Surface engineering is to design a composite system of a coating and a substrate together
to give a performance which cannot be achieved by either the coating or the substrate alone.
Coatings can improve the appearance of surfaces; coatings can protect surfaces from adverse
environment; and coatings can enhance many mechanical properties. This is possible by the
application of any of the four main types of coating processes: 1) molten (thermal spraying,
welding); 2) gaseous (vapor deposition, ionized plasma); 3) solution (electroless or electrolytic
plating, resin bonding); 4) solid (friction welding, roll cladding)