When two different metals come in contact with each other in presence of an electrolyte (e.g. water), they form a galvanic cell in which the lesser noble metal (e.g. Zn) corrodes in favour of the more noble metal (e.g. steel). This electrochemical reaction is the base for the complex field that is cathodic protection.
Galvanic, cathodic protection, or active protection, arises from zinc (the anode) sacrificing itself in favour of the base metal -steel (the cathode) with the resulting flow of electrons preventing steel corrosion. In this way the protection of the metal is guaranteed, even when the zinc layer is slightly damaged.
Other well-established methods of cathodic protection include hot-dip galvanising (HDG) and zinc thermal spraying, both of which exhibit a constant sacrificial rate of the zinc layer.
With ZINGA the sacrificial rate reduces dramatically after the zinc layer has oxidised and the natural porosity has been filled with zinc salts. Additionally the zinc particles within the ZINGA layer are protected by the organic binder without adversely affecting the electrical conductivity. This enables ZINGA to create nearly the same galvanic potential between the zinc and the steel as hot dip galvanising but with a lower rate of zinc loss because, put simply, the binder acts as a “corrosion inhibitor” to the zinc.
Passive protection, as provided by paints and cladding, creates a “barrier” between the steel substrate and the elements. Once this barrier is compromised, the moisture and atmospheric salts will be able to start corroding the steel beneath the damaged area. This corrosion will then begin to creep extensively beneath the coating.
With ZINGA, the organic binder and the zinc oxide layer that forms on the surface create an impervious barrier by blocking the zinc’s natural porosity with oxide particles. Unlike other passive coatings, once breached, the zinc oxide layer simply renews itself by re-oxidising. This layer of oxides is the reason behind the matt appearance of ZINGA as opposed to the shiny hot-dipped finish.