SIST EN 4908:2025
(Main)Aerospace series - Hexavalent chromium free chemical conversion process of magnesium and magnesium alloys
Aerospace series - Hexavalent chromium free chemical conversion process of magnesium and magnesium alloys
This document specifies the requirements for the hexavalent chromium free chemical conversion process of magnesium and magnesium alloys to ensure an adhesion base before bonding and painting.
The purpose of this document is to specify design, quality and manufacturing requirements. It does not specify complete in-house process instructions; these are specified in the processors detailed process instructions.
Luft- und Raumfahrt - Chrom(VI)-freies chemisches Umwandlungsverfahren von Magnesium und Magnesiumlegierungen
Série aérospatiale - Procédé de conversion chimique sans chrome hexavalent du magnésium et des alliages de magnésium
Le présent document spécifie les exigences relatives au procédé de conversion chimique sans chrome hexavalent du magnésium et des alliages de magnésium permettant d’assurer une base d'adhérence avant le collage et la peinture.
L’objet du présent document est de spécifier les exigences de conception, de qualité et de fabrication. Il ne spécifie pas de gamme de production complète ; ces informations sont spécifiées dans les instructions détaillées de l’applicateur relatives au procédé.
Aeronavtika - Postopek kemične pretvorbe magnezija in magnezijevih zlitin brez šestvalentnega kroma
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-februar-2025
Aeronavtika - Postopek kemične pretvorbe magnezija in magnezijevih zlitin brez
šestvalentnega kroma
Aerospace series - Hexavalent chromium free chemical conversion process of
magnesium and magnesium alloys
Luft- und Raumfahrt - Chrom(VI)-freies chemisches Umwandlungsverfahren von
Magnesium und Magnesiumlegierungen
Série aérospatiale - Procédé de conversion chimique sans chrome hexavalent du
magnésium et des alliages de magnésium
Ta slovenski standard je istoveten z: EN 4908:2024
ICS:
49.025.15 Neželezove zlitine na Non-ferrous alloys in general
splošno
77.120.20 Magnezij in magnezijeve Magnesium and magnesium
zlitine alloys
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN 4908
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2024
EUROPÄISCHE NORM
ICS 49.025.15
English Version
Aerospace series - Hexavalent chromium free chemical
conversion process of magnesium and magnesium alloys
Série aérospatiale - Procédé de conversion chimique Luft- und Raumfahrt - Chrom(VI)-freies chemisches
sans chrome hexavalent du magnésium et des alliages Umwandlungsverfahren von Magnesium und
de magnesium Magnesiumlegierungen
This European Standard was approved by CEN on 3 June 2024.
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, Türkiye 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
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 4908:2024 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 General principle of the process . 5
4.1 Purpose of the process . 5
4.2 Limitations . 5
5 Process requirements . 5
5.1 Information for the processor . 5
5.2 Process schedule . 5
5.3 Process conditions . 6
5.4 Reworks . 7
5.5 Removal . 7
6 Test specimens — requirements. 8
6.1 Test specimens — specification . 8
Table 1 — Qualification and periodic testing test specimens requirements . 8
6.2 Qualification tests . 8
6.3 Periodic testing . 8
7 Parts requirements . 8
7.1 Sampling plan for serial inspections . 8
Table 2 — Sampling plan for serial production . 9
7.2 Inspection on parts after treatment . 9
8 Quality assurance . 9
8.1 Process approval . 9
8.2 General points . 9
Annex A (normative) Tests on test specimens for the qualification and for periodic testing . 11
Table A.1 — Qualification and periodic testing. 11
Annex B (normative) Tests on parts . 13
Table B.1 — Serial production testing . 13
Annex C (normative) Acceptance criteria after corrosion test . 14
Figure C.1 — Salt spray acceptance criteria . 14
European foreword
This document (EN 4908:2024) has been prepared by ASD-STAN.
After enquiries and votes carried out in accordance with the rules of this Association, this document has
received the approval of the National Associations and the Official Services of the member countries of
ASD-STAN, prior to its presentation to CEN.
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 June 2025, and conflicting national standards shall be
withdrawn at the latest by June 2025.
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.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
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, Türkiye and the
United Kingdom.
1 Scope
This document specifies the requirements for the hexavalent chromium free chemical conversion
process of magnesium and magnesium alloys to ensure an adhesion base before bonding and painting.
The purpose of this document is to specify design, quality and manufacturing requirements. It does not
specify complete in-house process instructions; these are specified in the processors detailed process
instructions.
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.
EN 4902, Aerospace series — Surface treatments — Definitions and test methods
EN ISO 2409, Paints and varnishes — Cross-cut test (ISO 2409)
EN ISO 2812-2, Paints and varnishes — Determination of resistance to liquids — Part 2: Water immersion
method (ISO 2812-2)
EN ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests (ISO 9227)
ASTM B117, Standard Practice for Operating Salt Spray (Fog) Apparatus
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 4902 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1
OEM
producer who has the design authority and manufactures products or components that are purchased
by a company and retailed under that purchasing company’s brand name
Note 1 to entry: The OEM can also apply the process.
3.2
manufacturer
company or person who makes, manufactures, assembles components
Note 1 to entry: The manufacturer can also apply the process.
3.3
processor
company or person who applies the process
Published by ASTM International, available at: https://www.astm.org/.
3.4
process instruction
document that describes the application scopes, detailed process (e.g., key parameters, detailed steps),
quality management, environmental and safety regulations
3.5
batch
unless otherwise specified, it comprises parts of the same type (i.e., shape, size, material), processed at
the same time in the same bath
4 General principle of the process
4.1 Purpose of the process
The treatment consists of a superficial chemical transformation of the magnesium alloy parts obtained
by hexavalent chromium free chemical conversion process.
It is used to ensure an adhesion base before bonding and painting.
It is used either for local application or by immersion.
4.2 Limitations
All the heat treatment, shaping, brazing, welding and machining operations shall be carried out before
chemical conversion of the parts.
Before applying the conversion process, the surfaces of the parts shall be free from etching and
corrosion pitting.
5 Process requirements
5.1 Information for the processor
— Part number;
— quantity of parts to be processed;
— alloy to be processed.
5.2 Process schedule
It shall, as a minimum, have the following steps:
— alkaline degreasing;
— pickling;
— phosphate and permanganate based chemical conversion;
— post-treatment (such as paint, as per the requirement of the drawing).
5.3 Process conditions
5.3.1 Tooling
The tools, bars, and metal masking tooling shall be free of oxidation/corrosion or any other damage
which may be detrimental to the treatment during use. The part racks and tools shall be designed and
set up in such a manner as to:
— avoid any retention of air or treatment solution in the parts;
— facilitate neutralization and removal of solutions during rinsing operations;
— remain inert and not contaminate solutions of the process.
5.3.2 Masking
The parts shall be at least degreased prior to masking.
Component areas which shall not be coated shall be masked with suitable material.
The areas of the assemblies containing parts made of materials other than magnesium and its alloys
shall be masked during the chemical conversion treatment.
5.3.3 Surface preparation
5.3.3.1 Degreasing
Before applying the conversion process, the surfaces of the parts shall be clean, perfectly wettable.
The key operating parameters (e.g. nature of the product, temperature, time, pH) shall be set in a
procedure that will be approved by the OEM.
5.3.3.2 Mechanical preparation
For local applications where parts are prepared by mechanical surface roughening, a rinsing with
deionized water shall be performed to remove contamination (abrasive residues) from the surface to be
processed.
The key operating parameters (nature of the product and operating method) shall be set in a procedure
that will be approved by the OEM.
5.3.3.3 Chemical pickling
For magnesium alloys with silver, a specific preparation is recommended depending on the process
applied.
The stripping should be carried out using a solution without hexavalent chromium.
The pickling carried out shall make it possible to remove the natural oxides in order to obtain a correct
chem
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