I am preparing to post soon after completion my case i am going to paint shortly. Since i have been looking for tips on painting plastic since ive never sprayed it but ive sprayed alum., i ran accross this and i thought it might interest some of you.
SURFACE PREPARATION GUIDE
The quality of surface preparation, and surface repair on new, or repaint surfaces, significantly affects the amount of preparatory work that will be required for all subsequent repaints. Surface preparation and surface repair are the most important requirements for maximum durability from any paint system. Because the results of surface preparation and repair are quickly concealed by the first coat of paint, the effects are not usually evident until premature paint failure occurs.
The first step should always be a thorough examination of the surface to be painted, checking for peeling and faded paint, dirt, chalking, grease, cracking, knots, bare areas, mildew, rust, nail stains and structural problems. All surfaces, whether painted or unpainted, must be clean, free from shine, sound and dry prior to finishing.
GENERAL SURFACE PREPARATION
LOOSE AND PEELING PAINT
Remove as much loose and peeling paint by scraping, wirebrush or power-washing the surface.
Feather-sand rough edges smooth until they blend with bare surface.
DIRT, GREASE, OIL,CHALK AND UNDER-EAVE DEPOSITS
Remove these deposits by washing with a detergent solution (TSP) or commercial cleaner recommended for cleaning painted surfaces using a sponge or brush. Protected areas, such as under eaves and overhangs, need special attention to remove invisible deposits that can promote a premature peeling problem. After washing, thoroughly rinse with clean water and allow to dry. Power-washing is also a fast, effective method of removing dirt, chalk, etc. If a power-washer is used, follow the manufacturer's recommendations and warnings.
Spotty patches that look like dirt, but do not come off when scrubbed with detergent solution, are probably mildew. Mildew can occur on any side of the house, but is more likely to grow in shaded areas or behind shrubbery. It can easily be identified from other forms of discoloration by applying a few drops of bleach. If mildew is present, the black, gray or brown color will bleach out and disappear within one or two minutes. Mildew must be killed and removed before repainting. If the mildew is not completely removed, the active spores will continue to grow and may almost immediately begin to reappear on a recently repainted surface. Where mildew is present, apply a solution of one part household bleach and three parts water, or use a commercial mildew remover. It is mandatory to wear rubber gloves, goggles, long-sleeved shirt and long pants to protect eyes and skin when using a mildew remover. In addition, protect grass, trees and shrubs with plastic covers. CAUTION!! DO NOT MIX BLEACH WITH AMMONIA OR DETERGENTS CONTAINING AMMONIA. Follow specific instructions if a commercial mildew remover is used.
Remove all rust by sandblasting, wirebrush, steel wool, sandpaper or naval jelly (rinse thoroughly). See Iron, Steel and Ferrous Metal section for SSPC preparation methods.
CRACKS, SPLITS AND OPEN JOINTS
Cracks, or open joints, where water may enter should be caulked with a high-quality, paintable acrylic caulk. Apply primer over caulked area.
Always dull surfaces with sandpaper or liquid de-glosser. CAUTION - liquid de-glossers are generally not recommended on surfaces to be painted with water-based paints.
Replace loose nails with slightly larger, galvanized nails. Leave nail heads flush with hardboard surfaces and counter sink on all other wood surfaces. Prime with a corrosion resistant primer.
This condition can be encountered on hardboard surfaces. If a stain or discoloration persists after removing dirt and/or mildew, it may be a wax migration from the siding. It can be identified by applying a few drops of water, both to a discolored area and an adjacent non-discolored area. If the water beads on the discolored area, but spreads or is absorbed in the areas around the stain, a wax migration condition probably exists in the stained area. In most cases this discoloration can be removed with a hot detergent solution (TSP), followed with a thorough rinsing with clean water. In extreme cases removing the stain by wiping the area with a clean rag, wet with mineral spirits, may be necessary, followed by a detergent solution (TSP) wash and clean-water rinse. Repeating either process may be necessary until clear water ceases to bead up on the affected area. Prime the affected area prior to topcoating.
PREVIOUSLY COATED SURFACES
Maintenance painting will frequently not permit complete removal of all old coatings prior to repainting a particular surface. Recognize that any surface preparation, short of removal of all old coatings, may compromise the service life of the new coating system. Check compatibility of previously painted surfaces using a test patch with the coating if there is any doubt on recoatability.
NEW ALUMINUM & GALVANIZED SURFACES
To paint these surfaces, you must start by solvent cleaning (with mineral spirits) to remove any oily residue. Prime with either a good quality latex or oil primer formulated for these surfaces.
(Exposed to the elements for at lease 2 months.) If this is possible, all that is necessary is to wipe it clean from dirt & prime with oil or latex primer.
Shall be cleaned free of dirt, oxides and foreign matter. Acid etching with muriatic acid may be required to remove oxidation. Prime with an oil based product.
BRASS & BRONZE
Remove only loose tarnish, but not all tarnish needs to be removed. Then wash with detergent to get rid of dirt and grease. Rinse well and allow to dry. Prime with a top quality oil metal primer.
Start by roughing up the surface with fine sandpaper or emery cloth. Wash with soap and water, then rinse and allow to dry. Prime with oil-based metal primer
IRON, STEEL, & FERROUS METAL
NEW: Wipe clean with mineral spirits to eliminate any oil or grease. Remove all rust and mill scale. Prime with a good oil-based metal primer
IRON AND STEEL: If the old film is in good sound condition, all that needs to be done is to de-gloss the old surface with light sanding and clean with mineral spirits. If the old film is in poor condition, it should be removed with paint remover. If metal has rusted, that too must be removed. Prime all bare spots with oil-based metal primer
Abrasive Blast Cleaning:
WHITE METAL BLAST CLEANING (SSPC-SP5, NACE No. 1)
A surface with a gray-white, uniform metallic color, slightly roughened to form a suitable anchor pattern for coatings. This surface is free of all oil, grease, dirt, mill scale, rust, corrosion products, oxides, paint and other foreign matter.
NEAR-WHITE BLAST CLEANING (SSPC-SP10, NACE No. 2)
A surface from which all oil, grease, dirt, mill scale, rust corrosion products, oxides, paint or other foreign matter have been removed except for light shadows, streaks or other discolorations (of oxide bonded to metal). At least 95% of any given square inch has the appearance of "White Metal," and the remainder is limited to slight discolorations.
COMMERCIAL BLAST CLEANING (SSPC-SP6, NACE No. 3)
A surface from which all oil, grease, dirt, rust scale and foreign matter have been removed except for slight shadows, streaks or discoloration caused by rust stain or mill scale oxide binder. At least two-thirds of any square inch shall be free of all visible residues and the remainder shall be limited to light discoloration, slight staining, or light residues mentioned above. If the surface is pitted, slight residues of rust or paint are found in the bottoms of the pits.
BRUSH-OFF BLAST CLEANING (SSPC-SP7, NACE No. 4)
A surface from which oil, grease, dirt, loose rust scale, loose mill scale and loose paint are removed, but tightly adhering mill scale, rust, paint and coatings are permitted to remain if they have been exposed to the abrasive blast pattern, so that numerous flecks of the underlying metal are uniformly distributed over the entire surface.
WATER BLASTING (NACE No. RP-01-72)
Removal of oil, grease, dirt, loose rust, loose mill scale and loose paint by water at pressures of 2000-5000 psi at a flow of 4-14 gallons per minute.
Hand and Power Tool Cleaning:
HAND TOOL CLEANING (SSPC-SP2)
POWER TOOL CLEANING (SSPC-SP3)
These specifications describe methods of preparing metal surfaces by removing loose mill scale, loose rust and loose paint by wire-brushing, sanding, scraping or chipping with hand or power tools.
Other specifications sometimes used for surface preparation are SSPC-SP1, SOLVENT CLEANING, which describes methods of removing oil, grease, dirt and certain chemical compounds by solvent washing or vapor de-greasing, and SSPC-SP8, PICKLING, which describes removal of mill scale and rust by chemical reaction. High-pressure water blasting is an effective means of removing old paint and rust scale. Abrasive injection or dry blasting must be used to achieve an anchor patte
Wash to remove grease with a detergent solution. Sand lightly to etch the surface. Prime with epoxy metal primer.
NEW OR UNPAINTED CONCRETE FLOORS
Floors - Check for any dampness on floors by placing a rubber mat down and leaving overnight. Upon inspection, if dampness occurs on the back side of the mat, or concrete surface has been darkened by moisture - Do Not Paint. New concrete should be allowed to cure 30 days at 75Â° F. prior to painting.
All concrete surfaces should be etched before painting with a solution of one part muriatic acid and two parts water. (Wear rubber gloves and goggles because this solution is hazardous.) Allow solution to bubble, then rinse well with clean water. Brush while rinsing to remove all loose concrete. Allow surface to dry completely. Additional vacuuming may be required to remove powdery residue left from etching. Concrete can also be prepared for painting by lightly sandblasting.
Your first coat of paint should be a thinned-down version of your finish. Thin one pint water per gallon of latex paints. Thin one pint mineral spirits per gallon of solvent-based paints. The topcoat should be used straight out of the can.
PAINTED CONCRETE OR WOOD FLOORING
Be sure surface is free from dirt, dust, etc. by sweeping or vacuum cleaning. Remove grease, oil, floor compound and wax by chemical cleaning. Scrape carefully to remove deteriorated coatings. If remaining coating is glossy or very hard, sand it lightly for good adhesion of subsequent coatings. The surface must be thoroughly dry before coating.
MASONRY (BLOCK, CINDER, AND CONCRETE)
Allow to dry 30 days under normal drying conditions prior to painting. If efflorescence or cement dust is present on masonry and concrete, it should be removed by etching with a 10% solution of muriatic acid. Flush off surface, after etching, with clean water and allow to dry. If etching is not possible to neutralize efflorescence; sand, scrape and wire brush; then coat with masonry conditioner before painting. Surfaces should also be free of all dust, dirt and loose or excess mortar. Porous surfaces should be filled with block filler before painting. Latex finishes will afford best results. No special primer is required.
UNPAINTED STUCCO AND BRICK
This needs no special preparation. However, stucco should be allowed to sit and dry thoroughly before it is painted. If surface is soft or slightly powdery, first apply one coat of masonry conditioner.
Apply two coats of exterior latex paint formulated for masonry.
Should be cleaned and free from loose paint and all holes should be patched. Paint with exterior latex.
CERAMIC TILE AND GLAZED BRICK
Wash with detergent, then go over with a paste of powdered pumice and water to roughen surface. Paint with a good quality 2-part epoxy paint.
UNPAINTED EXTERIOR WOOD SURFACES
Should be clean and dry. Prime and paint as soon as possible. No painting should be done immediately after a rain or during foggy weather, or when the temperature is below 50Â° F. Knots and pitch streaks shall be scraped or burned, sanded and spot primed before receiving a full coat of primer. All nail holes or small openings should be filled after the priming coat is applied.
Prime with a high quality oil or latex primer. (See cedar and redwood.)
CEDAR OR REDWOOD
The main problem with painting these surfaces is the fact that it discolors. This is known as tannin bleed. To control bleed follow these recommendations: Priming with an alkyd-based primer will afford better stain blocking characteristics than a latex primer. In wood containing an extremely high amount of tannin, two coats of primer may be necessary.
Before finish is applied to the panels, they must be cleaned. Apply an alkyd or latex primer, even if hardboard is pre-primed, then finish with desired topcoat.
If glazed, allow at least two years before painting. If shingles are porous, treat with masonry conditioner. If shingles are weathered, remove all dirt and dust. Prime with latex primer.
Shall be allowed to dry thoroughly for at least 30 days before painting. Bare plaster should be dry, cured and hard. Fill any holes and cracks. Sand smooth. Paint with latex paint. Primer may be used if desired. If so, use a latex type. If previously coated with a cement-based coating or lime wash, treat first with masonry conditioner.
Prime with a latex primer-sealer. Do not use a solvent based primer since it will raise the fiber of the wallboard.
Should be well cleaned before painting. Finish with flat wall or ceiling latex to retain acoustics.
Spraying is the best way to paint these surfaces, but brush and roll-on methods may also be used.
If it has a shiny surface, dull by sanding lightly and clean with mineral spirits to remove any wax. Prime with oil primer.
WOODWORK - INTERIOR
All finishing lumber and flooring should be sanded smooth, with the grain -not across it. Surface blemishes shall be corrected. If painting use an oil-based enamel undercoater for priming.
Remove loose paper. Test for bleed by applying latex to a small area to make sure wallpaper is waterfast. If bleed occurs, seal paper with one coat of white shellac reduced with an equal volume of alcohol. Avoid skips when applying shellac. Allow to dry one hour before topcoating.
De-gloss or etch the surface by lightly sanding. Apply epoxy polyamide or acrylic urethane topcoat for surfaces that may be abused. Light surface area may only require an alkyd topcoat.
Wash and allow to air dry. Apply either an epoxy or alkyd enamel.
If it is flexible, Do not paint it. If stiff, wash with detergent and roughen with sandpaper or steel wool. Prime with solvent-based primer.
Scrub with detergent and sand lightly with sandpaper. Prime with alkyd-base primer and finish.