The Zinc Electrolytic Iron process consists in the deposition of a metallic zinc alloy with an iron content of between 0.3 and 0.6% by means of the passage of current within a specific electrolyte. In this way, uniform deposits with greater corrosion resistance are obtained than conventional zinc coatings.
The purpose of Zn coatings and their alloys is the corrosion protection of the material that is coated. This is achieved through two mechanisms:
1.- Physical barrier isolating the coated material against the oxidizing medium.
2.- Cathodic protection, with which the deposited layer of Zn acts as a sacrificial metal against the coated material, protecting it. This property is one of the main advantages of Zn coatings and their alloys over other types of coatings.
Among the advantages of the Zn coating and its electrodeposited alloys, compared to other coatings, the low thickness necessary to obtain good corrosion protection (usually working in the range of 8 to 20 microns) stands out, the excellent adhesion with the base metal to be coated, the protective capacity against sacrificial corrosion and the good reactivity for the application of passivation layers and subsequent seals.
The treatments of electrolytic ZnFe are applied both in static, by means of racks where the pieces are covered unitarily, or in drums, where the treatment is in mass. For each piece the appropriate treatment method must be applied depending on its size, geometry, etc.
Passivations that are conversion coatings can be applied to the ZnFe tank by using CrVI salts to protect the tank against corrosion. These passivations are those that confer the colour to the finish, being able to be transparent or black.
By applying seals in the final phase of the process, it is possible to increase the corrosion resistance both to white corrosion (coating corrosion), and to red corrosion (steel corrosion), as well as to parameterize the friction coefficient according to the specification requested.