The effect of VpCI chemical pre-treatment on adhesion of organic coatings

摘要

Surface preparation is the first step in a coating protection process and the most critical factor affecting the total success of surface treatment. The presence of even small amounts of surface contaminants such as oil, grease and salts can reduce coating adhesion to the substrate. Abrasive blasting is the most often used method for surface pre-treatment before coating. It is a very efficient method, creating uniform surface roughness and cleanliness. But, chemical contaminants that are not readily visible, such as chlorides and sulphates often remain on the surface resulting in premature failure of the organic coating. To overcome that and to provide the best possible contact surface for the applied coating, very often chemical cleaners are used. Today, because of environmental concerns, chemical cleaners for surface preparation are water based products containing a corrosion inhibitor for flash rust prevention after cleaning. In this paper the influence of three waterborne VpCI chemical cleaners on the adhesion of organic coatings were studied. The mild steel samples were prepared with and without chemical cleaners containing a vapor phase corrosion inhibitor. The study was conducted in a salt spray chamber and humidity condensation chamber, whereas the adhesion was tested before and after accelerated exposure to a corrosive environment. The coating resistance was studied in 3.5% NaCl solution by electrochemical impedance spectroscopy. The results showed that an appropriate water based cleaner could replace solvent based thinner in the surface preparation process after abrasive blasting.