under humid conditions. Mineral spirits or acidwashes should definitely not be used at thisstage.2. Etch the surface with a mild phosphoric acidwash. Etching increases paint adhesion andhelps overcome the stress forces generated byexpansion and contraction of the galvanizedcoating. After acid washing the surface, rinse itwith clean water and allow to dry. When usingacid, remember the situation can represent ac-tual or potential danger to yourself and otheremployees in the area. Continuous and auto-matic precautionary measures minimize safetyproblems and improve both efficiency andmorale of the crew.3. Apply a specially formulated primer. Two basictypes of primer are in common use: zinc-boundand cementitious-resin. The zinc-bound type isused for normal exposure. Most types of finishcan be used over this type of primer. Latexemulsion paints provide a satisfactory finish.Oil-based products should not be used over ce-mentitious-resin primers. A minimum of twocoats of finish is recommended over each typeof primer.CONCRETE AND MASONRYIn Navy construction, concrete and masonry arenormally not painted unless painting is required fordamp-proofing. Cleaning concrete and masonryinvolves the removal of dirt, mildew, and efflo-rescence (a white, powdery crystalline deposit thatoften forms on concrete and masonry surfaces).Dirt and FungusDirt and fungus are removed by washing with asolution of trisodium phosphate. The strength of thesolution may vary from 2 to 8 ounces per gallon ofwater, depending upon the amount of dirt or mildewon the surface. Immediately after washing, rinse offall the trisodium phosphate with clear water. If usingoil paint, allow the surface to dry thoroughly beforepainting.EfflorescenceFor efflorescence, first remove as much of thedeposit as possible by dry brushing with a wire brushor a stiff fiber brush. Next, wet the surface thoroughlywith clear water; then, scrub with a stiff brush dippedin a 5-percent solution (by weight) of muriatic acid.Allow the acid solution to remain on the surface about3 minutes before scrubbing, but rinse thoroughly withclear water immediately after scrubbing. Work onsmall areas not larger than 4 square feet. Wear rubbergloves, a rubber apron, and goggles when mixing andapplying the acid solution. In mixing the acid, alwaysadd acid to water. Do not add water to acid; this cancause the mixture to explode. For a very heavydeposit, the acid solution may be increased to 10percent and allowed to remain on the surface for 5minutes before it is scrubbed.Repairing DefectsAll defects in a concrete or masonry surface mustbe repaired before painting. To repair a large crack,cut the crack out to an inverted-V shape and plug itwith grout (a mixture of two or three parts of mortarsand, one part of portland cement, and enough waterto make it putty-like in consistency). After the groutsets, damp cure it by keeping it wet for 48 hours. If oilpaint is to be used, allow at least 90 days forweathering before painting over a grout-filled crack.PLASTER AND WALLBOARDWhenever possible, allow new plaster to age atleast 30 days before painting if oil-based paint is beingapplied. Latex paint can be applied after 48 hours,although a 30-day wait is generally recommended.Before painting, fill all holes and cracks withspackling compound or patching plaster. Cut out thematerial along the crack or hole in an inverted-Vshape. To avoid excessive absorption of water fromthe patching material, wet the edges and bottom of thecrack or hole before applying the material. Fill theopening to within 1/4 inch of the surface and allow thematerial to set partially before bringing the level upflush with the surface. After the material hasthoroughly set (depending on the type of filler used),use fine sandpaper to smooth out the rough spots.Plaster and wallboard should have a sealer or a primecoat applied before painting. When working with oldwork, remove all loose or scaling paint, sand lightly,and wash off all dirt, oil, and stains. Allow the surfaceto dry thoroughly before applying the new finish coat.WOODBefore being painted, a wood surface should beclosely inspected for loose boards, defective lumber,protruding nail heads, and other defects or irregularities.Loose boards should be nailed tight, defective lumbershould be replaced, and all nail heads should be counter-sunk.A dirty wood surfaceby sweeping, dusting, andsoap and water. In washing8-5is cleaned for paintingwashing with solvent orwood, take care to avoid
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