SIST EN ISO 8504-2:2020

Preparation of steel substrates before application of paints and related products - Surface preparation methods - Part 2: Abrasive blast-cleaning (ISO 8504-2:2019)

This document specifies abrasive blast-cleaning methods for the preparation of steel surfaces before coating with paints and related products. It provides information on the effectiveness of the individual methods and their fields of application. It describes the equipment to use and the procedure to follow.

Vorbereitung von Stahloberflächen vor dem Auftragen von Beschichtungsstoffen - Verfahren für die Oberflächenvorbereitung - Teil 2: Strahlen (ISO 8504-2:2019)

Dieses Dokument legt Strahlverfahren für die Vorbereitung von Stahloberflächen vor dem Auftragen von Beschichtungsstoffen fest. Es enthält Angaben über die Wirksamkeit der einzelnen Verfahren und deren Anwendungsbereiche. Es beschreibt die zu verwendenden Werkzeuge und wie man sie benutzen muss.
ANMERKUNG Diese Verfahren sind hauptsächlich für warmgewalzten Stahl zum Entfernen von Zunder, Rost usw. vorgesehen. Sie können aber auch auf kaltgewalzten Stahl angewendet werden, wenn dieser so dick ist, dass er durch die Einwirkung des Strahlmittels nicht verformt wird.

Préparation des subjectiles d'acier avant application de peintures et de produits assimilés - Méthodes de préparation des subjectiles - Partie 2: Décapage par projection d'abrasif (ISO 8504-2:2019)

Le présent document spécifie des méthodes de décapage par projection d'abrasif pour la préparation des subjectiles d'acier avant application de peintures et de produits assimilés. Il fournit des informations sur l'efficacité des différentes méthodes et leurs domaines d'application. Il décrit l'appareillage à utiliser et le mode opératoire à suivre.
NOTE       Ces méthodes sont essentiellement destinées aux aciers laminés à chaud, pour éliminer la calamine, la rouille, etc., mais elles peuvent s'appliquer également aux aciers laminés à froid présentant une épaisseur suffisante pour supporter sans déformation l'impact du jet d'abrasif.

Priprava jeklenih podlag pred nanašanjem barv in sorodnih premazov - Postopki priprave površine - 2. del: Peskanje z abrazivi (ISO 8504-2:2019)

Ta dokument določa postopke peskanja z abrazivi za pripravo jeklenih površin pred nanašanjem barv in sorodnih premazov. Zagotavlja informacije o učinkovitostih posameznih metod in njihovih področjih uporabe. Opisuje opremo, ki jo je treba uporabiti, in postopke, ki jih je treba upoštevati.

General Information

• Status: Published
• Public Enquiry End Date: 04-Mar-2019
• Publication Date: 11-Dec-2019
• ICS: 25.220.10 - Surface preparation
• ICS: 87.020 - Paint coating processes
• Technical Committee: IBLP - Paints and varnishes
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 04-Dec-2019
• Due Date: 08-Feb-2020
• Completion Date: 12-Dec-2019
• Ref Project: EN ISO 8504-2:2019 - Preparation of steel substrates before application of paints and related products - Surface preparation methods - Part 2: Abrasive blast-cleaning (ISO 8504-2:2019)

Relations

• Replaces: SIST EN ISO 8504-2:2002 - Preparation of steel substrates before application of paints and related products - Surface preparation methods - Part 2: Abrasive blast-cleaning (ISO 8504-2:2000)
• Effective Date: 01-Jan-2020
• Replaces: SIST EN ISO 8504-2:2002 - Preparation of steel substrates before application of paints and related products - Surface preparation methods - Part 2: Abrasive blast-cleaning (ISO 8504-2:2000)
• Effective Date: 08-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 8504-2:2020
01-januar-2020
Nadomešča:
SIST EN ISO 8504-2:2002
Priprava jeklenih podlag pred nanašanjem barv in sorodnih premazov - Postopki
priprave površine - 2. del: Peskanje z abrazivi (ISO 8504-2:2019)

Preparation of steel substrates before application of paints and related products -

Surface preparation methods - Part 2: Abrasive blast-cleaning (ISO 8504-2:2019)
Vorbereitung von Stahloberflächen vor dem Auftragen von Beschichtungsstoffen -
Verfahren für die Oberflächenvorbereitung - Teil 2: Strahlen (ISO 8504-2:2019)

Préparation des subjectiles d'acier avant application de peintures et de produits

assimilés - Méthodes de préparation des subjectiles - Partie 2: Décapage par projection

d'abrasif (ISO 8504-2:2019)
Ta slovenski standard je istoveten z: EN ISO 8504-2:2019
ICS:
25.220.10 Priprava površine Surface preparation
87.020 Postopki za nanašanje Paint coating processes
barvnih premazov
SIST EN ISO 8504-2:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 8504-2:2020
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SIST EN ISO 8504-2:2020
EN ISO 8504-2
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2019
EUROPÄISCHE NORM
ICS 25.220.10 Supersedes EN ISO 8504-2:2001
English Version
Preparation of steel substrates before application of paints
and related products - Surface preparation methods - Part
2: Abrasive blast-cleaning (ISO 8504-2:2019)

Préparation des subjectiles d'acier avant application de Vorbereitung von Stahloberflächen vor dem Auftragen

peintures et de produits assimilés - Méthodes de von Beschichtungsstoffen - Verfahren für die

préparation des subjectiles - Partie 2: Décapage par Oberflächenvorbereitung - Teil 2: Strahlen (ISO 8504-

projection d'abrasif (ISO 8504-2:2019) 2:2019)
This European Standard was approved by CEN on 30 September 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 8504-2:2019 E

worldwide for CEN national Members.
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SIST EN ISO 8504-2:2020
EN ISO 8504-2:2019 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 8504-2:2020
EN ISO 8504-2:2019 (E)
European foreword

This document (EN ISO 8504-2:2019) has been prepared by Technical Committee ISO/TC 35 "Paints

and varnishes" in collaboration with Technical Committee CEN/TC 139 “Paints and varnishes” the

secretariat of which is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by May 2020, and conflicting national standards shall be

withdrawn at the latest by May 2020.

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

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

This document supersedes EN ISO 8504-2:2001.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 8504-2:2019 has been approved by CEN as EN ISO 8504-2:2019 without any

modification.
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SIST EN ISO 8504-2:2020
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SIST EN ISO 8504-2:2020
INTERNATIONAL ISO
STANDARD 8504-2
Third edition
2019-10
Preparation of steel substrates before
application of paints and related
products — Surface preparation
methods —
Part 2:
Abrasive blast-cleaning
Préparation des subjectiles d'acier avant application de peintures et
de produits assimilés — Méthodes de préparation des subjectiles —
Partie 2: Décapage par projection d'abrasif
Reference number
ISO 8504-2:2019(E)
ISO 2019
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SIST EN ISO 8504-2:2020
ISO 8504-2:2019(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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
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SIST EN ISO 8504-2:2020
ISO 8504-2:2019(E)
Contents Page

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

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

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

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

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Abrasives ....................................................................................................................................................................................................................... 2

4.1 Materials and types ............................................................................................................................................................................. 2

4.2 General requirements ....................................................................................................................................................................... 4

4.2.1 Technical ................................................................................................................................................................................. 4

4.2.2 Health and safety ............................................................................................................................................................. 4

4.3 Selection considerations ................................................................................................................................................................. 4

5 Abrasive blast-cleaning methods ........................................................................................................................................................ 5

5.1 Dry abrasive blast-cleaning .......................................................................................................................................................... 5

5.1.1 Centrifugal abrasive blast-cleaning ................................................................................................................. 5

5.1.2 Compressed-air abrasive blast-cleaning ..................................................................................................... 6

5.1.3 Vacuum or suction-head abrasive blast-cleaning ................................................................................ 6

5.2 Wet abrasive blast-cleaning ......................................................................................................................................................... 7

5.2.1 General...................................................................................................................................................................................... 7

5.2.2 Moisture-injection abrasive blast-cleaning (compressed-air moisture-

injection abrasive blast- cleaning) .................................................................................................................... 7

5.2.3 Compressed-air wet abrasive blast-cleaning .......................................................................................... 8

5.2.4 Slurry blast-cleaning .................................................................................................................................................... 8

5.2.5 Pressurized-liquid blast-cleaning ..................................................................................................................... 9

6 Procedure..................................................................................................................................................................................................................... 9

6.1 Preparation before blast-cleaning .......................................................................................................................................... 9

6.2 Blast-cleaning ........................................................................................................................................................................................... 9

6.3 After blast-cleaning ..........................................................................................................................................................................10

7 Assessment of the blast-cleaned surface..................................................................................................................................10

Bibliography .............................................................................................................................................................................................................................11

© ISO 2019 – All rights reserved iii
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SIST EN ISO 8504-2:2020
ISO 8504-2:2019(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.

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 35, Paints and varnishes, Subcommittee

SC 12, Preparation of steel substrates before application of paints and related products.

This third edition cancels and replaces the second edition (ISO 8504-2:2000), which has been technically

revised. The main changes compared to the previous edition are as follows:
— update of Clause 2, normative references;
— editorial revision.
A list of all parts in the ISO 8504 series can be found on the ISO website.

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 2019 – All rights reserved
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SIST EN ISO 8504-2:2020
ISO 8504-2:2019(E)
Introduction

The performance of protective coatings of paint and related products applied to steel is significantly

affected by the state of the steel surface immediately prior to painting. The principal factors that are

known to influence this performance are
— the presence of rust and mill scale,

— the presence of surface contaminants, including salts, dust, oils and greases, and

— the surface profile.

The ISO 8501 series, the ISO 8502 series and the ISO 8503 series provide methods for assessing these

factors, while the ISO 8504 series provides requirements and guidance on the preparation methods

that are available for cleaning steel substrates, indicating the capabilities of each in attaining specified

levels of cleanliness.

The ISO 8504 series is applicable to new and corroded steel surfaces and to steel surfaces that are

uncoated or have been previously coated with paints and related products.

These International Standards do not contain provisions for the protective coating system to be applied

to the steel surface. They do not contain provisions for the surface quality requirements for specific

situations even though surface quality can have a direct influence on the choice of protective coating

to be applied and on its performance. Such provisions are found in other documents such as national

standards and codes of practice. Users of these International Standards should ensure the qualities

specified are

— compatible and appropriate both for the environmental conditions to which the steel will be exposed

and for the protective coating system to be used, and
— within the capability of the cleaning procedure specified.

The primary objective of surface preparation is to ensure the removal of deleterious matter and to

obtain a surface that permits satisfactory adhesion of the priming paint to steel. It is also intended to

assist in reducing the amounts of contaminants that initiate corrosion.

Abrasive blast-cleaning is a most effective method for mechanical surface preparation. It is widely

applicable because this method of surface preparation has a number of versatile features listed below.

— The method allows a high production rate.

— The equipment can be stationary or mobile and is adaptable to the objects to be cleaned.

— The method is applicable to most types and forms of steel surface.

— Many different surface states can be produced, for example different preparation grades and surface

profiles.

— Effects such as cleaning, peening, roughening, levelling and lapping can be produced.

— It is possible to remove selectively partly failed coatings, leaving sound coatings intact.

— Abrasive ricochet (rebound) enables the cleaning of otherwise inaccessible areas.

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SIST EN ISO 8504-2:2020
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SIST EN ISO 8504-2:2020
INTERNATIONAL STANDARD ISO 8504-2:2019(E)
Preparation of steel substrates before application of paints
and related products — Surface preparation methods —
Part 2:
Abrasive blast-cleaning
1 Scope

This document specifies abrasive blast-cleaning methods for the preparation of steel surfaces before

coating with paints and related products. It provides information on the effectiveness of the individual

methods and their fields of application. It describes the equipment to use and the procedure to follow.

NOTE These methods are essentially intended for hot-rolled steel to remove mill scale, rust, etc. but could

also be used for cold-rolled steel of sufficient thickness to withstand the deformation caused by the impact of

abrasive.
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 4628-3, Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity and

size of defects, and of intensity of uniform changes in appearance — Part 3: Assessment of degree of rusting

ISO 8501 (all parts), Preparation of steel substrates before application of paints and related products —

Visual assessment of surface cleanliness

ISO 8502 (all parts), Preparation of steel substrates before application of paints and related products —

Tests for the assessment of surface cleanliness

ISO 8503 (all parts), Preparation of steel substrates before application of paints and related products —

Surface roughness characteristics of blast-cleaned steel substrates

ISO 11124 (all parts), Preparation of steel substrates before application of paints and related products —

Specifications for metallic blast-cleaning abrasives

ISO 11126 (all parts), Preparation of steel substrates before application of paints and related products —

Specifications for non-metallic blast-cleaning abrasives
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

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/
3.1
abrasive blast-cleaning

impingement of a high-kinetic-energy stream of abrasive onto the surface to be prepared

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SIST EN ISO 8504-2:2020
ISO 8504-2:2019(E)
3.2
blast-cleaning abrasive
solid material intended to be used for abrasive blast-cleaning (3.1)
3.3
shot

particle that is predominantly round, that has a length of less than twice the maximum particle width

and that does not have edges, broken faces or other sharp surface defects
3.4
grit

particle that is predominantly angular, that has fractured faces and sharp edges and that is less than

half-round in shape
3.5
cylindrical

particle that is sharp-edged, that has a diameter-to-length ratio of 1:1 and that is cut so that its faces are

approximately at right angles to their centreline
4 Abrasives
4.1 Materials and types

4.1.1 A wide variety of natural and synthetic solid materials are used for abrasive blast-cleaning. Solid

materials commonly in use for the preparation of steel surfaces before coating are given in Table 1. Each

material provides a characteristic performance and surface finish.

When selecting a blast-cleaning abrasive, the following factors relating to its initial condition shall be

taken into account:
— sub-group and type (see Table 1);
— indication of chemical composition;
— range of particle size (see 4.1.2);

— particle hardness (for example Vickers, Rockwell or Mohs, or as measured by another appropriate

method).

NOTE The ISO 11124 series, the ISO 11125 series, the ISO 11126 series and the ISO 11127 series are

International Standards on metallic and non-metallic blast-cleaning abrasives.
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SIST EN ISO 8504-2:2020
ISO 8504-2:2019(E)

4.1.2 The size and shape of the particles of an abrasive might change during use or re-use and this

change can affect the resultant surface texture of the blast-cleaned steel.
Table 1 — Commonly used blast-cleaning abrasives for steel substrate preparation
Type Abbreviation Initial Comparator Remarks
particle
shape
(see
Table 2)
Metallic (M) Cast iron Chilled M/CI G G Mainly
blast-cleaning for com-
abrasives pressed-air
blast-clean-
ing
Cast steel High-carbon M/HCS S or G S or G Mainly for
centrifugal
Low-carbon M/LCS S S
blast-clean-
Cut steel — M/CW C S
ing
wire
Non-me- Natural Olivine N/OL G G Mainly
tallic (N) for com-
Staurolite N/ST S G
blast-cleaning pressed-air
c Almandite garnet N/GA G G
abrasives blast-clean-
ing
Synthetic Iron slag (Calcium N/FE1 G G Mainly
silicate) for com-
pressed-air
Steel slag (Calcium N/FE2 G/S
blast-clean-
silicate)
ing
Copper re- (Iron N/CU G/S
finery slag silicate)
Nickel slag (Iron silicate) N/NI1 G
Ferronickel (Magnesium N/NI2 G/S
slag silicate)
Coal fur- (Aluminium N/CS G
nace slag silicate)
Fused aluminium oxide N/FA G G —
Key
M: Metallic blast-cleaning abrasives
N: Non-metallic blast-cleaning abrasives

Comparator to be used when assessing the resultant surface profile. The method for evaluating the surface

profile by comparator is described in ISO 8503-2.

Certain types of abrasive rapidly change their shape when used, depending on hardness. As soon as this hap-

pens, the appearance of the surface profile changes and becomes closer to that of the "shot" comparator.

International Standards for the range of abrasives given here are the ISO 11124 series for metallic

blast-cleaning abrasives, and the ISO 11126 series for non-metallic blast-cleaning abrasives.

Table 2 — Initial particle shape
Designation and initial particle shape Abbreviation
Shot — round S
Grit — angular, irregular G
Cylindrical — sharp-edged C
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SIST EN ISO 8504-2:2020
ISO 8504-2:2019(E)
4.2 General requirements
4.2.1 Technical

Abrasives shall be dry (except when added to pressurized liquid or slurry blast-cleaning systems) and

shall be free-flowing to permit consistent metering into the blast stream.

Abrasives shall meet the requirements specified in the ISO 11124 series and in the ISO 11126 series

and shall be free from corrosive constituents and adhesion-impairing contaminants. Because of their

deleterious effect on the blast-cleaned steel surface, permanently contaminated abrasives (for example

those that cannot be cleaned before recycling and those produced from slag that has been granulated

by the use of saline water, i.e. sea water, for cooling) are not permitted.

The abrasive is typically propelled either by centrifugal force or by a high-velocity stream of fluid such

as air or water to remove rust, mill scale, existing coatings and other contaminants and expose the

substrate. The cleaned surface has a characteristic secondary profile dependent on the blast-cleaning

conditions, the properties of the abrasive, the initial condition of the surface and the properties of

the steel being blast-cleaned. The initial surface roughness or primary profile can be altered by the

abrasive blast-cleaning procedure. Surface profiles are assessed using the method described in

ISO 8503-2. When selecting a surface preparation method, it is necessary to consider the preparation

grade required to give a level of surface cleanliness and, if required, a surface profile (roughness), such

as coarse, medium or fine (see ISO 8503-1 and ISO 8503-2), appropriate to the coating system to be

applied to the steel surface. Since the cost of surface preparation is usually in proportion to the level

of cleanliness, a preparation grade appropriate to the purpose and type of coating system or a coating

system appropriate to the preparation grade which can be achieved should be chosen.

4.2.2 Health and safety

The procedures described in this document shall be carried out by suitably trained and/or supervised

personnel. The substances and procedures used in these methods can be injurious to health if adequate

precautions are not taken. Attention is drawn in the text to certain specific hazards. This document

refers only to the technical suitability of the methods and does not absolve the user from statutory

obligations relating to health and safety.

WARNING — Equipment, materials and abrasives used for surface preparation can be hazardous.

It is important to ensure that adequate instructions are given and that all required precautions

are exercised.
4.3 Selection considerations

4.3.1 Selection of a suitable abrasive, together with an appropriate blast-cleaning method and

operating conditions, is necessary to achieve the required standard of surface preparation.

The type of blast-cleaning abrasive — i.e. its particle size distribution, shape, hardness, density and

impact behaviour (deformation or shatter characteristics) — is important in determining the standards

of cleanliness, the cleaning rate and the resulting surface profile of the blast-cleaned surface.

The particle size distribution of abrasives should be determined using the methods specified in

ISO 11125-2 and ISO 11127-2 respectively.

4.3.2 Preliminary blast-cleaning tests are recommended to determine the most effective abrasive, the

resulting surface preparation grade and the resulting surface profile (see ISO 8501-1 or ISO 8501-2 and

ISO 8503-2). If recycled abrasive is used for the surface preparation work, a preliminary test should be

carried out with the same material, as new abrasive might give misleading results [see also 4.3.3 c)].

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ISO 8504-2:2019(E)

4.3.3 When selecting an abrasive, the following considerations should be taken into account:

a) The influence of a particular particle size on the resulting surface profile is different for metallic

abrasives and for non-metallic abrasives. This is because the shatter characteristics differ and

because differences in density affect the kinetic energy of the abrasive particles.

b) A balanced mixture of particle sizes will produce the optimum level of cleanliness, cleaning rate

and surface profile.
c) In blast-cleaning plants where the abrasive is recycled, it is necessary
— to remove dust and contaminants before the abrasive is re-used, and

— to make up for the abrasive which is lost by wear and adherence to the workpieces. This is done

by controlled addition of new abrasive so that the abrasive mixture is maintained within the

prescribed particle size limits or particle size distribution.

Complete renewal of abrasive charges in recycling machines requires a period of use before the mixture

reaches a steady condition.
5 Abrasive blast-cleaning methods
5.1 Dry abrasive blast-cleaning
5.1.1 Centrifugal abrasive blast-cleaning
5.1.1.1 Principle

Centrifugal abrasive blast-cleaning is carried out on fixed installations or mobile units in which the

abrasive is fed to rotating wheels or impellers positioned to throw the abrasive evenly and at high

velocity on to the surface to be cleaned.
5.1.1.2 Field of application

The method is suitable for continuous operation on workpieces with accessible surfaces. It is also

applicable to workpieces having different rust grades (see ISO 8501-1).

NOTE Most centrifugal abrasive blast-cleaning equipment is stationary and the abrasive is circulated in

a closed system. The workpieces are either fed through or rotated within the equipment. In certain cases, the

equipment might be mobile, a
...