Surface preparation is the essential first stage treatment of a substrate before the application of any coating. The performance of a coating is significantly influenced by its ability to adhere properly to the substrate material. It is generally well established that correct surface preparation is the most important factor affecting the total success of surface treatment. The presence of small amounts of surface contaminants, oil, grease, oxides and etc can physically impair and reduce coating adhesion to the substrate. Due to the reduction of obtrusive active ions such as chlorides and sulfates, strong bonds are produced between paint and surface.
Adhesion is one of the determinants of coating performance on the surface. It is clear that if there is no adhesion between coating and the surface, the coating is placed on the surface like a plastic layer which is easily removed from the surface with any physical or chemical agent. If the coating is firmly bonded to the surface, it can act as a permanent shield.
The best method for preparing and creating profiles at the metal surface is the blasting method which the surface of metal is thoroughly cleaned by spraying of hard particles such as copper slag, ceramic shot/grit and etc. The standard grades of cleanliness for abrasive blast cleaning are:
Sa 1 Light blast cleaning.
Sa 2 Thorough blast cleaning.
Sa 2 ½ Very thorough blast cleaning.
Sa 3 Blast cleaning to visually clean steel.
Generally, the standard grade of cleanliness Sa 2 ½ is accepted as a minimum of cleanliness.