Different systems of color zinc passivation solution, heat resistance performance also varies, this article we will talk about, the difference of heat resistance between trivalent chromium passivation and hexavalent chromium passivation.
Heat resistance of passivation films
Compared with the hexavalent chromium passivation film, the heat resistance of the trivalent chromium passivation film will be better, and when it is above 200℃ and maintained for a long time, the film obtained by using the trivalent chromium color zinc passivation liquid can still maintain the original corrosion resistance of more than 70%.
Particularly suitable for the following two types of parts:
①Parts that need to be used under high temperature conditions, such as engine assemblies and friction parts of automobiles.
②High-strength parts that must undergo high-temperature dehydrogenation after electro-galvanizing.
After the passivation film is heated to more than 80℃ for a few minutes, it is prone to dehydration and cracking, which will expose the galvanized layer, which will reduce the corrosion resistance of the product.
The reason why to compare the heat resistance of trivalent chromium and hexavalent chromium passivation film is in fact to understand its corrosion resistance, in the electrogalvanizing passivation process, an important parameter to test the performance of the film is the corrosion resistance.
There are many factors that affect corrosion resistance, such as water quality, excessive iron impurities in the passivation solution, collisions between workpieces, and the quality of the passivation solution. Bigely color zinc passivation solution BZ-208, obtained trivalent chromium color zinc film appearance uniform color, salt spray comparable to hexvalent chromium yellow passivation corrosion resistance (no need to salt spray), galvanized layer 5 microns, passivation after 96 hours of salt spray test, only a small number of corrosion points.