Electrochemically, alloys can be designed to produce different corrosion potentials than their alloying elements. It is possible, therefore, to maintain the sacrificial protection of zinc coating over steel, but at a different potential, closer to steel, by alloying it with another metal, preferably more noble than zinc. As a result, the alloy corrodes
at a much slower rate than zinc alone, affording better corrosion protection. Some of these alloys have been found to be excellent replacements for cadmium plating in many applications.
Zinc Cobalt Alloy Plating
Conventional plating used for corrosion resistance like Zinc plating, etc., provide only limited increase in life. A modified zinc plating co-deposited with cobalt improves the life more than 300%.
Electrochemically, alloys can be designed to produce different corrosion potential than their alloying elements. It is possible, therefore to maintain the sacrificial protection of zinc coating over steel, but at a different potential closer to steel, by alloying it with another metal, preferably more noble than zinc. As a result the alloy corrodes at a much slower rate than zinc alone, affording better corrosion protection.
Zinc generally comprises 85-99 percent of the alloy. Japan and many European countries effectively banned cadmium plating during the 1970s. Due to the toxicity associated with cadmium and cyanide (an ingredient in most cadmium plating solutions), Zinc Cobalt alloys have been found to be excellent replacements for cadmium plating in many applications.
Zinc – Iron plating
Zinc-Iron plating is a high performance coating. Compared to pure zinc plating, this process provides superior sacrificial protection to steel, since it corrodes much more slowly than pure zinc. The degree of protection and rate of corrosion depends on the alloy metal and composition. The demand for higher quality, longer lasting, more corrosion resistant coatings in industries particularly, automotive has played a large role in the development and use of Zinc-Iron coatings.
