CHAPTER 2 UNDERCOATS, FINISH MATERIALS, AND RELATED PRODUCTS

TM 43-0139 CHAPTER 2 UNDERCOATS, FINISH MATERIALS, AND RELATED PRODUCTS Section I. GENERAL WARNING Before beginning any painting related activity, read Chapter 1, Section II, Safety Summary. 2-1. APPLICATION This chapter is intended to serve as a general guide to the selection of suitable materials, procedures, and systems for painting and otherwise finishing metal and wood surfaces. If the correct finish system (see Chapter 3) is used and properly applied, it will keep maintenance to a minimum. Otherwise, moisture or other substances will penetrate the coating and cause the metal to corrode or the wood to rot. Usually the finish coat alone will not provide sufficient protection. For example, lusterless olive-drab enamel, which is somewhat porous, offers relatively little protection; its main function is camouflage. The required protection is provided mainly by primers that, for metal, contain rust-inhibiting pigments, and for wood, have high moisture resistant qualities. 2-2. FINISH SYSTEMS a. Protective coatings are applied to metal and wood surfaces to protect them from the destructive action of moisture and other injurious agents. In addition, colored coatings improve the appearance of the surfaces to which they are applied and serve to denote the military organization to which the item being painted belongs. Coatings must also resist weathering, cleaning, fumes, oil, the action of fungi, and other causes that impair their protective qualities. b. Because no single finish material can fulfill all of the requirements mentioned above, finishes, as applied to both metal and wood, are usually composed of two or more materials, each of which serve a definite purpose in the combination coating known as a "finish system." Detailed information on finish systems may be found in chapter 3 and in MIL-STD-171, MIL-STD-709, MIL-T-704, MIL-STD-193, MIL-STD-194, and MIL-F-14072. 2-3. FINISH SYSTEM MATERIALS a. Fillers. Fillers are heavy-body materials, usually in paste form, that are used to fill depressions and holes and provide a smooth surface after sanding. b. Primers. Primers are used on metals to provide a corrosion-resistant coating to which the subsequent finish coat will firmly adhere. c. Sealers. Sealers are used to fill or seal the pores of wood and prevent the contamination of a finish coat by the "bleeding" of an underlying stain or colored filling material. Certain sealers also contain fungicides. d. Thinners. Tinners make paint workable by adjusting the paint or coating consistency for easy application. e. Topcoat or Finish Coat. This is the final coat in a finish system. It may be enamel, lacquer, paint, or varnish, depending on the service requirements desired. Section II. FILLERS 2-4. GENERAL Fillers, like primers and sealers, are undercoats used to prepare metal or wood surfaces for subsequent and final coats of enamel, lacquer, paint, or varnish. They are heavy-bodied pigment materials, and except for the graduation fillers, are applied with a putty knife, saptula, or other similar tool. They are always used in conjunction with finish coats. 2-1