FprEN 4473

SLOVENSKI STANDARD
oSIST prEN 4473:2023
01-maj-2023
Aeronavtika - Organski premazi, pigmentirani z aluminijem, za vezne elemente -
Tehnična specifikacija
Aerospace series - Aluminium pigmented organic coatings for fasteners - Technical
specification
Luft und Raumfahrt - Aluminium pigmenttete organische Beschichtungen für
Verbindungselemente - Technische Lieferbedingungen
Série aérospatiale - Revêtements alumino-organiques pour éléments de fixation -
Spécification technique
Ta slovenski standard je istoveten z: prEN 4473
ICS:
49.025.20 Aluminij Aluminium
49.030.01 Vezni elementi na splošno Fasteners in general
49.040 Prevleke in z njimi povezani Coatings and related
postopki, ki se uporabljajo v processes used in aerospace
letalski in vesoljski industriji industry
oSIST prEN 4473:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 4473:2023
oSIST prEN 4473:2023
DRAFT
EUROPEAN STANDARD
prEN 4473
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2023
ICS 49.040 Will supersede EN 4473:2010
English Version
Aerospace series - Aluminium pigmented organic coatings
for fasteners - Technical specification
Série aérospatiale - Revêtements alumino organiques Luft und Raumfahrt - Aluminium pigmenttete
pour pièces de fixations - Spécification technique organische Beschichtungen für Verbindungselemente -
Technische Lieferbedingungen
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee ASD-
STAN.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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.
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 supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 4473:2023 E
worldwide for CEN national Members.

oSIST prEN 4473:2023
prEN 4473:2023 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Technical requirements . 6
4.1 General. 6
4.2 Classification. 6
4.3 Product composition and application . 6
4.4 Coating performance . 6
Annex A (normative) Performance requirements . 8
Annex B (normative) Test coupons for galvanic compatibility . 13
Annex C (normative) Test coupons for paint adhesion . 14
Annex D (normative) Test coupons for electrical conductivity tests . 15
Bibliography . 16

oSIST prEN 4473:2023
prEN 4473:2023 (E)
European foreword
This document (prEN 4473:2023) 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-STAN, prior to its presentation to CEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 4473:2010.
The main changes compared to the previous edition are as follows:
— re-write to new layout;
— clarify some test requirements, e.g. coating adhesion on fasteners, measurement of coating
thickness.
oSIST prEN 4473:2023
prEN 4473:2023 (E)
1 Scope
This document defines the performance requirements for aluminium pigmented organic coatings to be
applied on titanium, titanium alloys, nickel or cobalt based alloys and corrosion resistant steels.
This specification does not cover electrical bonding and lightning strike applications of this coating.
Additional qualification tests will be agreed with the OEM upon qualification.
NOTE This coating is not recommended for use on non-corrosion resistant steel fasteners.
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 4474, Aerospace series - Aluminium pigmented coatings - Coating methods
prEN 6117, Aerospace series — Specification for lubrication of fasteners with acetyl alcohol
EN ISO 2812-1, Paints and varnishes - Determination of resistance to liquids - Part 1: Immersion in liquids
other than water (ISO 2812-1)
ISO 2409, Paints and varnishes — Cross-cut test
ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests
ASTM B117, Standard Practice for Operating Salt Spray (Fog) Apparatus
MIL-A-8625, Anodic coatings for aluminium and aluminium alloys
NASM 1312-5, Fastener Test Methods; Method 5: Stress durability
NASM 1312-12, Fasteners Test Methods, Method 12: Thickness of metallic coatings
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
production lot
parts subjected to the same aluminium pigmented coating application at the same time under the same
condition
Published as ASD-STAN Prestandard at the date of publication of this standard by AeroSpace and Defence
Industries Association of Europe – Standardization (ASD-STAN) (www.asd-stan.org).
Published by: Department of Defense (DOD), the Pentagon, Washington, D.C. 20301 USA.
Published by: Aerospace Industries Association, 1000 Wilson Boulevard, Suite 1700, Arlington, VA 22209-
3928, USA.
oSIST prEN 4473:2023
prEN 4473:2023 (E)
3.2
product
commercial chemical solution that constitutes the aluminium pigmented coating
3.3
blister
local convexity caused by a sub-surface inclusion of gas or liquid
3.4
nodule
localized build-up or unmixed solid particles
3.5
pit
void, hole in the surface as caused, for example, by corrosion
3.6
porosity
fine holes or pores within the coating
3.7
functional surfaces
defined as surfaces in contact with mating structure and threaded portion such as:
— pins, bolts, lockbolts, screws: under head bearing surface, shank, lead-in radius and thread surface
if applicable;
— nuts, threaded collars: bearing surfaces, thread surface;
— spherical washers: bearing surfaces;
— swaged collars: all surfaces
3.8
generic part
family of similar fasteners such as:
— pins, bolts, screws and lockbolts;
— nuts and threaded collars;
— swaged collars;
— solid rivets;
— blind bolts;
— bushes;
— washers
oSIST prEN 4473:2023
prEN 4473:2023 (E)
4 Technical requirements
4.1 General
This document covers organic resin coatings pigmented with aluminium powder. Aluminium
pigmented coatings provide:
— Friction reduction in threads and interference fit assemblies;
— Galvanic corrosion protection between fasteners and the structure in which the fasteners are
installed;
— Protection against aggressive chemicals used in operations and maintenance.
TR 4676 provides a list of commercial aluminium pigmented coating products widely used in the
aerospace industry. This list is non-exhaustive and the use of different products may vary for each OEM
and their specific applications.
4.2 Classification
Aluminium pigmented coatings are classified according to the following types:
Type I: Aluminium pigmented coatings containing hexavalent chromium, for use with cetyl
alcohol.
Type II: Hexavalent chromium free aluminium pigmented coatings, for use with cetyl alcohol.
Aluminium pigmented coatings containing hexavalent chromium, for use without
Type III:
lubricant.
Type IV: Hexavalent chromium free aluminium pigmented coatings, for use without lubricant.
If no dedicated type is specified in the drawing, type II or IV shall be used depending on the need for
lubrication (to be confirmed with the OEM).
4.3 Product composition and application
The manufacturing method and product composition is defined by the product manufacturer. The latter
should peremptorily notify its users of any change subsequent to qualification.
The product shall not contain lead or graphite. Type II and IV shall not contain hexavalent chromium.
Unless otherwise specified, product application shall be carried out in accordance with EN 4474.
4.4 Coating performance
a) Qualification of a new coating product as per EN 4473.
Qualification tests as per Table A.1 shall be performed to each individual coating product-material
type (e.g. titanium alloys, corrosion resistant steels, Ni and Co-based alloys), combination with the
mandated body, unless otherwise specified.
b) Qualification of fasteners or other parts coated with a qualified coating product as per EN 4473.
Unless otherwise specified, qualification tests shall be performed as per Table A.1.
All the tests required by this paragraph shall be carried out on coated fasteners, unless otherwise
agreed with the mandated body.
oSIST prEN 4473:2023
prEN 4473:2023 (E)
c) Lot release of qualified fasteners or other parts coated with a qualified coating product as per
EN 4473.
Each lot of coated fasteners (or other parts) manufactured shall be subject to the acceptance tests
and sampling devised in EN 4474 by the supplier before delivery. The results of these tests shall be
given on the acceptance report for each lot of coated fastener (or other parts).
oSIST prEN 4473:2023
prEN 4473:2023 (E)
Annex A
(normative)
Performance requirements
Table A.1 — (continuous)
Acceptance criteria
Quantity of
Characteristic Inspection Required
(all test parts shall
test parts
conform)
A1.1 Visual examination The coating shall be a), b) 10
smooth, uniform colour,
Appearance
and shall be free of
pinholes, porosity, blisters,
nodules, pits, or other
imperfections.
A1.2 Determination of coating Parts with external a), b) 10
thickness shall be made by any functional surfaces only:
Thickness
of the methods specified in
The coating thickness shall
NASM 1312-12.
be between 5 μm and
In case of conflict, the 13 μm on all functional
micrographic examination shall surfaces as defined in 3.7.
be chosen.
Parts with external and
internal functional
surfaces:
The coating thickness shall
be between 5 μm and
20 μm on all functional
surfaces as defined in 3.7.
A1.3 ISO 2409 – Tape method The coating shall remain a), b) 5
continuously bonded to
Adhesion If the fastener geometry does
the base material.
not allow the ISO2409 cross-
cut, the coating shall be cut EN ISO 2409 Class 0.
through to the base material on
the largest plain surface of the
part using a sharp cutter. Press
the tape firmly to the cut on the
plain surface of the fastener
and remove the tape in one
abrupt motion perpendicular
to the fastener surface.
Any evidence of coating
separation when examined at
4X magnification is cause for
rejection.
oSIST prEN 4473:2023
prEN 4473:2023 (E)
Acceptance criteria
Quantity of
Characteristic Inspection Required
(all test parts shall
test parts
conform)
A1.4 Expose the coated fasteners to The coating shall not show a) 4
315 ± 10°C for 4 h. Air cool at evidence of flaking,
Heat resistance
ambient temperature. powdering, blistering or
...