Review of duplex electroless coatings and their properties

Electroless coatings (unary, binary and ternary) are utilised nowadays on a wide scale due to their good tribological and mechanical properties (anti-wear, friction, hardness, anti-corrosion).In recent years, the demand and need has increased to have a coating/finished product which has one or more of these properties. This has resulted in an increased level of research and related publication output on the development of different types of surfaces and coatings with different elements. From this work, the concept of multi-layered/duplex coatings arose. In these coatings, different types of layers are developed which superimpose on each other to provide properties which are better than each individual layers. This paper presents a review on the layers which have been used in various duplex coatings, their electroless bath preparation methods, and how the produce multi-layers influence the final properties.