In surface technology, anodizing refers to a group of coating processes in which oxide layers are produced or reinforced on metallic objects by means of electrolysis. In anodizing, the metal is submerged in an electrolytic solution (e.g. sulfuric acid) and functions as an anode (positive pole). The electric current forms an oxide layer on the component’s surface, which can vary in thickness depending on the strength of the voltage. Anodizing aluminum ist the most widely used process.
To create corrosion protection for ferrous surfaces, black finishing involves submerging workpieces in baths containing acidic or alkaline solutions or molten salts. This process forms an oxide layer of a striking deep black color on the surface, the thickness of which is approximately 1 µm. Due to this small layer thickness, the treatment hardly affects the dimensional accuracy of the workpieces. Thanks to this property and its low thermal load, burnishing is one of the most frequently used processes in machine and tool construction.
Nickel plating is the collective term for various processes for producing a nickel coating on mostly metallic objects. Due to its special properties, nickel is particularly suitable for many coating metal applications. Nickel is resistant to air, water, diluted acids and most alkalis, but not to nitric acid, concentrated hydrochloric acid and ammonia.
Through the process of galvanizing, steel is provided with a thin layer of zinc to protect it from corrosion. As a metallic coating, in addition to its shielding effect, zinc also offers active corrosion protection by acting as a sacrificial anode to the more noble iron (see voltage series). The cathodic effect of the zinc coating prevents the corrosion of the iron up to a distance of about 5 mm, so that defects in the zinc layer and bare cut edges are also protected. However, the resulting bimetallic corrosion accelerates the removal of the adjacent zinc layer.