As is the case with most processes, the surface coating (liquid painting / powder coating) process also starts with the base preparation – "Surface preparation". This process is the foundation of the coating process and is of utmost importance. The pretreatment process is used to remove the contamination (like oil, grease or rust) from the surface of the articles to be coated and prepare a clean base for best coating results. The pretreatment process is mainly a chemical cleaning process designed according to the chemical composition of the base material and intensity of contaminants and the capacity of the various commercially available chemicals to act on the same.

Pretreatment process can be classified into two engineering types – Dip type and Spray type. The selection between these two types is based on the article geometry, article weight, volume of production and investment, the chemical process remaining the same for both types.