EN 4827:2019

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

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.

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

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.
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
1)
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/
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
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.
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:
 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
a
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
...