SUPPORT EQUIPMENT (SE) CORROSION REMOVAL AND SURFACE PREPARATION The following text discusses surface preparation as well as mechanical and chemical paint and corrosion removal methods for SE. They are listed in order from the most effective or preferred to the least effective and not preferred. Each SE maintenance station develops the procedures for operating surface preparation equipment according to the applicable MIMs. The key to achieving a successful, long-lasting coating system lies in good bonding between coating and metallic surfaces of SE. Paint will not bond to a surface that is poorly prepared. Dirt, oil, grease, corrosion by-products, moisture, and other contaminants prevent complete contact between paint and base metal. In addition, a metallic surface must be roughened to enable the paint system to bond to the surface. This roughened or anchor pattern can be produced by mechanical means or by chemical etchings. You should remove corrosion, scale, and old paint from SE by the least destructive method. Where simple touch-up painting is required. feather the edges of existing sound paint with light sanding to provide an anchor for the touch-up paint. You must apply the initial paint to SE as soon as possible following surface preparation. A prolonged lapse in time between surface preparation and painting allows corrosion to form on the prepared surface. This corrosion will cause later coating system failure. REMOVING DIRT, OIL, AND GREASE The first step in surface preparation is the removal of dirt, salt, lubricants. hydraulic oil, and other surface contaminants from SE. When grease and oil are present during abrasive blasting, grinding, or wire brushing, they will spread out over the treated surface and disrupt the coating bond. The cleaning method that you use depends on the type of soil, its extent, and the available cleaning equipment. Detergent cleaning, solvent cleaning, emulsifiable solvent cleaning, and acid cleaning are cleaning or degreasing methods. Detergents and solvents are highly effective in attacking and dissolving grease and oil on metal surfaces of SE. Most solvents can be either applied by vapor degreasing equipment or by wiping. Solvents are specially useful for cleaning small parts and spot-cleaning jobs. Disadvantages of degreasers lie in their toxicity and flammability. Many solvents are particularly dangerous when used on oxygen service equipment. Emulsifiable solvent (solvents suspended in a gelatinlike medium) cleaning is an effective cleaning method for removing heavy oil, grease, wax, and other contaminants of SE. Acid cleaning combines the forces of oil solvents and detergent cleaners in removing grease, oil, light rust, and other contaminants. The method is useful on the heavy steel structures of SE where surface etching is required. This cleaning method requires a thorough rinse with clean water. MECHANICAL CORROSION REMOVAL ON SUPPORT EQUIPMENT (SE) Abrasive or grit blasting is the preferred surface preparation method for many of the components of SE. Such blasting provides the clean anchor pattern needed by most coating systems. Wet abrasive blasting is preferred to dry blasting. Before blasting, disassemble the components according to the applicable technical manual. Mask all areas that should not be blasted, such as tapped holes, key ways, machined surfaces, reflectors, lights, and gauges. When using abrasive blasting equipment, you must wear protective clothing, face shield or safety goggles, and a respirator. Wet Abrasive Blasting Water blasting is a technique that requires high-pressure producing equipment. It involves the propelling of water and blasting beads. The water blast method removes surface chemical contaminants, deteriorated paint, grease accumulations, oil, and mastic materials from SE. NOTE: You must use Sodium Nitrite MIL-S-24521 during the abrasive process to prevent flash rusting. The Hydroblaster or other water blast machines can be dangerous if not handled properly or with sufficient safeguards. 4-42