Preparing enamel or powder coat finishes | List of primers | Cleaning

Preparing enamel or powder coat finishes:
Painting over enamel or powder coat finish outdoor light fixture:
I googled enamel surface preparation for painting; Sanding or steel wool seemed to be the most common recommendation.

Problem is with that they have a textured/bumpy surface so It's difficult to sand or steel wool. Sand blasting would be best in my opinion, but couldn't find that on google. A good primer would be OK. See below.
Another solution is to use a heavy duty Scotch-Brite scouring pad.
Another is to use course a rubbing compound.

I'm of the old school; Surface preparation is key. And oil-based paints are best.
However, oil-based paints have been dumbed down because of VOC (Volatile Organic Compound) regulations and water-based paints have been getting much better.

KILZ and B-I-N are recommended primers.
I checked Home Depot and Lowe's, they both had them but only in white.
B-I-N was only for interior applications.

I am painting over high gloss enamel paint with latex paint - is there any paint that sticks without sanding? - Yahoo! Answers
i am painting over some high gloss enamel paint with latex paint - is there any paint that sticks without sanding all the gloss off the previous surface?

One forum comment says: "Use KILZ Primer and it eliminates the need to sand."
The label on the can says glossy surfaces must be properly prepared.
"On glossy surfaces: scuff sand the surface thoroughly before priming."

You need to get an "etching" primer. There are a few different types, look in your local Do It Yourself store. You can either read the cans or ask an attendant for an "etching" primer, It adheres to anything.
Note: etching primers are for bare metal only.

Adhesion problems to old oil-based enamel surfaces - Paint Forum - GardenWeb
You are never going to get any real serious adhesion until you accomplish two things. One is clean and the other is dull. You have the clean part down but your trim is still shiny. Shiny means slick and paint won't ever stick to slick like it will stick to dull. When you dull a shiny surface, you are giving your primer/paint tooth. Wet sanding doesn't work and I don't believe in deglosser. The reason I don't believe in deglosser is because sanding is easy. You get yourself a few sanding blocks, throw on a dust mask and get after it. Before you know it, it's over and there isn't that much dust made from sanding painted trim. It's a step that really shouldn't be skipped IMO...your problem is evidence of that. The primers that are going to stick the best are bonding primers so be sure you select the right ones. Oil based primer are probably the last primers I would use. BIN would be my first choice and if you don't want to use that then there are a ton of high quality acrylic bonding primers available.

Primers
Note: Most are white only.

  • Zinsser Smart Prime® is a next generation interior/exterior primer that offers the performance of an oil-base primer in an advanced water-base formula. Developed for professional and commercial applications, Smart Prime combines dependable stain blocking power with fast-dry convenience, exceptional flow and leveling and outstanding adhesion to glossy surfaces. It resists rewetting to block water-soluble stains like an oil-base primer and seals oil-soluble stains so projects can be completed with just one primer.
    Label says, "Outstanding adhesion to dense, glossy surfaces; enamel paints and varnishes, paneling, laminates and ceramic tile - without sanding or de-glossing.
    Exterior - New or previously painted wood (pine, fir, cedar, redwood, T-111, plywood, pressure treated wood), hardboard, asbestos shingles, glass, metal (aluminum, stainless steel, galvanized metal), PVC, rigid plastics, aluminum and vinyl siding, fiberglass and masonry (stucco, concrete block, poured concrete and brick)."
    Doesn't cover well according to reviews at Paint Talk
    See Technical Data Sheet
  • Zinsser Cover-Stain®
    interior-exterior oil-base.
    An all-purpose oil-base stain-killing primer-sealer. Ideal for interior and exterior applications. Recoat in only one hour. Great for cedar bleed. May be used under any oil-base or water-base topcoat.
    Sticks to all surfaces without sanding.
    Dries in 1 hr.
  • KILZ has interior and exterior, oil and water based primers that are highly recommended.
  • Zinsser B-I-N shellac-base primer.
    For interior and spot exterior use. Home Depot and Lowes only had the interior version.
  • Bulldog Adhesion Promoter - One sign painter recommended Bulldog. This was designed to help automotive paints adhere to flexible plastic parts (like bumpers).
    One forum post said it made his headlight bezel crack.
  • Prime RX™ Peel Bonding Primer - Sherwin-Williams
    Exterior - water-based.
    PrimeRx Peel Bonding Primer has been engineered to provide strong bonding, bridging and filling capabilities over marginally prepared, peeling and alligatored substrates. Whether it's wood, masonry, stucco, hardboards or chalky surfaces, PrimeRx(TM) penetrates to deliver a tight bond with powerful adhesion, allowing you to achieve great results with less time and effort.
    Goes on milky-white for ease of application and dries clear.
  • DTM Wash Primer Sherwin-Williams
    DTM WASH PRIMER is a low VOC, water based wash primer free of heavy metals and mineral acids. Designed to be applied over aluminum and galvanizing, or used as a tie-coat over zinc rich primers. Accepts high performance "hot" solvent topcoats directly, such as epoxies and urethanes.
  • Self-Etching Primer
    Rust-Oleum® Self Etching Primer prepares bare metal, aluminum and fiberglass surfaces to promote maximum adhesion and smoothness of the top coat. This product is formulated to stop rust and is an essential step to achieve a professionally finished look.
  • POR-15® is a high performance coating designed for application directly on rusted or seasoned metal surfaces. It's a little pricey at $31/pint.

Cleaning outdoor wood (decks, siding, furniture)

There are a number of sources of discoloration of wood decks. These include:
  • dirt and other foreign materials such as tree sap, bird droppings, grease, etc.
  • fungal discolorations with mildew (mold fungi) decay and sapstain growth
  • algae, moss and lichen growth
  • nail and other iron stains
  • tannins and other extractives from the wood
  • graying of the wood due to surface decomposition by sunlight and moisture
  • fading/decomposition of weathered coatings
Biocides/Antimicrobials/Fungicides
  • Sodium hypochlorite: chlorine bleach is good for removing mildew but isn't effective on dirt or other stains. It is more caustic for wood and humans.
    Affects lignin in wood causing degrade if strong.
  • Sodium percarbonate: (OxiCLean) When mixed with water, this chemical forms hydrogen peroxide (an oxygen-based bleach) and sodium carbonate, which acts as a detergent. It is good for removing dirt, mildew.
See Mold/Mildew

Stain Removal:
Oxalic acid will lighten or remove gray stains.
Sodium Hydroxide (Lye, oven cleaner, draino) will remove pink stains.

Deck Cleaners and Restorers..........

Until about ten years ago there were few, if any, products of this type on the market. Most coatings manufacturers recommended that decks and other exposed wood surfaces be cleaned before refinishing. The usual recommended cleaners were household products such as detergents for dirt removal and liquid bleach for mildew removal.

Household cleaners and bleaches can be effective to some extent but they have their limitations. Also, since they are not usually designed for deck cleaning applications they can present some handling problems to do-it-yourselfers and contractors. For example, liquid household bleach should not be mixed or used directly with ammonia or any other detergents or cleaners containing ammonia since the resulting chemical reaction can form a potentially dangerous gas.

About ten years ago products began appearing in the market that were specifically designed to clean and restore weathered wood surfaces such as decks and siding. Today there are a variety of such products available. Deck cleaners and restorers generally fall into one of three categories--chlorine bleaches, oxygen bleaches, or oxalic acid-based formulas. Each of these is discussed below.

Chlorine-Based Bleaches
Common types of chlorine bleach used in deck cleaning products are sodium hypochlorite, calcium hypochlorite and dichloroisocyanurate. The first two are typically used in laundry detergents while the last is a swimming pool additive. The most commonly recommended dilution is 3:1 (25% bleach). These chemicals are effective against mildew but do little to remove dirt or other surface deposits (which is why bleach alone does not get clothes clean). When used on wood decks, chlorine-based bleached products can do more harm than good. They can result in the wood's having a whitish unnatural tone due to the bleaching of natural components or a fuzzing of the wood's surface due to the loosening of small fibers during the cleaning process. Moreover, if not rinsed properly, the chlorine salt residues can result in premature graying of wood from the action of sunlight and problems with adhesion of a new coat.

As noted previously, household bleach and other products containing chlorine-based bleaches should not be mixed with
products containing ammonia.

Oxygen-Type Bleaches
Products in this category are usually based on disodium peroxydicarbonate, commonly known as sodium percarbonate (OxiClean), an ingredient present in some color safe fabric bleaches. Sodium percarbonate is a powder. When added to water it forms hydrogen peroxide--a common oxygen bleach--and sodium carbonate (soda ash). Hydrogen peroxide is commonly used as a disinfectant and a stripper of hair coloring. On wood it is effective in removing mildew stains and weathered gray residue from UV (sunlight) degradation. The sodium carbonate acts as a built-in detergent, removing dirt and other deposits. Thus, sodium percarbonate-based cleaners are effective in removing dirt, mildew and weathered gray residues. Once treated, the wood returns to its natural original appearance.

Oxalic-Based Products
Certain wood species such as cedar and redwood contain natural resins known as tannins. These are water soluble materials which are reddish brown in color. Water can extract the resins from within the wood and deposit them on the surface, leaving brown or black discolorations. Tannins can also react with iron present in fasteners or nails resulting in blue-black stains. Neither chlorine bleaches nor oxygen bleaches are effective against tannin stains or iron stains. Oxalic acid, on the other hand, solubilizes tannins and iron stains and renders them colorless. Thus, it is the material of choice for use on redwood or cedar. However it can discolor the wood (see below). However, oxalic acid is not as effective against mildew. For this reason some homeowners and contractors will treat redwood and cedar with a sodium percarbonate or chlorine-based cleaner and follow it up with an oxalic acid-based product if tannin staining is apparent. Concentrating oxalic acid is toxic and should be handled and used with car.

Paint Strippers..........

Sometimes, in order to restore a wood deck and prepare it for refinishing, the previous finish, or what's left of it, will need to be removed. Most deck cleaners and restorers are not effective in removing paints and stains. This can be accomplished by mechanical removal or chemical means. Mechanical removal will be discussed in the next section.

Chemical paint strippers are usually based on organic solvents, caustic salts such as sodium hydroxide or sodium metasilicate. Most of these strippers are pretty potent and require some care in use and handling. Contact with skin or eyes must be avoided. Proper protective clothing and equipment must be worn as outlined on the product labels. Depending on the formulas, strippers will remove varnishes, oil-based stains or latex stains and paints. Most are supplied as ready-to-use liquids.

Residual amounts of the stripper should be thoroughly rinsed from the wood before any product is re-applied since residual traces of caustic salts can interfere with subsequently applied coatings.

Mechanical Cleaning..........

Mechanical methods for cleaning and restoring the surface of wood decks include planing, sanding, and power washing. Planing removes the outer surface of the wood face exposing fresh, new wood. Decking boards have to be removed from the structure and passed through a planer to accomplish this. Planing is very effective but its usage is limited by the need to physically disassemble part of the deck to carry it out. Since planing removes the outer veneer of wood it also results in a change in physical dimensions of each board.

Sanding is effective as a mechanical means for removing unwanted coats of previously applied finishes. It can, however, damage the surface of the wood. On redwood and cedar sanding often results in an excessive amount of tannin resin bleeding.

Power washing is the mechanical method for cleaning and restoring decks most favored by contractors. Power washers direct a pressure jet of water at the wood surface. This pressurized water is effective in removing dirt, mildew, algae and gray weathered residue from most wood surfaces. It can also be effective in removing previously applied coatings. Some contractors have found that the best cleaning procedure is to treat with a chemical cleaner and follow up with a wash/rinse from a power washer.

Power washers are available to homeowners through purchase or rent from many paint or home center stores. First time users need to be cautioned since excessive pressure can damage wood deck surfaces. If not used properly power washers can also cause damage to windows, doors and siding.
Major damage (in the form of texturing) can be done to smooth cedar by someone who was not experienced with a power washer!
For this reason many do-it-yourselfers prefer to stick to chemically based means of cleaning and restoring their decks.

Refinishing..........

As noted previously, proper surface preparation of weathered decks is an essential first step to the successful refinishing of these substrates. Failure to remove dirt, mildew and weathered residues is an open invitation for early failure of subsequently applied coatings.

Care should be taken to thoroughly rinse all cleaner/restorer products from the wood. In addition, many coatings require all dry surfaces prior to application, so contractors and homeowners should allow adequate time for the wood to dry before applying a finish.

Source: Cleaners And Restorers For Wood Decks And Siding at Historic HomeWorks.com

Products:
Mildew Removers and cleaners: Ranked by brightening results on cedar siding

  • Oxalic Acid - Best brightening, but didn't seem to be as good blech for mildew so deep mildew stains stood out more. Good for rust stains.
  • SuperDeck Wood Brightener - Will remove dirt, tannin discoloration, nail stains and rust stains caused by weathering and aging. (contains Sodium Hydroxide, Potassium Hydroxide, and Sodium Metasilicate.)
  • Bleach (3 to 1 water to bleach) (I found a 1:1 ratio was required for tough stains).
  • OxiClean - Sodium percarbonate - When added to water it forms hydrogen peroxide
  • The following weren't tested
  • SuperDeck Wood & Masonry Cleaner - Will attack the toughest stains caused by dirt, grease, mold or mildew. (contains Sodium Metasilicate)
  • Trisodium phosphate (TSP) - Removes dirt and grime. TSP mixed with bleach is particularly good for removing mildew from wood. The TSP alone can cause dark stains on redwood, and bleach prevents it.
Some cleaners don't list the content on the label. You can search for "product name" "Material Safety Data Sheet" OR MSDS to find it on the web.

My tests on cedar siding Strippers:
Bio-wash Stripex by Napier
SuperDeck Wood Stripper

At Sikkens Simply Beautiful Wood Care Products they say:
"When the deck has been stripped, it must be brightened with a deck brightener. This is a necessary step to neutralize the pH of the wood. The job will be ruined if you skip this step."

At MasterHandyman.com they say:
"If you have a cedar, redwood or hardwood deck, brightening with an oxalic acid-based brightener can discolor the wood. Wolman Cedar & Redwood Deck & Fence Brightener, Superdeck Brightener and Penofin Weatherblaster are made for these woods."

Links:
Cleaning at the painting page.
Refinishing Teak
Mold-Mildew-Agae
Paint Talk - Professional Painting Contractors Forum
Paint Forum - GardenWeb
painting chrome and plastics at Shadowriders.net
Basic Chemical Cleaning Families

last updated 12 Apr 2013