1.2.4 HDG - Painting Issues PDF
1.2.4 HDG - Painting Issues PDF
1.2.4 HDG - Painting Issues PDF
Due to the process of hot dip galvanising, a large variation in the nature and
condition of the surface can occur. This can affect the performance and
appearance of an applied coating system.
Corrosion products or soluble salts left on the surface prior to painting can serve to
draw moisture through the paint film, accelerating corrosion and leading to
blistering (commonly known as “osmotic blistering").
The surface of HDG steel is usually quite smooth. As with all good coating practices
the removal of contaminants that may interfere with adhesion must be carried out
along with the mechanical abrasion (using non-metallic abrasive) to maximise
mechanical and chemical adhesion. Please refer to Dulux Protective Coatings
Tech Note 1.2.2 ‘Surface Preparation Issues’ and Dulux Protective
Coatings Tech Note 1.2.3 ‘Preferred Surface Preparation Methods’
that discuss the preparation of HDG steel for painting.
Typical products used to coat HDG steel include water-based acrylics, vinyl butyrate etch primers, solution vinyls and
epoxies. The choice of product type is dictated by the environment and the performance expectations of the
coating system.
For specification advice, please contact the Dulux Protective Coatings Technical Consultant in your state.
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Saponification - Breakdown of a paint film resulting from the reaction of alkali (galvanised surface) on the binder medium (resin) in
paint. This reaction forms a soap film that will cause softness and loss of adhesion of the coating.