prEN ISO 9455-8

• 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
• Publication Date: 02-Mar-2028
• ICS: 25.160.50 - Brazing and soldering
• Technical Committee: CEN/TC 121 - Welding
• Current Stage: 4020 - Submission to enquiry - Enquiry
• Start Date: 10-Sep-2026
• Completion Date: 10-Sep-2026
• Ref Project: oSIST prEN ISO 9455-8:2026 - Soft soldering fluxes - Test methods - Part 8: Determination of zinc content (ISO/FDIS 9455-8:2026)

• Consolidated By: ISO/FDIS 9455-8 - Soft soldering fluxes — Test methods — Part 8: Determination of zinc content
• Effective Date: 12-Feb-2026
• Revises: EN 29455-8:1993 - Soft soldering fluxes - Test methods - Part 8: Determination of zinc content (ISO 9455-8:1991)
• Effective Date: 13-Aug-2025

prEN ISO 9455-8 is a draft ISO/CEN test method for determining the zinc content of soft soldering fluxes. It is aimed at laboratories and quality control teams that need a repeatable chemical method for water-soluble fluxes of type 3, with results expressed as zinc chloride.

What does prEN ISO 9455-8 specify?

prEN ISO 9455-8 specifies one laboratory method for measuring zinc in soft soldering fluxes, along with the principle, reagents, apparatus, procedure, calculation, precision and test report content. The method is written for water-soluble fluxes of type 3 as defined in ISO 9454-1.

The document is organized into 10 clauses and a bibliography:

• 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

For practice, that means the standard gives the full bench method rather than only a result specification.

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

prEN ISO 9455-8 measures zinc by EDTA titration after preparing the flux in acidic solution, removing any iron precipitation, and using an indicator end point. In use, this is a classical wet-chemical method, so the analyst has to control sample preparation, reagent quality and titration technique carefully.

Scope and sample suitability

The method is intended for an aqueous solution of flux containing approximately 25 % zinc, expressed as zinc chloride. For solid fluxes, or solutions with a different concentration, the sample amount must be adjusted. In practice, users need to match the test portion to the expected zinc level so the titration falls in a workable range.

Chemical principle

Clause 4 states that sulfuric acid is added first, then ammonium chloride, and the solution is made alkaline with ammonia solution. Any iron that precipitates is removed as hydroxide, and zinc is then determined by titration with EDTA. This matters because iron can interfere with the end point, so the method includes a cleanup step before titration.

Reagents and materials

Clause 5 requires analytical-quality reagents and distilled or deionized water. The method uses standard EDTA solution, a pH 10 buffer, sulfuric acid, Eriochrome black T mixture, hydrochloric acid, ascorbic acid, ammonium chloride and ammonia solution. For the laboratory, this means the result depends on using the specified reagent strengths and a fresh indicator mixture.

Procedure and repetition

Clause 7 requires the determination to be carried out in triplicate. The sample is diluted, acidified, transferred to a beaker, alkalized, treated if iron appears, then buffered and titrated to a blue end point. Running the test three times gives a check on consistency and helps the analyst judge whether the method is performing normally.

Calculation and measurement basis

Clause 8 gives the calculation of zinc content as zinc chloride in the original flux sample. The calculation uses the volume of EDTA solution consumed and the density of the original flux sample at 20 °C, measured with a hydrometer. If the sample is solid or a different test portion is used, the calculation has to be adjusted accordingly.

Precision and reporting

Clause 9 summarizes interlaboratory precision work on three zinc-containing fluxes, covering a range from 17 % to 28 % by mass. Clause 10 lists the test report items: sample identification, the method reference, results, unusual features, and any operation not covered by the document or treated as optional. That gives users a standard record for quality files and customer or supplier reporting.

Who uses prEN ISO 9455-8?

prEN ISO 9455-8 is used by testing laboratories, flux manufacturers, quality control departments, and buyers checking incoming soldering materials. It is relevant wherever the zinc content of water-soluble soft soldering fluxes needs to be measured in a traceable, comparable way. The method is particularly useful for product release testing, incoming inspection, and dispute analysis.

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

prEN ISO 9455-8 is the second edition and cancels and replaces ISO 9455-8:1991. The document states that this is a minor revision and that the normative references were updated.

Which standards are used with prEN ISO 9455-8?

ISO 9454-1 is the main companion standard named with prEN ISO 9455-8. It provides the classification and requirements used to define the type 3 water-soluble fluxes covered by the scope.

What does the prEN ISO 9455-8 document contain?

prEN ISO 9455-8 contains a complete test method in clause form, from scope through test report. It gives the chemical principle, reagent preparation, apparatus guidance, step-by-step titration procedure, calculation basis, and a precision statement based on collaborative testing. The document also includes a bibliography entry for ISO 9454-1, which links the method to the flux classification system it uses.

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
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
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
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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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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