Surfaces are primarily roughened to achieve a surface enlargement which improves the adhesion of subsequently applied coat and adhesives. During the roughening process, surface layers acting as a separating layer are also removed.
Traditionally, surface roughening is an application for mechanical machining processes, in particular grinding or sandblasting. With mechanical roughening processes it can be problematic to remove grinding residues (grinding dust) completely, which in turn worsens the adhesion of coatings. Surfaces can be roughened in low-pressure plasma by plasma etching. Micro-sandblasting by ion bombardment in the argon (Ar) plasma is a particularly effective method. It is also referred to as ionic or physical etching, because chemical reactions do not play a role in the process. Micro-sandblasting acts on almost all surfaces (non-selective) and is strongly anisotropic. As as the case for mechanical roughening, micro-sandblasting also removes contaminations. Though the usual roughening depth with micro-sandblasting via physical etching is below 1 µm, comparable or more pronounced surface enlargements are achieved as with the mechanical process.