Aerospace series - Hexavalent chromium free anodizing of aluminium and aluminium alloys

This document defines the requirements for hexavalent chromium free anodizing of aluminium and aluminium alloys for corrosion protection, bonding and painting.
Hard anodizing and plasma electrolytic anodizing (micro-arc oxidation) are not covered by this document.
The purpose of this document is to give design, quality and manufacturing requirements. It does not give complete in-house process instructions; these are given in the processors detailed process instructions.

Luft- und Raumfahrt - Anodisieren von Aluminium und Aluminiumlegierungen ohne hexavalentem Chrom

Dieses Dokument legt die Anforderungen für das Chrom-VI-freie Anodisieren von Aluminium und Aluminiumlegierungen zum Schutz vor Korrosion sowie zum Kleben und Lackieren fest.
Das Hartanodisieren und das Anodisieren mithilfe von Plasmaelektrolyten (Mikro-Lichtbogen-Oxidation) werden von dieser Europäischen Norm nicht abgedeckt.
Zweck dieses Dokuments ist die Vorgabe von Leistungs-, Qualitäts- und Herstellungsanforderungen. Es stellt keine vollständigen innerbetrieblichen Prozessanweisungen zur Verfügung; diese sind in den ausführlichen Prozessanweisungen der Bearbeiter angegeben.

Série aérospatiale - Anodisation sans chrome hexavalent de l'aluminium et des alliages d'aluminium

Aeronavtika - Šestvalentni krom brez eloksacije aluminija in aluminijevih zlitin

Ta dokument določa zahteve za šestvalentni krom brez eloksacije aluminija in aluminijevih zlitin za zaščito proti koroziji, spajanje ter barvanje. Ta dokument ne zajema trde eloksacije in plazemske elektrolitske eloksacije (oksidacije z mikro oblokom). Namen tega dokumenta je določiti zahteve glede zasnove, kakovosti in proizvodnje. Ne podaja popolnih navodil glede internega procesa, ki bodo podana v izvajalčevih podrobnih navodilih glede procesa.

General Information

Status
Published
Publication Date
24-Sep-2019
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
25-Sep-2019
Completion Date
25-Sep-2019

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SLOVENSKI STANDARD
SIST EN 4827:2019
01-december-2019
Nadomešča:
SIST EN 4827:2017
Aeronavtika - Šestvalentni krom brez eloksacije aluminija in aluminijevih zlitin
Aerospace series - Hexavalent chromium free anodizing of aluminium and aluminium
alloys
Luft- und Raumfahrt - Anodisieren von Aluminium und Aluminiumlegierungen ohne
hexavalentem Chrom

Série aérospatiale Anodisation sans chrome hexavalent de l'aluminium et des alliages

d'aluminium
Ta slovenski standard je istoveten z: EN 4827:2019
ICS:
49.025.99 Drugi materiali Other materials
SIST EN 4827:2019 en,fr,de

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

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SIST EN 4827:2019
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SIST EN 4827:2019
EN 4827
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2019
EUROPÄISCHE NORM
ICS 49.025.20; 49.040 Supersedes EN 4827:2017
English Version
Aerospace series - Hexavalent chromium free anodizing of
aluminium and aluminium alloys

Série aérospatiale - Anodisation sans chrome Luft- und Raumfahrt - Anodisieren von Aluminium und

hexavalent de l'aluminium et des alliages d'aluminium Aluminiumlegierungen ohne hexavalentem Chrom

This European Standard was approved by CEN on 14 July 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 4827:2019 E

worldwide for CEN national Members.
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SIST EN 4827:2019
EN 4827:2019 (E)
Contents Page

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

1 Scope .......................................................................................................................................................... 4

2 Normative references .......................................................................................................................... 4

3 Terms and definitions ......................................................................................................................... 5

4 General principles of the process .................................................................................................... 6

5 Process requirements ......................................................................................................................... 8

6 Engineering requirements .............................................................................................................. 11

7 Quality requirements ........................................................................................................................ 13

Annex A (normative) Engineering requirements ................................................................................... 15

Annex B (normative) Quality requirements ............................................................................................ 16

B.1 Quality requirements ........................................................................................................................ 16

B.2 Dye-spot test ......................................................................................................................................... 17

Annex C (informative) Standard evolution form .................................................................................... 20

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SIST EN 4827:2019
EN 4827:2019 (E)
European foreword

This document (EN 4827:2019) has been prepared by the Aerospace and Defence Industries Association

of Europe - Standardization (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, prior to its presentation to CEN.

This document shall be given the status of a national standard, either by publication of an identical text

or by endorsement, at the latest by March 2020, and conflicting national standards shall be withdrawn at

the latest by March 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 4827:2017.

According to the CEN-CENELEC Internal Regulations, the national standards organisations 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.
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SIST EN 4827:2019
EN 4827:2019 (E)
1 Scope

This document defines the requirements for hexavalent chromium free anodizing of aluminium and

aluminium alloys for corrosion protection, bonding and painting.

Hard anodizing and plasma electrolytic anodizing (micro-arc oxidation) are not covered by this

document.

The purpose of this document is to give design, quality and manufacturing requirements. It does not give

complete in-house process instructions; these are given 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 2284, Aerospace series — Sulphuric acid anodizing of aluminium and wrought aluminium alloys

EN 3665, Aerospace series — Test methods for paints and varnishes — Filiform corrosion resistance test on

aluminium alloys

EN 4704, Aerospace series — Tartaric-Sulphuric-Acid anodizing of aluminium and aluminium wrought

alloys for corrosion protection and paint pre-treatment (TSA)

EN 4707, Aerospace series — Acid pickling of aluminium and aluminium alloy without hexavalent

chromium

EN 6072, Aerospace series — Metallic materials — Test methods — Constant amplitude fatigue testing

EN ISO 1463, Metallic and oxide coatings — Measurement of coating thickness — Microscopical method

EN ISO 2085, Anodizing of aluminium and its alloys — Check for continuity of thin anodic oxidation

coatings — Copper sulfate test

EN ISO 2360, Non-conductive coatings on non-magnetic electrically conductive base metals —

Measurement of coating thickness — Amplitude-sensitive eddy-current method
EN ISO 2409, Paints and varnishes — Cross-cut test

EN ISO 9220, Metallic coatings — Measurement of coating thickness — Scanning electron microscope

method
EN ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests

EN ISO 10289, Methods for corrosion testing of metallic and other inorganic coatings on metallic

substrates — Rating of test specimens and manufactured articles subjected to corrosion tests

1) Published as ASD-STAN Prestandard at the date of publication of this standard by AeroSpace and Defence

industries Association of Europe - Standardization (ASD-STAN), http://www.asd-stan.org/

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SIST EN 4827:2019
EN 4827:2019 (E)
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 http://www.iso.org/obp
 IEC Electropedia: available at http://www.electropedia.org/
3.1 General terms
3.1.1
OEM

producer who 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.
3.1.2
manufacturer
company or person who makes, fabricates, assembles components
Note 1 to entry: The manufacturer can also apply the process.
3.1.3
processor
company or person who applies the process
3.1.4
process instruction

document that describes the application scopes, detailed process (key parameters, detailed steps, etc.),

quality management, environmental and safety regulations, etc.
3.1.5
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
3.2 Technical terms
3.2.1
de-anodizing
process, which removes the anodic oxide
3.2.2
smut

precipitations of alloying elements (e.g. Cu, Fe, Zn, Si) on the surface of parts after a process step normally

after alkaline etching step
3.2.3
Mechanically Disturbed Layer
MDL

layer that is present at the surface resulting from the rolling process of the material

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SIST EN 4827:2019
EN 4827:2019 (E)
3.2.4
pit

surface corrosion defect at which the anodic coating is penetrated and/or perforated

Note 1 to entry: Typical characteristics of corrosion pits are:
 rounded or irregular or elongated geometry,
 tail or line or halo that emerges from the cavity,

 some corrosion by-products inside pits (on aluminium the by-product may be granular,

powdery or amorphous and white, grey or black in colour).

To be considered as a corrosion pit, a surface cavity shall exhibit at least two of the above characteristics.

3.2.5
re-anodizing
repetition of the anodizing process step after complete de-anodizing
3.2.6
sealing

chromate VI free sealing (of the anodized layers) is applied to close the pores produced by the acid

anodizing process

Note 1 to entry: It is usually applied in hot demineralized water bath with or without additives at different

temperatures. Sealing improves the corrosion resistance performance of the anodic film.

4 General principles of the process
4.1 Purpose of the process

The anodizing is an electrochemical process voltage controlled allowing transforming the aluminium

(and its alloys) surface in a nanoporous and amorphous oxide layer made of a structure close to alumina.

The aim of this treatment is to ensure a protection against the corrosion, and/or to be used as an adhesion

base before bonding or before painting. Anodizing is generally sealed for corrosion protection application

(with or without painting or bonding) and can remain unsealed when the part is bonded or painted.

This specification is applicable on aluminium and aluminium alloys generally on single parts.

Hard anodizing and plasma electrolytic anodizing (micro-arc oxidation) dedicated to wear protection are

not covered by this specification.
4.2 Applicability
4.2.1 Type A: unsealed anodizing

It shall be used either as surface preparation before the application of painting/bonding or any other

finishing.
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SIST EN 4827:2019
EN 4827:2019 (E)
4.2.2 Type B: sealed anodizing

It is intended for corrosion protection. It shall be with or without dyeing and used with or without

additional painting.
Table 1 — Different application cases
Unsealed (type A) Sealed (type B)
Bonding
Unpainted Painted Unpainted Painted
(structural)
Sulphuric acid
anodizing (SAA)
EN 2284
Applicable
Thin film sulphuric acid
anodizing (TFSAA)
Not applicable Applicable
Not defined
Tartaric sulphuric acid
yet with
anodizing (TSA)
chromate VI
Not applicable Applicable
EN 4704
free sealing
Boric sulphuric acid
anodizing (BSAA)
Phosphoric acid anodizing
Not applicable
(PAA)
Applicable Not applicable
Sulphuric phosphoric acid
anodizing (PSA)
4.3 Limitations

All processes that can compromise the anodic film such as forming, or heat-treatment shall be performed

prior to surface preparation of the parts to be anodized.
Anodizing shall not be applied:
 in electric conductivity zones/areas;

 for tubes, pipes and open holes with a length to diameter ratio higher than 10:1 (unless using specific

cathode);
 for trapped holes with a length to a diameter ratio greater than 5:1;

 for parts or assemblies (e.g. spot-welded and riveted), which can permanently entrap treatment

solutions;

 for components which can permanently entrap treatment solutions, except components that can be

adequately masked.

NOTE The formation of oxide layer influences the dimensions of the part and is to be considered for close

tolerance parts.
4.4 Protection system classification
4.4.1 System types
Anodizing layer is classified by the two following types:
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SIST EN 4827:2019
EN 4827:2019 (E)

 type A: unsealed anodizing: It shall be used as surface preparation before the application of painting/

bonding or any other finish;

 type B: sealed anodizing: It is intended for corrosion protection. It shall be with or without dyeing

and used with or without additional painting.
4.4.2 Layer thickness
See Table 2.
Table 2 — Layer thicknesses corresponding to the class type
Class type Typical thickness Anodizing process
Phosphoric acid anodizing (PAA)
Class 1 ≤ 1 µm
Sulphuric phosphoric acid anodizing (PSA)
Tartaric sulphuric acid anodizing (TSA)
Class 2 2 µm to 8 µm Boric sulphuric acid anodizing (BSAA)
Thin film sulphuric acid anodizing (TFSAA)
Class 3 8 µm to 25 µm Sulphuric acid anodizing (SAA)

≤ 5 µm for some aluminium alloys under agreement between the processor and the OEM/manufacturer.

5 Process requirements
5.1 Information for the processor
 type and class designation,
 substrate standard reference and heat treatment,
 areas to be anodized,
 anodizing thickness measuring points,
 electrical contact points or areas where these are inadmissible,
 specification for testing on parts and/or samples.
5.2 Condition of parts prior to the treatment

Welding, soldering/brazing, mechanical operations and heat treatments shall have been completed.

 the parts shall be free of oil, grease, marking inks and other surface contaminations;

 the surface shall be free from precipitations or smut from alloying elements or pre-processes

indicated by the bright and uniform appearance of the surface;

 mechanically disturbed layer shall be removed either by mechanical or chemical processes;

 in case of re-anodizing all residuals from the previous anodizing shall be completely removed.

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SIST EN 4827:2019
EN 4827:2019 (E)
5.3 Process conditions
5.3.1 Tooling

The tools, bars, electrical contact systems, 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,

 the electrical contacts shall be kept in good condition for the correct passage of the current,

 electrical contact points should be defined between the processor and the OEM/manufacturer,

 the contact is preferably achieved at several points in order to ensure better current distribution,

 avoid any accidental contact between the parts to be treated and the tank equipment or electrodes,

and between the different parts during all the process,

 the fixturing tools (e.g. made of aluminium alloy or titanium) shall provide effective electrical contact

with the parts.
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.

5.3.3 Surface pre-treatment

Surface preparation means any method able to eliminate completely all surface contaminations.

In case of chemical pre-treatment, the final step prior to anodizing shall be acidic pickling, preferably

chromate-free.

Anodizing shall be performed immediately after pickling (in accordance with aluminium and aluminium

alloys pickling standard EN 4707).
5.3.4 Anodizing
During the anodizing process:

 distance between electrode and parts and between parts shall be adopted to avoid damage of parts

by short-circuits and electric arc discharge ;
 parts should be fully immersed;

 the parts shall not be subjected to any tensile, flexure, torsion or other stress;

 the process shall be performed in such a way that parts remain wet between each step of the process;

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SIST EN 4827:2019
EN 4827:2019 (E)

 the anodizing parameters (temperature, voltage, time) shall be adapted to the material and to the

chemical composition of the bath;

 in case of re-anodizing, the former protection will have to be totally removed before (chemically or

mechanically) (see 5.5).
5.3.5 Anodizing post-treatments
After the anodizing procedure:
 parts have to be adequately rinsed with water according to 5.4.3;
 afterwards, the parts shall be either:

 dried immediately afterwards and painted within 16 h; this time can be extended in accordance

with customer the OEM/manufacturer requirements. In this case, it is recommended to handle

the parts after anodizing treatment with gloves.

 dried immediately afterwards and bonded within 8 h; this time can be extended in accordance

with customer the OEM/manufacturer requirements. In this case, it is recommended to handle

the parts after anodizing treatment with gloves.

 sealed with chromate VI free solution to achieve the desired corrosion resistance of the anodic

film.
5.4 Water quality

All water used for bath make-up and addition in the anodizing bath, for the final rinsing step as well as

for the sealing process shall be demineralized.
5.4.1 Anodizing bath
The water shall comply with the following requirements:
 pH value at 25 °C: 5,0 to 8,0
 total residue [mg/l]:  5
 conductivity [µS/cm]:  20
5.4.2 Sealing and dyeing baths
The water shall comply with the following requirements:
 pH value at 25 °C: 5,0 to 8,0
...

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