SIST EN 2437:2004

Aerospace series - Chromate conversion coatings (yellow) for aluminium and aluminium alloys

This standard specifies yellow chromate conversion coating of aluminium and aluminium alloys.
It shall be applicable wherever referenced.

Luft- und Raumfahrt - Gelbchromatieren von Aluminium und Aluminiumlegierungen

Diese Norm legt das Gelbchromatieren von Aluminium und Aluminiumlegierungen fest.
Sie ist anzuwenden, wenn auf sie Bezug genommen wird.

Série aérospatiale - Chromatisation jaune de l'aluminium et des alliages d'aluminium

La présente norme spécifie la chromatation jaune de l'aluminium et des alliages d'aluminium.
Elle doit être appliquée chaque fois qu'elle est citée en référence.

Aerospace series - Chromate conversion coatings (yellow) for aluminium and aluminium alloys

General Information

• Status: Published
• Publication Date: 30-Apr-2004
• ICS: 49.025.20 - Aluminium
• ICS: 49.040 - Coatings and related processes used in aerospace industry
• Technical Committee: I08 - Imaginarni 08
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-May-2004
• Due Date: 01-May-2004
• Completion Date: 01-May-2004
• Ref Project: EN 2437:2001 - Aerospace series - Chromate conversion coatings (yellow) for aluminium and aluminium alloys

Overview

SIST EN 2437:2004 is a European aerospace standard that specifies the requirements for yellow chromate conversion coatings applied to aluminium and aluminium alloys. Developed by the European Committee for Standardization (CEN) and approved by the European Association of Aerospace Manufacturers (AECMA), this standard ensures consistent quality and performance of chromate coatings in aerospace applications. It is applicable wherever referenced in aerospace manufacturing and maintenance processes.

The key function of this standard is to improve corrosion resistance and enhance the adhesion of paints and varnishes on aluminium-based components used in the aerospace industry. SIST EN 2437:2004 covers the entire process, from surface preparation and coating application to inspection and quality assurance.

Key Topics

• Scope and Purpose
  Defines yellow chromate conversion coatings and their application to aluminium alloys. The coatings provide corrosion protection and improve paint adhesion. Type B coatings are also suitable for repairing damaged anodic coatings.

• Classification

  • Type A: Thin coating (0.2–0.42 g/m²) offering slight corrosion resistance with low electrical resistance.
  • Type B: Thicker coating (0.42–1.2 g/m²) offering good corrosion resistance.

• Surface Preparation
  Emphasizes thorough cleaning, degreasing, and pickling to remove contaminants before coating. Processes include alkaline cleaning, abrasive blasting, and acid pickling tailored to alloy type and contamination level.

• Chromate Conversion Coating Application
  Components are immersed or sprayed with a chromate bath, typically containing chromates, fluoride ions, and other additives controlled by strict bath chemistry and temperature guidelines to ensure coating uniformity.

• Post-Coating Treatment
  Rinsing, drying, and rapid overpainting (primer or varnish within 48 hours) prevent degradation of the chromate layer and ensure optimal corrosion resistance.

• Quality Control and Inspection
  Includes visual inspection, measurement of coating mass per unit area, salt spray corrosion testing according to ISO 9227, and adherence to rejection criteria such as defect-free coating and limited corrosion spots.

• Health, Safety, and Environmental Considerations
  Stresses compliance with local regulations regarding chromate chemical handling due to toxicity concerns.

Applications

EN 2437’s yellow chromate coatings are vital in aerospace engineering where aluminium alloys are extensively used-for example, in aircraft skins, structural components, and assemblies. The coatings provide:

• Corrosion Protection
  Essential for prolonging service life of aircraft aluminium exposed to harsh environments.

• Improved Paint Adhesion
  Enhances durability and effectiveness of protective and decorative coatings applied over the chromate layer.

• Repair Solutions
  Suitable for restoring mechanical damage on anodized parts without full reprocessing.

By adhering to SIST EN 2437:2004, aerospace manufacturers and maintenance providers ensure that aluminium parts meet stringent aerospace safety and reliability standards while maintaining consistent surface properties.

Related Standards

• ISO 8081 - Aerospace process for chemical conversion coatings on aluminium alloys: complements EN 2437 by providing general guidelines for conversion coating procedures.

• ISO 9227 - Corrosion tests in artificial atmospheres (salt spray tests): standard test method referenced within EN 2437 for assessing corrosion resistance of coated aluminium parts.

• EN 2000 - Aerospace quality assurance for manufacturers: governs quality system approvals relevant to processors applying chromate conversion coatings.

• EN 2334 - Acid chromate pickling of aluminium and its alloys: covers pre-treatment methods that ensure optimal coating adhesion according to EN 2437 requirements.

• EN 3997 - Specifications for specific aluminium alloys (e.g., AL-P2024-T3) used in aerospace: relevant for material classification within EN 2437.

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Keywords: EN 2437, yellow chromate conversion coating, aluminium alloys, aerospace coatings standard, corrosion resistance, paint adhesion, aerospace surface treatment, chromate coating inspection, aerospace manufacturing standards, aluminium surface preparation.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Aerospace series - Chromate conversion coatings (yellow) for aluminium and aluminium alloysLuft- und Raumfahrt - Gelbchromatieren von Aluminium und AluminiumlegierungenSérie aérospatiale - Chromatisation jaune de l'aluminium et des alliages d'aluminiumAerospace series - Chromate conversion coatings (yellow) for aluminium and aluminium alloys49.040Prevleke in z njimi povezani postopki, ki se uporabljajo v letalski in vesoljski industrijiCoatings and related processes used in aerospace industry49.025.20AluminijAluminiumICS:Ta slovenski standard je istoveten z:EN 2437:2001SIST EN 2437:2004en01-maj-2004SIST EN 2437:2004SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 2437December 2001ICS 49.040English versionAerospace series - Chromate conversion coatings (yellow) foraluminium and aluminium alloysSérie aérospatiale - Chromatation jaune de l'aluminium etdes alliages d'aluminiumLuft- und Raumfahrt - Gelbchromatieren von Aluminiumund AluminiumlegierungenThis European Standard was approved by CEN on 2 May 2001.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the 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 translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2001 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 2437:2001 ESIST EN 2437:2004

a
6 mm 2)4DefinitionsFor the purposes of this standard, the following definition applies:batchparts treated at the same time in the same bath.5Classification5.1Thickness–Type A: Mass per unit area from 0,2 g/m2 to 0,42 g/m2 for slight corrosion protection, where lowelectrical resistance is required;–Type B: Mass per unit area from
0,42 g/m2 to 1,2 g/m2 for good corrosion protection, with or withoutpainting.1)Published as AECMA Standard at the date of publication of this standard2)Published as AECMA Prestandard at the date of publication of this standardSIST EN 2437:2004

3,5 %;–Category 2: Aluminium alloy with an Si-content
3,5 %.6Information for the processor–Designation, see 16.–Areas not to be chromated.7Condition of parts prior to processingSoldering, welding, mechanical operations and heat treatments (except for cold storage) shall be completed.The parts to be chromate coated after assembly (e.g. by spot welding) shall be pickled prior to assembly.Areas not to be chromate coated shall be suitably masked.8Pre-treatment8.1CleaningThe cleaning method shall be chosen according to the degree of contamination of the materials to be treated.In general, the most effective method is degreasing with solvents followed by cleaning in an alkaline solution(see annex A, A.2).8.2RinsingThe parts shall be rinsed thoroughly, e.g. by immersion followed by spray washing. It is recommended that afurther rinsing be carried out in deionised water with a maximum specific conductivity of 100 S
cm–1.8.3PicklingIt shall not cause pitting or any alterations to the metallurgical characteristics or mechanical strength of thematerial.The dimensions and the surfaces roughness value indicated on the drawings shall be observed.Pickling is normally carried out in a solution containing chromate. Other methods may be used (seeannex A, A.4).8.4RinsingSee 8.2.SIST EN 2437:2004
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