensured. Fluids may be dyed, provided no

confusion is possible between them and other types of fluids.
5 Specifications

The product shall meet the requirements for the appropriate class in accordance with Table 1, using the

test methods according to Clause 6.
Table 1 — Brake fluid specifications — Tests and requirements
Requirement(s)
Test
method Test description Unit
Class Class Class Class Class
(subclause)
3 4 5–1 6 7
6.1 Viscosity
at −40 °C mm /s ≤1 500 ≤900 ≤750 ≤750
at 100 °C mm /s ≥1,5
6.2 Equilibrium reflux boiling point (ERBP) °C ≥205 ≥230 ≥260 ≥250 ≥260
6.2.6 Wet ERBP °C ≥140 ≥155 ≥180 ≥165 ≥180
6.3 pH — 7 to 11,5
6.4 Fluid stability
6.4.1 High-temperature stability °C ±5 °C
6.4.2 Chemical stability °C ±5 °C
6.5 Corrosion
Metal strip characteristics after testing
Mass change
Tinned iron mg/cm −0,2 to 0,2
Steel mg/cm −0,2 to 0,2
Aluminium mg/cm −0,1 to 0,1
Cast iron mg/cm −0,2 to 0,2
Brass mg/cm −0,4 to 0,4
Copper mg/cm −0,4 to 0,4
Aspect — No pitting or roughness outside
contact area
Staining/discoloration — Permitted
Liquid characteristics after testing

NOTE It is intended that a “wear” and “noise” lubrication test, currently under development in the SAE and ISO TF

lubrication, will be added to a future revision of this document.
NOTE Reserve alkalinity is requested by many customers.
2 © ISO 2020 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 4925:2020(E)
Table 1 (continued)
Requirement(s)
Test
method Test description Unit
Class Class Class Class Class
(subclause)
3 4 5–1 6 7
Aspect — No gel, none adhering crystals
pH — 7 to 11,5
Sediment % vol. ≤0,1
Rubber cup characteristics after testing
Blisters or carbon black separation — None
at surface
Hardness decrease IRHD ≤15
Base diameter increase mm ≤1,4
Volume increase % ≤16
6.6 Fluidity and appearance at low temperatures
6.6.1 at −40 °C for 144 h
Aspect — Clear and homogeneous
Bubble flow time s ≤10
Sediments — Absence
6.6.2 at −50 °C for 6 h
Aspect — Clear and homogeneous
Bubble flow time s ≤35
Sediments — Absence
6.7 Water tolerance
6.7.1 at −40 °C for 22 h
Aspect — Clear and homogeneous
Bubble flow time s ≤10
Sediments — Absence
6.7.2 at 60 °C for 22 h
Aspect — Clear and homogeneous
Sediments % vol. ≤0,05
6.8 Compatibility/miscibility with ISO 4926 fluid
6.8.1 at − 40 °C for 22 h
Aspect — Clear and homogeneous
Sediments — Absence
6.8.2 at 60 °C for 22 h
Aspect — Clear and homogeneous
Sediments % vol. ≤0,05
6.9 Resistance to oxidation
Metal strip aspect No pitting or roughness
no more than a trace of gum
Staining/discoloration — Permitted
Mass change of aluminium strip mg/cm −0,05 to +0,05
Mass change of cast iron strip mg/cm −0,3 to +0,3
6.10 Effect on rubber

NOTE It is intended that a “wear” and “noise” lubrication test, currently under development in the SAE and ISO TF

lubrication, will be added to a future revision of this document.
NOTE Reserve alkalinity is requested by many customers.
© ISO 2020 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 4925:2020(E)
Table 1 (continued)
Requirement(s)
Test
method Test description Unit
Class Class Class Class Class
(subclause)
3 4 5–1 6 7
6.10.1.1 Styrene butadiene rubber (SBR)
at 120 °C
Cup diameter increase mm 0,15 to 1,4
Hardness change IRHD −15 to 0
Volume increase % 1 to 16
Blisters or carbon black separation at None
surface
6.10.1.2 Ethylene propylene diene monomer (EPDM)
at 120 °C
Hardness change IRHD −15 to 0
Volume change % 0 to 10
Blisters or carbon black separation at None
surface
6.11 Reserve alkalinity according to ASTM D 1121 mL to be reported

NOTE It is intended that a “wear” and “noise” lubrication test, currently under development in the SAE and ISO TF

lubrication, will be added to a future revision of this document.
NOTE Reserve alkalinity is requested by many customers.
6 Test methods
6.1 Viscosity
6.1.1 General
Determine the kinematic viscosity of the fluid in accordance with ISO 3104.
2 2

Report the viscosity to the nearest 1 mm /s at −40 °C and to the nearest 0,01 mm /s at +100 °C.

Duplicate runs that agree within 1,2 % relative are acceptable for averaging (95 % confidence level).

6.1.2 Repeatability (single analyst)

The coefficient of variation of results (each the average of duplicates) obtained by the same analyst

on different days shall not be greater than 0,4 % at 47 degrees of freedom. Two such values shall be

considered unacceptable (95 % confidence level) if they differ by more than 1,2 %.

6.1.3 Reproducibility (multi-laboratory)

The coefficient of variation of results (each the average of duplicates) obtained by analysts in different

laboratories shall not be greater than 1,0 % at 15 degrees of freedom. Two such values shall be

considered unacceptable (95 % confidence level) if they differ by more than 3,0 %.

4 © ISO 2020 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 4925:2020(E)
6.2 Equilibrium reflux boiling point (ERBP)
6.2.1 General

Determine the ERBP of the fluid in accordance with ASTM D 1120 , but with the following changes to

the procedure and to the apparatus (see Figures 1 and 2).
— Thermometer: immersion shall be 76 mm and the thermometer shall be calibrated.

— Heat source: use either a suitable variac-controlled heating mantle designed to fit the flask, or an

electric heater with rheostat heat control.
6.2.2 Preparation of apparatus

Thoroughly clean and dry all glassware before use. Attach the flask to the condenser. When using a

heating mantle, place the mantle under the flask and support it with a suitable ring clamp and laboratory-

type stand, holding the whole assembly in place by a clamp. When using a rheostat-controlled heater,

centre a standard porcelain or other suitable refractory having a diameter opening of 32 mm to 38 mm

over the heating element of the electric heater and mount the flask on the refractory so that direct heat

is applied to the flask only through the opening in the refractory. Place the whole assembly in an area

free from draughts or other causes of sudden temperature changes.
6.2.3 Test procedure

Turn on the condenser water and apply heat to the flask at such a rate that the fluid is refluxing within

(10 ± 2) min at a rate higher than one drop per second. The reflux rate shall not exceed five drops per

second. Immediately adjust the heat input to obtain a specified equilibrium reflux rate of one drop

per second to two drops per second over the next (5 ± 2) min period. Maintain a timed and constant

equilibrium reflux rate of one drop per second to two drops per second for an additional 2 min; record the

average value of four temperature readings taken at 30 s intervals at the equilibrium reflux boiling point.

Report the boiling point to the nearest degree Celsius. Duplicate results that agree within 3 °C are

acceptable for averages (95 % confidence level).
6.2.4 Repeatability (single analyst)

The standard deviation of results (each the average of duplicates), obtained by the same analyst on

different days shall not be greater than 1,3 °C at 34 degrees of freedom. Two such values shall be

considered unacceptable (95 % confidence level) if they differ by more than 4 °C.

6.2.5 Reproducibility (multi-laboratory)

The standard deviation of results (each the average of duplicates), obtained by analysts in different

laboratories, shall be not greater than 3,5 °C at 15 degrees of freedom. Two such values shall be

considered unacceptable (95 % confidence level) if they differ by more than 10,5 °C.

1) Boiling chips for use with ASTM D 1120 can be obtained from Electro Minerals Co. (US) Inc, PO Box 423, Niagara

Falls, NY 14302, USA, or from the Society of Automotive Engineers (SAE), 400 Commonwealth Drive, Warrendale

Pa 15096, USA (RM-75). Boiling chip is an example of a suitable product available commercially. This information is

given for the convenience of users of this document and does not constitute an endorsement by ISO of this product.

© ISO 2020 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO 4925:2020(E)
6.2.6 Wet ERBP test
6.2.6.1 Apparatus

5.2.6.1.1 Two corrosion test jars or equivalent screw-top, straight-sided, round glass jars each having

a capacity of about 475 ml and approximate inner dimensions of 100 mm height by 75 mm diameter,

with matching lids having new, clean inserts providing water-proof and vapour-proof seals .

5.2.6.1.2 Desiccator and cover: bowl-form glass desiccator with 250 mm inside diameter, having a

matching tubulated cover fitted with a No. eight rubber stopper (see Figure 3).

5.2.6.1.3 Desiccator plate of 230 mm diameter, perforated porcelain desiccator plate, without feet,

glazed on one side (No.18 or equivalent) .

2) Suitable corrosion test jars (RM-49) and tinned steel lids (RM-63) can be obtained from the Society of Automotive

Engineers (SAE), 400 Commonwealth Drive, Warrendale, Pa 15096, USA.

3) Desiccator plates (No. 08-641C) can be obtained from Fischer Scientific, Springfield, New Jersey, USA or

CeramTec AG (No. 602786), Glaswerk Wertheim KG (No. 911743431) or equivalents, according to DIN/ISO 12911,

diameter 235 mm.
6 © ISO 2020 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 4925:2020(E)
Dimensions in millimetres
Key
1 water outlet
2 water jacket
3 thermometer
4 plastic screw cap or rubber sleeve
5 boiling chips
6 19/38 joint
7 water inlet
Figure 1 — Boiling point test apparatus
© ISO 2020 – All rights reserved 7
---------------------- Page: 12 ----------------------
ISO 4925:2020(E)
Dimensions in millimetres
Key
1 19/38 joint
2 fire-polished
3 screw joint or rubber sleeve
Internal diameter: 8 to 9.
Figure 2 — Detail of 100 ml short-neck flask
6.2.6.2 Test procedure

To determine the wet ERBP of the fluid in duplicate (see Figure 3), first, humidify a 350 ml sample of

the fluid under controlled conditions, using 350 ml of triethylene glycol mono methyl ether (TEGME),

follow Annex E, to establish the end point for humidification.
Lubricate the ground-glass joint of the desiccator.

Then, pour (450 ± 10) ml of distilled water into the desiccator and insert the perforated porcelain plate.

Immediately place one open corrosion test jar containing (350 ± 5) ml of the humidified test fluid into

the desiccator. Place a second open corrosion test jar containing (350 ± 5) ml of TEGME control fluid

into the same desiccator. The water content of the TEGME control fluid at the start of exposure shall be

(0,50 ± 0,05) % by weight.

Next, replace the desiccator cover and place immediately in a forced ventilation oven set at (50 ± 1) °C.

Periodically, during oven humidification, remove the rubber stopper from the desiccator and, using a

long-needle hypodermic syringe, quickly sample the control fluid and determine its water content in

accordance with ASTM D 1123. A maximum of 10 ml of fluid shall be removed in total. When the water

content of the control fluid has reached (3,70 ± 0,05) % by weight, remove the desiccator from the oven

and seal the test jar promptly using a screw-cap jar lid. Allow the sealed jar to cool for 60 min to 90 min

at (23 ± 5) °C. Determine the ERBP in accordance with 6.2.1 and 6.2.3.
8 © ISO 2020 – All rights reserved
---------------------- Page: 13 ----------------------
ISO 4925:2020(E)
Dimensions in millimetres
Key
1 rubber stopper
2 glass desiccator with tubulated cover
3 lubricated ground joint
4 TEGME (see Annex E)
5 corrosion test jars
6 fluid sample
7 porcelain desiccator plate
8 water
Figure 3 — Humidification apparatus
6.3 pH

Mix the fluid with an equal volume of a mixture 50 % ethanol and 50 % distilled water neutralized to

a pH of 7,0 ± 0,1. Determine the pH of the resulting solution electrometrically at (23 ± 5) °C, using a pH

meter equipped with a calibrated full range (0 to 14) glass electrode and a calomel reference electrode,

as specified in ASTM D 664.

Clouding or muddiness of the resulting solution is permitted in the determination.

6.4 Fluid stability
6.4.1 High-temperature stability

To determine the high-temperature stability of the fluid, heat a fresh sample of the original test fluid

to a temperature of (185 ± 2) °C according to the procedure specified in 6.2.3 and maintain it at that

temperature for (120 ± 5) min before determining the boiling point of the fluid, also in accordance with

© ISO 2020 – All rights reserved 9
---------------------- Page: 14 ----------------------
ISO 4925:2020(E)

6.2.3. The difference between this observed boiling point and that previously determined using that

test procedure shall be considered as the change in boiling point of the fluid.
6.4.2 Chemical stability
...

DRAFT INTERNATIONAL STANDARD
ISO/DIS 4925
ISO/TC 22/SC 33 Secretariat: DIN
Voting begins on: Voting terminates on:
2019-12-20 2020-03-13
Road vehicles — Specification of non-petroleum-base
brake fluids for hydraulic systems

Véhicules routiers — Spécifications pour liquides de frein à base non pétrolière pour systèmes hydrauliques

ICS: 75.120; 43.040.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
This document is circulated as received from the committee secretariat.
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 4925:2019(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO 2019
---------------------- Page: 1 ----------------------
ISO/DIS 4925:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/DIS 4925:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Materials ....................................................................................................................................................................................................................... 2

4 Specifications ........................................................................................................................................................................................................... 2

5 Test methods ............................................................................................................................................................................................................. 4

5.1 Viscosity ........................................................................................................................................................................................................ 4

5.1.1 General...................................................................................................................................................................................... 4

5.1.2 Repeatability (single analyst) ............................................................................................................................... 4

5.1.3 Reproducibility (multi-laboratory).................................................................................................................. 4

5.2 Equilibrium reflux boiling point (ERBP) .......................................................................................................................... 4

5.2.1 General...................................................................................................................................................................................... 4

5.2.2 Preparation of apparatus .......................................................................................................................................... 5

5.2.3 Test procedure ................................................................................................................................................................... 5

5.2.4 Repeatability (single analyst) ............................................................................................................................... 5

5.2.5 Reproducibility (multi-laboratory).................................................................................................................. 5

5.2.6 Wet ERBP test ..................................................................................................................................................................... 5

5.3 pH ....................................................................................................................................................................................................................... 8

5.4 Fluid stability ............................................................................................................................................................................................ 8

5.4.1 High-temperature stability ..................................................................................................................................... 8

5.4.2 Chemical stability ............................................................................................................................................................ 9

5.5 Corrosion ..................................................................................................................................................................................................... 9

5.5.1 Metal strip characteristics prior to testing ................................................................................................ 9

5.5.2 Preparation of joints ..................................................................................................................................................... 9

5.5.3 Test procedure ................................................................................................................................................................10

5.6 Fluidity and appearance at low temperatures ..........................................................................................................10

5.6.1 At − 40 °C for 144 h ........................................................................................................................................... ..........10

5.6.2 At − 50 °C for 6 h ...........................................................................................................................................................10

5.7 Water tolerance ...................................................................................................................................................................................11

5.7.1 At − 40 °C for 22 h ........................................................................................................................................................11

5.7.2 At 60 °C for 22 h.............................................................................................................................................................11

5.8 Compatibility/miscibility with ISO 4926 fluid .........................................................................................................11

5.8.1 At − 40 °C for 22 h ........................................................................................................................................................11

5.8.2 At 60 °C for 22 h.............................................................................................................................................................11

5.9 Resistance to oxidation .................................................................................................................................................................11

5.10 Effect on rubber ..................................................................................................................................................................................12

5.10.1 General...................................................................................................................................................................................12

5.10.2 Repeatability (single analyst) ............................................................................................................................13

5.10.3 Reproducibility (multi-laboratory)...............................................................................................................13

5.11 Reserve Alkalinity according to ASTM D 1121 .........................................................................................................13

Annex A (normative) ISO styrene-butadiene rubber (SBR) brake cups for testing brake fluid ..........14

Annex B (normative) Corrosion test strips .................................................................................................................................................17

Annex C (normative) Corrosion strip assembly .....................................................................................................................................18

Annex D (normative) Standard ethylene, propylene and diene (EPDM) terpolymer rubber

slabstock ....................................................................................................................................................................................................................19

Annex E (normative) Triethylene glycol monomethyl ether (TEGME) brake fluid grade ..........................21

Bibliography .............................................................................................................................................................................................................................24

© ISO 2019 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/DIS 4925:2019(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International

Standards adopted by the technical committees are circulated to the member bodies for voting.

Publication as an International Standard requires approval by at least 75 % of the member bodies

casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 4925 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee 33 “Chassis

systems and components”, WG 14 “Brake fluids”.

This third edition cancels and replaces the second edition (ISO 4925:2005), which has been technically

revised.
iv © ISO 2019 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/DIS 4925:2019(E)
Introduction

The specifications for fluids given in this International Standard incorporate a range of performance

standards in use throughout the world at the time of publication. The classes 3, 4, 5-1, 6 and 7 include

and partly exceed fluids technically equivalent to those designated DOT 3, DOT 4 and DOT 5.1.

The major use of these fluids is in the hydraulic brake and clutch systems of road vehicles, but they can

also be used in any suitable hydraulic system.
© ISO 2019 – All rights reserved v
---------------------- Page: 5 ----------------------
DRAFT INTERNATIONAL STANDARD ISO/DIS 4925:2019(E)
Road vehicles — Specification of non-petroleum-base
brake fluids for hydraulic systems
1 Scope

This International Standard gives the specifications — requirements and test methods — for

non-petroleum-base fluids used in road-vehicle hydraulic brake and clutch systems that are designed

for use with such fluids and equipped with seals, cups or double-lipped type gland seals made of

styrene-butadiene rubber (SBR) and ethylene-propylene elastomer (EPDM).
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO 37:1994, Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties

ISO 48:1994, Rubber, vulcanized or thermoplastic — Determination of hardness (hardness between

10 IRHD and 100 IRHD)
ISO 812:1991, Rubber, vulcanized — Determination of low-temperature brittleness

ISO 815:1991, Rubber, vulcanized or thermoplastic — Determination of compression set at ambient,

elevated or low temperatures

ISO 3104:1994, Petroleum products — Transparent and opaque liquids — Determination of kinematic

viscosity and calculation of dynamic viscosity

ISO 4926, Road vehicle — Hydraulic braking systems — Non petroleum base reference fluids

ASTM D 91, Standard test method for precipitation number of lubricating oils
ASTM E 298, Standard test methods for assay of organic peroxides
ASTM D 395, Standard test methods for rubber property — Compression set

ASTM D 412, Standard test methods for vulcanized rubber and thermoplastic elastomers — Tension

ASTM D 664, Standard test method for acid number of petroleum products by potentiometric titration

ASTM D 746, Standard test method for brittleness temperature of plastics and elastomers by impact

ASTM D 865, Test method for rubber — Deterioration by heating in air (test tube enclosure)

ASTM D 1120, Standard test method for boiling point of engine coolants

ASTM D 1121, Standard Test Method for Reserve Alkalinity of Engine Coolants and Antirusts

ASTM D 1123, Standard test method for water in engine coolant concentrate by the Fisher reagent method

ASTM D 1209, Standard test method for colour of clear liquids (platinum-cobalt scale)

ASTM D 1364, Standard test method for water in volatile solvents (Karl Fischer reagent titration method)

ASTM D 1415, Standard test method for rubber property — International hardness
© ISO 2019 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO/DIS 4925:2019(E)

ASTM D 1613, Standard test method for acidity in volatile solvents and chemical intermediates used in

paint, varnish, lacquer and related products

ASTM D 3182, Standard practice for rubber — Materials, equipment and procedures for mixing standard

compounds and preparing standard vulcanized sheets
SAE J 1703, Motor vehicle brake fluid
3 Materials

On visual inspection, the fluid shall be clear and free of suspended matter, dirt and sediment. The

quality of the materials used shall be such that the resulting product conforms to the requirements

of this International Standard and that uniformity of performance is ensured. Fluids may be dyed,

provided no confusion is possible between them and other types of fluids.
4 Specifications

The product shall meet the requirements for the appropriate class in accordance with Table 1, using the

test methods according to Clause 5.
Table 1 — Brake fluid specifications — Tests and requirements
Requirement(s)
Test meth-
od Test description Unit
Class Class Class Class Class7
(subclause)
3 4 5-1 6
5.1 Viscosity
at − 40 °C mm /s ≤ 1 500 ≤ 900 ≤ 750 ≤ 750
at 100 °C mm /s ≥ 1,5
5.2 Equilibrium reflux boiling point (ERBP) °C ≥ 205 ≥ 230 ≥ 260 ≥ 250 ≥ 260
5.2.6 Wet ERBP °C ≥ 140 ≥ 155 ≥ 180 ≥ 165 ≥ 180
5.3 pH — 7 to 11,5
5.4 Fluid stability
5.4.1 High-temperature stability °C ± 5 °C
5.4.2 Chemical stability °C ± 5 °C
5.5 Corrosion
Metal strip characteristics after testing
Mass change
Tinned iron mg/ − 0,2 to 0,2
Steel mg/ − 0,2 to 0,2
Aluminium mg/ − 0,1 to 0,1
Cast iron mg/ − 0,2 to 0,2
Brass mg/ − 0,4 to 0,4
Copper mg/ − 0,4 to 0,4
Aspect — No pitting or roughness outside
contact area
Staining/discoloration — Permitted
Liquid characteristics after testing
2 © ISO 2019 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/DIS 4925:2019(E)
Table 1 (continued)
Requirement(s)
Test meth-
od Test description Unit
Class Class Class Class Class7
(subclause)
3 4 5-1 6
Aspect — No gel, none adhering crystals
pH — 7 to 11,5
Sediment % vol. ≤ 0,1
Rubber cup characteristics after testing
Blisters or carbon black separation at surface — None
Hardness decrease IRHD ≤ 15
Base diameter increase mm ≤ 1,4
Volume increase % ≤ 16
5.6 Fluidity and appearance at low temperatures
5.6.1 at − 40 °C for 144 h
Aspect — Clear and homogeneous
Bubble flow time s ≤ 10
Sediments — Absence
5.6.2 at − 50 °C for 6 h
Aspect — Clear and homogeneous
Bubble flow time s ≤ 35
Sediments — Absence
5.7 Water tolerance
5.7.1 at − 40 °C for 22 h
Aspect — Clear and homogeneous
Bubble flow time s ≤ 10
Sediments — Absence
5.7.2 at 60 °C for 22 h
Aspect — Clear and homogeneous
Sediments % vol. ≤ 0,05
5.8 Compatibility/miscibility with ISO 4926 fluid
5.8.1 at − 40 °C for 22 h
Aspect — Clear and homogeneous
Sediments — Absence
5.8.2 at 60 °C for 22 h
Aspect — Clear and homogeneous
Sediments % vol. ≤ 0,05
5.9 Resistance to oxidation
Metal strip aspect No pitting or roughness
no more than a trace of gum
Staining/discoloration — Permitted
Mass change of aluminium strip mg/ − 0,05 to + 0,05
Mass change of cast iron strip mg/ − 0,3 to + 0,3
5.10 Effect on rubber
5.10.1.1 Styrene Butadiene Rubber (SBR)
at 120 °C
© ISO 2019 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO/DIS 4925:2019(E)
Table 1 (continued)
Requirement(s)
Test meth-
od Test description Unit
Class Class Class Class Class7
(subclause)
3 4 5-1 6
Cup diameter increase mm 0,15 to 1,4
Hardness change IRHD − 15 to 0
Volume increase % 1 to 16
Blisters or carbon black separation at surface — None
5.10.1.2 Ethylene Propylene Diene Monomer (EPDM)
at 120 °C
Hardness change IRHD − 15 to 0
Volume change % 0 to 10
Blisters or carbon black separation at surface — None
5.11 Reserve Alkalinity according to ASTM D 1121 mL to be reported

NOTE It is intended that a “wear” and “noise” lubrication test, currently under development in the SAE & ISO

TF lubrication, will be added to a future revision of this International Standard.

NOTE Reserve alkalinity is requested by many customers.
5 Test methods
5.1 Viscosity
5.1.1 General
Determine the kinematic viscosity of the fluid in accordance with ISO 3104.
2 2

Report the viscosity to the nearest 1 mm /s at − 40 °C and to the nearest 0,01 mm /s at + 100 °C.

Duplicate runs that agree within 1,2 % relative are acceptable for averaging (95 % confidence level).

5.1.2 Repeatability (single analyst)

The coefficient of variation of results (each the average of duplicates) obtained by the same analyst

on different days shall not be greater than 0,4 % at 47 degrees of freedom. Two such values shall be

considered unacceptable (95 % confidence level) if they differ by more than 1,2 %.

5.1.3 Reproducibility (multi-laboratory)

The coefficient of variation of results (each the average of duplicates) obtained by analysts in different

laboratories shall not be greater than 1,0 % at 15 degrees of freedom. Two such values shall be

considered unacceptable (95 % confidence level) if they differ by more than 3,0 %.

5.2 Equilibrium reflux boiling point (ERBP)
5.2.1 General

Determine the ERBP of the fluid in accordance with ASTM D 1120 , but with the following changes to

the procedure and to the apparatus (see Figures 1 and 2).
— Thermometer: immersion shall be 76 mm and the thermometer shall be calibrated.

1) Boiling chips for use with ASTM D 1120 can be obtained from Electro Minerals Co. (US) Inc, PO Box 423, Niagara

Falls, NY 14302, USA, or from the Society of Automotive Engineers (SAE), 400 Commonwealth Drive, Warrendale

Pa 15096, USA (RM-75).
4 © ISO 2019 – All rights reserved
---------------------- Page: 9 ----------------------
ISO/DIS 4925:2019(E)

— Heat source: use either a suitable variac-controlled heating mantle designed to fit the flask, or an

electric heater with rheostat heat control.
5.2.2 Preparation of apparatus

Thoroughly clean and dry all glassware before use. Attach the flask to the condenser. When using a

heating mantle, place the mantle under the flask and support it with a suitable ring clamp and laboratory-

type stand, holding the whole assembly in place by a clamp. When using a rheostat controlled heater,

centre a standard porcelain or other suitable refractory having a diameter opening of 32 mm to 38 mm

over the heating element of the electric heater and mount the flask on the refractory so that direct heat

is applied to the flask only through the opening in the refractory. Place the whole assembly in an area

free from draughts or other causes of sudden temperature changes.
5.2.3 Test procedure

Turn on the condenser water and apply heat to the flask at such a rate that the fluid is refluxing within

(10 ± 2) min at a rate higher than one drop per second. The reflux rate shall not exceed five drops per

second. Immediately adjust the heat input to obtain a specified equilibrium reflux rate of one drop

per second to two drops per second over the next (5 ± 2) min period. Maintain a timed and constant

equilibrium reflux rate of one drop per second to two drops per second for an additional 2 min; record the

average value of four temperature readings taken at 30 s intervals at the equilibrium reflux boiling point.

Report the boiling point to the nearest degree Celsius. Duplicate results that agree within 3 °C are

acceptable for averages (95 % confidence level).
5.2.4 Repeatability (single analyst)

The standard deviation of results (each the average of duplicates), obtained by the same analyst on

different days shall not be greater than 1,3 °C at 34 degrees of freedom. Two such values shall be

considered unacceptable (95 % confidence level) if they differ by more than 4 °C.

5.2.5 Reproducibility (multi-laboratory)

The standard deviation of results (each the average of duplicates), obtained by analysts in different

laboratories, shall be not greater than 3,5 °C at 15 degrees of freedom. Two such values shall be

considered unacceptable (95 % confidence level) if they differ by more than 10,5 °C.

5.2.6 Wet ERBP test
5.2.6.1 Apparatus

5.2.6.1.1 Two corrosion test jars or equivalent screw-top, straight-sided, round glass jars each having

a capacity of about 475 ml and approximate inner dimensions of 100 mm height by 75 mm diameter,

with matching lids having new, clean inserts providing water-proof and vapour-proof seals .

5.2.6.1.2 Desiccator and cover: bowl-form glass desiccator with 250 mm inside diameter, having a

matching tubulated cover fitted with a No. 8 rubber stopper (see Figure 3).

5.2.6.1.3 Desiccator plate of 230 mm diameter, perforated porcelain desiccator plate, without feet,

glazed on one side (No.18 or equivalent) .

2) Suitable corrosion test jars (RM-49) and tinned steel lids (RM-63) can be obtained from the Society of Automotive

Engineers (SAE), 400 Commonwealth Drive, Warrendale, Pa 15096, USA.

3) Desiccator plates (No. 08-641C) can be obtained from Fischer Scientific, Springfield, New Jersey, USA or

CeramTec AG (No. 602786), Glaswerk Wertheim KG (No. 911743431) or equivalents, according to DIN/ISO 12911,

diameter 235 mm.
© ISO 2019 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO/DIS 4925:2019(E)
Dimensions in millimetres
Key
1 water outlet
2 water jacket
3 thermometer
4 plastic screw cap or rubber sleeve
5 boiling chips
6 19/38 joint
7 water inlet
Figure 1 — Boiling point test apparatus
6 © ISO 2019 – All rights reserved
---------------------- Page: 11 ----------------------
ISO/DIS 4925:2019(E)
Dimensions in millimetres
Key
1 19/38 joint
2 fire-polished
3 screw joint or rubber sleeve
Internal diameter: 8 to 9.
Figure 2 — Detail of 100 ml short-neck flask
5.2.6.2 Test procedure

To determine the wet ERBP of the fluid in duplicate (see Figure 3), first, humidify a 350 ml sample of the

fluid under controlled conditions, using 350 ml of triethylene glycol mono methyl ether (TEGME), see

Annex E, to establish the end point for humidification.
Lubricate the ground-glass joint of the desiccator.

Then, pour (450 ± 10) ml of distilled water into the desiccator and insert the perforated porcelain plate.

Immediately place one open corrosion test jar containing (350 ± 5) ml of the humidified test fluid into

the desiccator. Place a second open corrosion test jar containing (350 ± 5) ml of TEGME control fluid

into the same desiccator. The water content of the TEGME control fluid at the start of exposure shall be

(0,50 ± 0,05) % by weight.

Next, replace the desiccator cover and place immediately in a forced ventilation oven set at (50 ± 1) °C.

Periodically, during oven humidification, remove the rubber stopper from the desiccator and, using a

long-needle hypodermic syringe, quickly sample the control fluid and determine its water content in

accordance with ASTM D 1123. A maximum of 10 ml of fluid only shall be removed in total. When the

water content of the control fluid has reached (3,70 ± 0,05) % by weight, remove the desiccator from

the oven and seal the test jar promptly using a screw-cap jar lid. Allow the sealed jar to cool for 60 min

to 90 min at (23 ± 5) °C. Determine the ERBP in accordance with clauses 5.2.1 and 5.2.3.

© ISO 2019 – All rights reserved 7
---------------------- Page: 12 ----------------------
ISO/DIS 4925:2019(E)
Dimensions in millimetres
Key
1 rubber stopper
2 glass desiccator with tubulated cover
3 lubricated ground joint
4 TEGME
5 corrosion test jars
6 fluid sample
7 porcelain desiccator plate
8 water
Figure 3 — Humidification apparatus
5.3 pH

Mix the fluid with an equal volume of a mixture 50% ethanol and 50% distilled water neutralized to a

pH of 7,0 ± 0,1. Determine the pH of the resulting solution electrometrically at (23 ± 5) °C, using a pH

meter equipped with a calibrated full range (0 to 14) glass electrode and a calomel reference electrode,

as specified in ASTM D 664.

Clouding or muddiness of the resulting solution is permitted in the determination.

5.4 Fluid stability
5.4.1 High-temperature stability

To determine the high-temperature stability of the fluid, heat a fresh sample of the original test fluid

to a temperature of (185 ± 2) °C according to the procedure specified in 5.2.3 and maintain at that

temperature for (120 ± 5) min before determining the boiling point of the fluid, also in accordance with

8 © ISO 2019 – All rights reserved
---------------------- Page: 13 ----------------------
ISO/DIS 4925:2019(E)

5.2.3. The difference between this observed boiling point and that previously determined using that

test procedure shall be considered as the change in boiling point of the fluid.
5.4.2 Chemical stability

To determine the chemical stability of the fluid, first, mix 30 ml of the fluid with 30 ml of the fluid

specified in ISO 4926. Determine the ERBP of this fluid mixture by use of the test apparatus specified

in 5.2, applying heat to the flask at such a rate that the fluid refluxes within (10 ± 2) min at a rate of

between one drop per second and five drops per second.

Record the maximum fluid temperature observed during the first minute after the fluid begins refluxing

at a rate higher than one drop per second. Over the next (15 ± 1) min, adjust and maintain the rate of

reflux to one drop per second to two drops per second. Maintain a timed and constant equilibrium

reflux rate of from one drop per second to two drops per second for an additional 2 min, recording

the average value of four temperature readings at 30 s intervals as the final equilibrium reflux boiling

point. Chemical reversion is evidenced by the change in temperature between the maximum fluid

temperature recorded and the final equilibrium reflux boiling point.
5.5 Corrosion
5.5.1 Metal strip characteristics prior to testing

Prepare two sets of strips from each of the metals listed in Table 1, each strip having a surface area

of (25
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.