What is the core principle of electrogalvanizing?
Electrolysis is used to deposit zinc ions from the plating solution onto the metal substrate, forming a uniform zinc layer for corrosion protection.
What are the commonly used electrogalvanizing processes?
Acidic zinc plating (such as sulfate zinc plating): Fast deposition rate, suitable for simple parts.
Alkaline zinc plating (such as cyanide and cyanide-free alkaline zinc plating): Produces a uniform coating, suitable for complex parts.
Chloride zinc plating: Balances speed and uniformity, making it widely used.
What are the key steps in substrate pretreatment?
Degreasing (chemical/electrochemical), rust removal (pickling), and activation (weak pickling) are required to ensure the substrate is free of oil and scale, which would otherwise affect the adhesion of the coating.
What are the main components and functions of the plating solution?
Main salts (such as zinc chloride and zinc sulfate): Provide zinc ions, serving as the source of the coating.
Cluling agents (such as cyanide and nitrilotriacetic acid): Stabilize zinc ions and prevent precipitation. Additives (brighteners, sizing agents): Improve the brightness and uniformity of the coating.
How does current density affect the coating?
Too low a current density results in a thin and uneven coating; too high a current density can easily cause "burning" (rough, blackened coating). The optimal range must be adjusted based on the process.