By What is difference between trivalent and hexavalent zinc plating?
Trivalent zinc plating is the latest version of zinc plating. The ingredients that we use for this process are chromium sulfate or chromium chloride. On the other hand, hexavalent zinc plating is the older version of zinc plating. The ingredients that we use for this process are chromium trioxide and sulfuric acid.
What color is trivalent chromium?
Trivalent chromium electroplating processes have been commercially available since the mid 1970s. Processes are available today offering deposits with colors varying from gray-black to almost the blue- white appearance of hexavalent chromium.
What is trivalent coating?
Trivalent conversion coatings is used on metals such as aluminum and zinc, and to a lesser extent copper, cadmium, silver, tin, and other metals and their alloys. Trivalent conversion coatings are used to passivate aluminum and as a sealer on metal parts after an iron or zinc phosphate metal finishing process.
What is Blue passivation?
BLUE PASSIVATION. CHROLITE BL – 50. : A blue chromate passivation on zinc coatings for better corrosion resistance.
What color is hexavalent chromium?
What is hexavalent chromium? Chromium is a lustrous, brittle, hard metal. Its colour is silver-grey and it can be highly polished. It does not tarnish in air, when heated it burns and forms the green chromic oxide.
Does zinc plating contain hexavalent chromium?
The substance of concern with regard to chromate conversion coatings on zinc plating and RoHS compliance is hexavalent chromium. The RoHS Directive restricts hexavalent chromium, but does not restrict less hazardous trivalent chromium.
Is trivalent chromium toxic?
Trivalent chromium is an essential trace element in humans and in animals. Chromium as pure metal has no adverse effect. Little toxic effect is attributed to trivalent chromium when present in very large quantities.
Is trivalent chromium a carcinogen?
Present evidence indicates that the trivalent chromium compounds do not cause cancer although high concentrations in some in vitro systems have shown genetic toxicity. Hexavalent chromium compounds cause cancer in humans, in experimental animals and exert genetic toxicity in bacteria and in mammalian cells in vitro.
What is the difference between hexavalent chromium and trivalent chromium?
Hexavalent chromium itself is a hazardous substance and carcinogen and is heavily regulated by the EPA. Trivalent chromium plating uses chromium sulfate or chromium chloride as its main ingredient, instead of chromium trioxide; making trivalent chromium less toxic than hexavalent chromium.
What is the passivation process?
The passivation process is a method of improving the corrosion resistance of stainless steel parts by removing ferrous contaminants like free iron from their surface, restoring them to their original corrosion specifications.
Can passivation be removed?
If you have a manufacturing process which is known to or suspected of depositing contaminant iron, then you need to use a passivation bath to remove it. If your process could not possibly be adding iron, there is no problem.