5. Considerations on surface finishes

C. Beauvais explains that, from a physical-chemical point of view, surface free energy determines a metal's chemical reactivity towards the outside world, and that this energy is a function of the crystallographic plane parallel to the surface. It also indicates that several types of contamination are to be considered:

• chemical layers ;

• chemical adsorption ;

• physical adsorption ;

and that "as a general rule, surface preparation is carried out to bring the emerging crystals into a receptive condition, with the aim of ridding them of all foreign bodies and chemical compounds covering them, so that the coating forms or is in as intimate contact as possible with the emerging atoms of the crystals" [15]...