oSIST prEN ISO 9455-8:2026

• Abstract:

  Describes the principle, the reagents and materials, the apparatus, the test procedure, the calculation of results, the precision and the contents of the test report.

• Status: Not Published
• Public Enquiry End Date: 01-Dec-2026
• ICS: 25.160.50 - Brazing and soldering
• Technical Committee: VAR - Welding
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 10-Sep-2026
• Due Date: 28-Jan-2027
• Ref Project: prEN ISO 9455-8 - Soft soldering fluxes - Test methods - Part 8: Determination of zinc content (ISO/FDIS 9455-8:2026)

• Revises: SIST EN 29455-8:1998 - Soft soldering fluxes - Test methods - Part 8: Determination of zinc content (ISO 9455-8:1991)
• Effective Date: 01-Nov-2026

oSIST prEN ISO 9455-8:2026 is a Slovenian standard published by SIST and identical to prEN ISO 9455-8. It specifies a laboratory method for determining the zinc content of soft soldering fluxes, using EDTA titration on water soluble fluxes of type 3. It is written for laboratories, manufacturers, quality managers and buyers who need a repeatable zinc-content check on flux samples.

What does oSIST prEN ISO 9455-8:2026 specify?

oSIST prEN ISO 9455-8:2026 specifies the principle, reagents and materials, apparatus, procedure, calculation of results, precision and test report for zinc determination in soft soldering fluxes. The method applies to an aqueous solution of flux with about 25 % zinc, expressed as zinc chloride, and says that solid fluxes or substantially different concentrations require the sample amount to be adjusted.

The document is organized into these main clauses:

• Clause 1 - Scope
• Clause 2 - Normative references
• Clause 3 - Terms and definitions
• Clause 4 - Principle
• Clause 5 - Reagents
• Clause 6 - Apparatus
• Clause 7 - Procedure
• Clause 8 - Calculation of results
• Clause 9 - Precision
• Clause 10 - Test report

A bibliography follows the main clauses and cites ISO 9454-1.

What are the key requirements of oSIST prEN ISO 9455-8:2026?

oSIST prEN ISO 9455-8:2026 is a titrimetric method, so the important points are how the sample is prepared, how interferences are handled, and how the endpoint is read. Those details matter because the result depends on pH control, sample size, and correct reading of the colour change.

• Clause 4 - Principle: the flux solution is treated with sulfuric acid, ammonium chloride and ammonia, any precipitated iron is removed as hydroxide, and the zinc is measured by titration with EDTA. In practice, this means the analyst must remove iron interference before titrating.
• Clause 5 - Reagents: only recognized analytical quality reagents and distilled or deionized water are used, and the document specifies the EDTA solution, buffer solution, sulfuric acid, Eriochrome black T mixture, hydrochloric acid, ascorbic acid, ammonium chloride and ammonia solution. This matters because reagent quality affects the endpoint and the result.
• Clause 6 - Apparatus: ordinary laboratory apparatus is sufficient. That keeps the method practical for routine quality-control labs.
• Clause 7 - Procedure: the test is carried out in triplicate, starting with 25.0 ml of sample, then dilution, alkalinization, indicator addition and titration to a blue endpoint. If the flux concentration differs appreciably from the stated level, the sample volume is adjusted.
• Clause 7 - Sample handling: solid fluxes are dissolved in water so that the test sample has a zinc content around 25 %. This means the method is aimed at prepared solutions, not untreated solids.
• Clause 8 - Calculation: the zinc content of the original flux sample is calculated as zinc chloride from the EDTA volume and the sample density at 20 °C, determined with a hydrometer. If the sample was solid or a different sample volume was used, the calculation has to be adjusted.
• Clause 9 - Precision: the precision statement is based on tests on three fluxes covering 17 % (m/m) to 28 % (m/m) zinc, with four laboratories taking part. The reported precision data help users judge how much variation to expect between repeated tests and between laboratories.
• Clause 10 - Test report: the report records the sample identification, the reference to ISO 9455-8, the results, any unusual features and any operation that was optional or outside the document. This is important for traceability and comparison of results.

What terms does oSIST prEN ISO 9455-8:2026 define?

oSIST prEN ISO 9455-8:2026 does not provide a separate terms-and-definitions set, but it uses a few key terms and abbreviations that matter in practice.

• Type 3 - The water soluble flux category covered by the method, as defined in ISO 9454-1.
• EDTA - Disodium dihydrogen ethylenediaminetetra-acetate, the standard titrant used to measure zinc by complexation.
• Eriochrome black T - The indicator mixture used to show the titration endpoint by a colour change to blue.
• pH 10 buffer - The ammonium chloride and ammonia mixture used to hold the solution at the alkaline pH needed for the titration.
• Repeatability - The expected closeness of results when the same laboratory repeats the test under similar conditions.
• Reproducibility - The expected closeness of results when different laboratories perform the test.

Who uses oSIST prEN ISO 9455-8:2026?

oSIST prEN ISO 9455-8:2026 is used by laboratories that test soft soldering fluxes, by flux manufacturers, and by quality teams that need to verify zinc content. It is also relevant to buyers and specifiers who need a documented test method for incoming inspection, product release or contract checking in the soldering and brazing materials field.

What changed in oSIST prEN ISO 9455-8:2026 from the previous edition?

oSIST prEN ISO 9455-8:2026 replaces ISO 9455-8:1991. The foreword says this second edition is a minor revision and that the normative references were updated.

Which standards are used with oSIST prEN ISO 9455-8:2026?

The document cites ISO 9454-1, Soft soldering fluxes - Classification and requirements - Part 1: Classification, labelling and packaging. That standard defines the type 3 fluxes covered by this test method and gives the classification framework used in the scope and bibliography.

What does the oSIST prEN ISO 9455-8:2026 document contain?

oSIST prEN ISO 9455-8:2026 contains a complete laboratory method: the test principle, reagent preparations, apparatus needs, step-by-step procedure, calculation approach, precision statement and reporting items. The procedure is written for triplicate testing and includes handling of iron interference, indicator use and endpoint recognition.

Clause 8 provides the calculation framework for expressing zinc as zinc chloride, using the EDTA consumption and the density of the original sample at 20 °C. Clause 9 summarizes precision from a multi-laboratory study, and Clause 10 tells the user what the test report has to capture for traceability.

SLOVENSKI STANDARD
01-november-2026
Talila za mehko spajkanje - Preskusne metode - 8. del: Določanje cinka (ISO/FDIS
9455-8:2026)
Soft soldering fluxes - Test methods - Part 8: Determination of zinc content (ISO/FDIS
9455-8:2026)
Flussmittel zum Weichlöten - Prüfverfahren - Teil 8: Bestimmung des Zinkgehaltes
(ISO/FDIS 9455-8:2026)
Flux de brasage tendre - Méthodes d'essai - Partie 8: Dosage du zinc (ISO/FDIS 9455-
8:2026)
Ta slovenski standard je istoveten z: prEN ISO 9455-8
ICS:
25.160.50 Trdo in mehko lotanje Brazing and soldering
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

FINAL DRAFT
International
Standard
ISO/FDIS 9455-8
ISO/TC 44/SC 12
Soft soldering fluxes — Test
Secretariat: DIN
methods —
Voting begins on:
2026-09-10
Part 8:
Determination of zinc content
Voting terminates on:
2026-12-03
Flux de brasage tendre — Méthodes d'essai —
Partie 8: Dosage du zinc
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
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MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 9455-8:2026(en) © ISO 2026

FINAL DRAFT
ISO/FDIS 9455-8:2026(en)
International
Standard
ISO/FDIS 9455-8
ISO/TC 44/SC 12
Soft soldering fluxes — Test
Secretariat: DIN
methods —
Voting begins on:
Part 8:
Determination of zinc content
Voting terminates on:
Flux de brasage tendre — Méthodes d'essai —
Partie 8: Dosage du zinc
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 SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
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BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
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Published in Switzerland Reference number
ISO/FDIS 9455-8:2026(en) © ISO 2026

ii
ISO/FDIS 9455-8:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 1
6 Apparatus . 2
7 Procedure . 2
8 Calculation of results . 3
9 Precision . 3
10 Test report . 3
Bibliography . 4

iii
ISO/FDIS 9455-8:2026(en)
Foreword
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