Cadmium Substitution - garteur

GARTEUR LIMITED
ANNEX H
Paint adhesion
H.1 Introduction
The adhesion of paint on the different coatings was determined by performing tensile
tests on tapered painted strips and using cross-cut tests. Table H1 summarises the
coatings and tests employed.
H.2 Test procedures
H.2.1
Cross-cut test
Two versions of the cross-cut test were employed.
The cross cut test carried out by Aerospatiale [H1] used a regular square grid pattern.
Tests were conducted on as painted panels and on painted panels, which had been
immersed in de-mineralised water for 14 days. The degree of paint adhesion was
determined by comparing the appearance of the grid after testing with standards given in
ISO 2409-72. Polyurethane Paint System - PAC33 + PU66
The adhesion quality for the paint system on the steel substrate was checked by NLR
using the cross cut test according to NEN 5337 [H2]. A square grid of scribe lines at
increasing distances from 01 to 1.1mm was applied with a sharp chisel on the painted
surface, after which the loose paint blisters were removed with Scotch tape. The degree
of paint adhesion can be expressed in mm delamination. The cross cut tests were
performed on unexposed paint systems and after 7 days immersion in distilled water.
H.2.2
Low temperature tensile test
H.3 Results
The tensile specimen is tapered in the length direction to obtain a gradual plastic strain
distribution along the specimen axis as a result of tensile testing. After testing
macroscopic photographs were made to show the influence of plastic deformation of the
substrate on paint delamination. Cross sections gave information on crack density at
increasing plastic strain. Reference H2 gives details of the dimensions of the tensile
specimens used and the approximate plastic strain distribution after tensile testing.
H.3.1
Cross-cut tests (regular square grid)
Results obtained by Aerospatiale using a regular square grid are presented in table H2.
Adhesion to the electrodeposited aluminium coating was found to be very good. Some
slight loss in adhesion was reported when panels were immersed in distilled water for 14
days. In the case of the Sermetel 984 LT coating, paint adhesion was poor when
samples were immersed in distilled water prior to testing.
H.3.2
Cross-cut tests (variable grid size)
Table H3 summarises the results of the cross-cut tests performed on coated panels that
have been painted. In some instances (coatings 1,3 and 5) only moderate paint adhesion
was recorded. This may be associated with the fact that the paint scheme was not
applied within the specified time following passivation. Excellent paint adhesion was
achieved with coatings 2 and 5 where application of the paint scheme had been carried
out within the required period. The paint adhesion of the Sermetel after one week
GARTEUR SM/AG17 TP128 Page 93