SURFACE PREPARATION FOR BONDING, COATING OR PAINTING

The success of any bonding, coating, or painting project depends largely on how well the surface is prepared. While the proper choice of a coating is important, a failure is almost always due to improper surface preparation rather than a failure of the coating materials.

The following guidelines should help you determine the proper preparation of most surfaces. Where there are special requirements for a particular type of coating material (epoxy, polyester, alkyd, polyurethane, etc.) these will be noted in the preparation description.

While there are many acceptable methods of surface preparation, we have attempted to choose those which are the best for each particular material.

ABS Plastics

1. Degrease with mineral spirits.
2. Abrade with emery cloth or Scotchbrite pad
3. Degrease again

Aluminum

1. Degrease with solvent-type degreaser or TSP
2. Abrade with 80 grit emery cloth
3. Degrease again
4. For bonding, no other treatment is required. For coating or painting, apply zinc chromate primer or vinyl wash primer per the manufacturer’s recommendation.

Ceramics

See Glass

Concrete

1. Degrease with TSP
2. Acid etch with 5% hydrochloric acid until a surface similar to 100 grit sandpaper is achieved
3. Rinse with plenty of clean water

Note: Repeat steps 2 & 3 as often as needed

Copper, Brass & Bronze

1. Degrease with solvent-type degreaser or TSP
2. Abrade with emery cloth
3. Etch a mixture of: .75 Gl 42% Ferric Chloride

1.50 Gl Concentrated Nitric Acid

10.00 Gl Water

4. Rinse in clean water

Fiberglass

1. Degrease with mineral spirits, MEK solvent or TSP
2. Abrade with sandpaper or other abrasive medium
3. Remove dust with tack rag
4. Do not wipe with acetone

Galvanized Metals

1. Degrease with TSP
2. Abrade with emery cloth
3. Recoat immediately

Note: Polyesters are NOT SUITABLE for bonding or coating of galvanized materials.

Glass

1. Degrease with solvent-type degreaser or TSP
2. Frost with wet / dry sandpaper and water
3. Warm for 30 minutes at 212°F in oven or boiling water
4. Coat or bond before glass reaches room temperature

Natural Rubber (Latex)

1. Treat the surface for 5 – 10 minutes with concentrated sulfuric acid
2. Rinse with clean cold water followed by clean hot water
3. Dry thoroughly

Note: Flex the rubber – the appearance of small hairline cracks indicates the rubber is ready for bonding. Repeat treatment if necessary.

Nylon

See ABS Plastics

Plexiglass

See ABS Plastics

Polycarbonate

See ABS Plastics

Polyethylene & Polypropylene

Note: These materials are generally not able to be coated or bonded. However, some limited success has been reported using the following technique:

1. With the blue part of a flame from a blow torch, lightly flame until shiny. Take care not to melt the surface. This method has proven most effective for bonding only.

Plolystyrene

See ABS Plastics

PVC

See ABS Plastics

Steel – Mild

1. Degrease with solvent-type degreaser or TSP
2. Abrade with emery cloth
3. Etch with phosphoric acid
4. Rinse in clean water
5. Dry thoroughly and recoat immediately

Steel – Stainless

1. Degrease with trichloroethylene
2. Etch with mixture of:

Oxalic Acid 18lb.

Concentrated Sulfuric Acid 1 gal.

Water 15 gal.

3. Rinse in clean water
4. Dry thoroughly before cleaning

Synthetic Rubber

See Natural Rubber

Note: If the sulfuric acid treatment fails to produce the hairline cracks on synthetic rubber, repeat the process using concentrated nitric acid.

Wood

1. Abrade with sandpaper
2. Remove dust

Zinc & Zinc Alloys

See Galvanized Metals

WARNING! SOME OF THE CHEMICALS SUGGESTED IN THE ABOVE PROCEDURES ARE HAZARDOUS! THE ORDER OF MIXING OF SOME FORMULAS IS CRITICAL.

GET DETAILED INSTRUCTIONS FROM A QUALIFIED CHEMIST BEFORE ATTEMPTING TO MIX FORMULAS CONTAINING ACIDS.

WHEN MIXING ACIDS AND WATER, ALWAYS ADD ACID TO WATER AND NEVER WATER TO ACID.