Galvanized tube surface paint off, why?

Applying achlic paint to the surface of a fire pipe or other galvanized parts will cause the paint film to fall off severely, affecting the anti-corrosion effect and aesthetics. In order to solve this quality defect, the author has repeatedly stressed the need to use phosphate primer primer or zinc yellow primer primer primer, and then paint alkyd paint or alkyd paint. This picture is a typical galvanized tube brush fire alcohol acid big red paint off phenomenon, all galvanized parts of the surface is alkaline, and alkalic paint and zinc-alkali chemical reaction, that is, commonly referred to as saponification reaction, the production of fatty acids, so that the paint film pay effort lost
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. Some people suggest the use of epoxy primer, of course, the cost is higher, and then epoxy primer construction to maintain a certain concentration, not too thick, closed can be, and then paint a variety of color paint alcoholic acid, but whether this will be epoxy and alicic acid effect inverted, especially indoor, epoxy is better than analic acid paint, and outdoor UV-resistant epoxy is not as good as acid paint. Different options for different situations require adjustment and confirmation from the technician.
should say that such errors are common and must be noticed by anti-corrosion design and construction personnel.
Ten birds add a few more points:
1,is more than aolic paint, all oil-based paint (Note: this oil refers to fatty acids) will have this phenomenon, including alcoholic acid and paint, alicic magnetic
/
paint, phenolic and paint, phenolic magnetic
/
paint and so on, because the fatty acids in the oil-based paint will be associated with Zinc reaction, the production of fatty acid zinc (called saponification), zinc fatty acid is a white puffed powdered substance, resulting in the coating and zinc surface in combination with the loss of adhesion and shedding;
2,in addition to
phosphate primer primer or zinc yellow primer primer this solution, can also be designed to use other zinc surface inert primer
to avoid this phenomenon;
3,other paints that can be used on carbon steel surfaces are also not suitable for galvanized surfaces, such as red dan paint, zinc
-rich paint, etc.;Due to the low roughness of the galvanized surface, other inert primers for galvanized surfaces are different from those used for spray-cleaned steel surfaces, mainly for galvanizing surfaces, other inert primers that enhance their adhesion to low-rough surfaces, for example, by adding adhesion promoters
to primer formulations;