coating material MIL-M-3171 until you obtain a greenish-brown or brass-colored yellow color. For a proper conversion coating, keep the surface wet with the specified solution until you obtain the desired color. Rinse with fresh water. Remove any excess conversion coating solution that collects into pools within the aircraft. Some magnesium parts in later model aircraft were originally protected by a proprietary (held under patent) electrolytic process. One process is identified by the brown to mottled gray appearance of the unpainted surface. Another process will appear as a green to grayish-green color. These coatings are thicker than those applied by the immersion or brush method, such as MIL-M-3171. The electrolytic finish cannot be restored in the field. Therefore, when failure of the coating occurs, you should remove corrosion and touch up the bare magnesium with MIL-M-3171 chemical treatment solution. You should minimize removal of the electrolytic coatings, as they afford greater protection than the replacement coatings. Q75. What is the purpose for chemically treating a surface for painting? Q76. When failure of the coating occurs, you should remove corrosion and touch up the bare magnesium with what chemical treatment solution? AIRCRAFT PAINTING AND COMPONENT TOUCH-UP LEARNING OBJECTIVE: Identify the materials used and procedures for painting aircraft. The amount of paint touch-up done at organizational- and intermediate-level maintenance varies widely. The amount depends upon the activity involved, the availability of facilities, and the area of operations. The primary objective of any paint finish is the protection of the exposed surface against decay. There are secondary reasons for particular paint schemes. Glare is reduced by nonspecular (not mirrorlike) coatings. White or light-colored, high-gloss finishes reduce heat absorption. Camouflage, high visibility, or special identification marking requirements are met by various paint schemes. REPAINTING SHOULD NOT BE DONE FOR APPEARANCE SAKE ONLY. A faded or stained but well-bonded paint finish is better than a fresh touch-up treatment applied over dirt, corrosion products, or other contaminants. Complete refinishing (particularly under field conditions) should be restricted to those areas where existing paint finishes have degraded until they fail to perform their protective function. However, the organizational and intermediate levels of maintenance should evaluate maintenance and repair of paint finishes. This should be done at the time of aircraft receipt and through constant surveillance and maintenance of finishes during an aircraft’s service tour. Maintenance also should make final recommendations for refinishing an aircraft when the aircraft is scheduled for standard depot-level maintenance (SDLM). General safety precautions should be followed when you paint and when you use special types of paints. These precautions include the following: No eating, drinking, or smoking is allowed in areas where paint or solvent is being used. Prolonged breathing of vapors from organic solvent is dangerous. Prolonged skin contact with organic solvents or materials containing organic solvents can have a toxic effect on the affected skin area. PAINT REMOVAL Paint removal operations at the organizational and intermediate levels of maintenance are usually confined to small areas, or possibly a whole panel. In all cases, the procedures outlined in the MIM that applies should be observed. General stripping procedures are contained in NAVAIR 01-1A-509. Materials All paint removers are toxic and caustic; therefore, both personnel and material safety precautions must be observed in their use. Personnel should wear eye protection, gloves, and a rubber apron. Paint remover, specification MIL-R-81294, is an epoxy paint remover for use in the field. This remover will strip acrylic and epoxy finishes. Acrylic windows, plastic surfaces, and rubber products are damaged by this material. This material should not be stocked in large quantities as it ages rapidly, degrading the results of stripping action. This paint remover must NOT be used to remove paint from composite materials. 4-46