Electrogalvanizing

Zinc is an essential element of life, naturally present in water, air and the earth's crust. As it can be recycled indefinitely, it contributes to sustainable development, giving it a special place among other metals.

Recommended for iron protection due to its sacrificial properties, since the mid-1970s zinc has become the No. 1 corrosion protection for mild and low-alloy steels. By prolonging their service life, zinc not only helps to protect investments, but also iron ore and energy resources.

In the case of manufactured products, this protection takes the form of a zinc coating of varying thickness (from a few micrometers to a hundred micrometers), depending on the industrial sector concerned and the manufacturing process used [1] :

• hot-dip galvanizing: immersion in a molten zinc bath ;

• matoplasty: development using an impact medium in a chemical environment;

• metallization: spraying molten zinc with a spray gun ;

• sputtering: formation of a zinc deposit, under reduced pressure, from the condensation of a metal vapor from a solid source (target) ;

• zinc flake coating: application of a wet film of organometallic solution containing zinc (and aluminum) flakes, followed by "baking";

• shérardisation: thermochemical process for surface diffusion of zinc into steel;

• electro-galvanizing or zinc electroplating.

Electrolytic zinc plating, the subject of this dossier, is an easy-to-use and economically competitive process. It is achieved by electrolysis of an aqueous solution containing metallic (Zn ^II , Na ⁺ ...) and non-metallic salts, the nature of which depends on the intended application and the desired properties of the coating. The wide variety of deposit characteristics obtained, depending on the formulation and deposition conditions, makes this anti-corrosion coating indispensable in a wide range of applications: sheet metal for the automotive and household appliance industries, from M3 screws to supermarket carts...

In addition to the electrolyte, this treatment requires a manufacturing process, the choice of which depends on the type of product being treated. Three main families of applications are proposed, namely :

• Bulk processing (known as "barrel processing") for small and medium-sized...