Journal of Adhesion Science and Technology, Vol.18, No.14, 1643-1661, 2004
Analysis of adhesion in an aggressive environment of a protective paint coating on an aluminium alloy surface treated by air cold plasma
2024 aluminium alloy is commonly used for the fuselage of aircraft or helicopters because of its high strength. The fuselage bears the weight of the movers of the aircraft and the oil or petrol tanks. It works where the climatic conditions are very harsh. i.e. very low temperature and salt fog, and in presence of aggressive chemical agents. The aluminium fuselage needs to be protected from water, heat and aggressive chemical agents, such as hydrocarbons, lubricating oils or salt fog, by a paint coating. It is important that the adhesion between the paint and the aluminium alloy remains strong for a long time. A complex and critical process is industrially used to enhance both wettability and adhesion of paint to the aluminium alloy. Cold plasma represents an efficient. non-polluting and economical alternative to clean and activate aluminium surfaces. The present work describes the possibility to use an aluminium alloy, pre-treated by cold plasma and then protected by a paint coating, in the presence of water or high temperature, as well as aggressive environmental conditions. Adhesion between the paint and the aluminium surface was characterized by a set of mechanical and physical-chemical tests. Many experimental tests were carried out in order to understand the interaction between plasma and workpiece material. The results obtained by the cold plasma treatment and the commonly used industrial process have been compared. Also. the nature of the relationship between wettability and adhesion was investigated. The results show that cold plasma allows to eliminate cleaning by a solvent and to reduce the quantity of Alodine 1200(R) or XPD(R) primer applied and, therefore, to reduce the use of polluting substances and the weight of the whole helicopter or aircraft.