Zinc-nickel alloy electroplating is also one of the most commonly used surface treatment methods in the fastener industry.
Principle:
The principle of zinc-nickel electroplating is the same as that of zinc electroplating discussed in previous articles, as both belong to the category of electroplating. This process utilizes electrolysis to form a uniform, dense, and well-adhered metal or alloy deposition layer on the product surface.
Among zinc-based alloys, the zinc-nickel alloy coating is a new and excellent protective layer, suitable for use in harsh industrial atmospheres and severe marine environments.
The corrosion resistance of a zinc-nickel alloy coating with 7–9% nickel content is more than three times that of a zinc coating, while a zinc-nickel alloy coating with approximately 13% nickel content offers more than five times the corrosion resistance of a zinc coating, representing the highest level of corrosion resistance. (For fastener zinc-nickel electroplating, a zinc-nickel alloy layer with 12%–15% nickel content is typically used.)
Due to its outstanding characteristics such as high corrosion resistance, low hydrogen embrittlement, weldability, and machinability, zinc-nickel alloy has long attracted significant attention, and its applications are becoming increasingly widespread.
Classification:
Zinc-nickel alloy plating solutions are mainly divided into two types:
Weakly acidic systems: These solutions have simple compositions, high cathode current efficiency (generally above 95%), stable plating baths, and are easy to operate.
Alkaline zincate solutions: Their main advantages include excellent throwing power, uniform alloy composition and coating thickness across a wide current density range, minimal corrosion to equipment and workpieces, ease of operation, process stability, and lower costs.
Color and Salt Spray Test Duration:
The table below outlines the specifications for zinc-nickel alloy colors and the corresponding salt spray test durations as per the international standard ISO 15726:
The table below shows the salt spray test requirements for zinc-nickel alloy coatings as per the Volkswagen standard VW 13750:
The table below presents the salt spray test requirements for zinc-nickel alloy coatings as per the General Motors standard GMW 4700:
