Electro-galvanisation

Galvanizing, also known in the industry as water galvanizing, is the process of using electrolysis to form a uniform, dense, well-bonded deposit of zinc or zinc alloy on the surface of a component.

Compared with other metals, zinc is relatively inexpensive and easy to coat. It is a low-value anti-corrosion coating commonly used to protect steel parts, particularly against atmospheric corrosion, and for decorative purposes.

Zinc is chemically active with respect to iron, so the galvanized layer on iron is sacrificial (i.e. a corrosive anode) with respect to the iron substrate. When exposed to a corrosive environment, the zinc layer is more likely to lose electrons than the iron, so galvanizing provides electrochemical protection for the steel substrate. Galvanizing therefore provides electrochemical protection for the steel substrate, which is thus protected against rust.

Characteristics of galvanizing

Galvanizing is generally divided into two categories: alkaline galvanizing and acid galvanizing. Alkaline galvanizing includes cyanide-free alkaline galvanizing and cyanide galvanizing; acid galvanizing includes potassium chloride galvanizing, sodium chloride galvanizing and ammonium chloride galvanizing. Galvanic passivation is divided into hexavalent chromium passivation and trivalent chromium passivation. At present, cyanide galvanizing and hexavalent chromium passivation, which are highly toxic and heavy-metal-based processes, have been eliminated from the market.

Take, for example, our passivation products for environmentally-friendly galvanizing agents, including cyanide-free alkaline zinc, potassium chloride galvanizing and trivalent chromium passivation.

Features of cyanide-free alkaline zinc: cyanide-free alkaline zinc (zincate galvanizing) has a pH of 14, contains no sodium cyanide, has a current efficiency of around 80%, has excellent metal distribution, has a homogeneous coating, has a small thickness difference, has good deep plating capability, has a relatively high tolerance to impurities, has good corrosion resistance and has better adhesion power than acid zinc, and is mainly used for suspended plating.

Characteristics of the potassium chloride galvanizing process: potassium chloride galvanizing is carried out under weakly acidic conditions, with a pH generally between 4.8 and 6.2. Its most important characteristic is its high current efficiency of around 96% or more and its good brightness, and it is mainly used for barrel plating.

Features of the trivalent chromium passivation process: no hexavalent chromium, easy to wash, complies with environmental requirements; easy to use, uniform color; passivation film has good heat and corrosion resistance; one-component, easy to maintain and manage; neutral salt spray achieves blue and white passivation in 48 hours / color passivation in 96 hours or more.