*3.1.1. Substrate and substrate preparation*

The main idea of coating processes is to protect the main material, to be specific, substrate, from environmental conditions, and to improve its mechanical properties. Undoubtedly, the perfect choice for such engineering applications is steel due to its unique properties. Even though this material group has a lot of advantages, the surface of the steel substrate has to be protected by several coating techniques. Electrical conductivity of steel substrates allows them to be coated by electrolytic deposition techniques, including electro codeposition. The quality of the substrate should be chosen according to the application and is the important detail; it should be coherent with the coating material properties-side (such as hardness and modulus of elasticity).

The preparation of the substrate before plating is another point to be taken into consideration. The coatings with perfect properties have no meaning without a good adhesion. Adhesion between the coating and the substrate identifies the coating quality and determines the life time of this structure. The preparation generally includes chemical and/or mechanical cleaning steps to remove contaminants from its surface [8].
