Performance comparison of different coatings
There are two most important factors for the choice of primer.
One considers the adhesion of primers and topcoats and substrates.
The second is that the primer provides most of the corrosion resistance of the coating.
From this perspective, epoxy resin is the best choice.
If you consider flexibility and UV resistance, you can also choose polyurethane primer.
For the back coating, the most correct choice is to choose a two-layer structure,
that is, a back primer and a back top coat if the color-coated steel sheet is used in a single board.
The primer is of the same variety as the front and a layer of light color (such as white) polyester select for the topcoat.
If the color-coated steel sheet is used in a composite or sandwich panel,
coat the back with a layer of epoxy resin with excellent adhesion and corrosion resistance.
Coating gloss selection
The level of gloss is not a performance index of the coating, it is just a sign like the color.
In fact, paint (coating) is easier to achieve high gloss.
However, the high-gloss surface is dazzling and the high reflectivity of sunlight during the day will cause light pollution (many of the glass curtain walls do not use now because of light pollution).
In addition, the high-gloss surface has a low coefficient of friction and is easy to slip.
It is easy to bring safety hazards during roof construction.
The aging of the color-coated steel plate, when used outdoors, is the first sign of loss of gloss.
When repairs are required, it is easy to distinguish between old and new steel plates, resulting in poor appearance.
If the back paint is high-gloss, it is easy to produce halo when there is light in the room,
which may cause visual fatigue of the personnel.
Therefore, under normal circumstances, color-coated steel sheets for construction use medium and low gloss (30-40 degrees).