Marine primer and topcoat - Long-term immersion in seawater without peeling

Ship primer and topcoat, why do ships need to have the difference between primer and topcoat? The primer is the connecting line between the substrate and the topcoat. Some substrates are aluminum and stainless steel, and the topcoat has no adhesion when used directly on them, so we have to use the bottom paint. Ship primer and topcoat, why do ships need primer and topcoat? The primer is the connecting line between the substrate and the topcoat. Some substrates are aluminum and stainless steel, so the topcoat is not adherent to the topcoat directly, so we have to use the bottomcoat. 

There are a lot of marine primer and topcoat products on the market, uneven, want to buy a suitable marine paint, of course, to find experienced Dongguan City Bon Intimate Coating Co.