Types of Surface Preparation

Surface Preparation Methods

MINIMAL PREPARATION

For coatings requiring only minimal surface preparation, the surface needs to be prepared in accordance to SSPC-SP 1 and SSPC-SP 2 or SSPC-SP 3. Tightly adhered rust, mill scale or previous coating can remain provided it cannot be removed by lifting with a dull putty knife using moderate pressure. Use SSPC-SP 7 (NACE 4) to expedite the preparation of large areas.

CHEMICAL CLEANING METHOD

SSPC–SP 1: Chemical Cleaning

This method involves the removal of dirt, oil, grease and other foreign materials with organic solvents, detergents or commercial cleaners using one of several cleaning methods such as wiping, steam cleaning, or vapor degreasing. Use one or more of the following techniques.

Chemical Cleaning Methods

Pure Strength Cleaner/Degreaser: Removes dirt, grease, oil, adhesives, road tar, and more. Agitate for one minute before use. Apply directly on the surface, rub with a brush or cloth, and rinse thoroughly with clean water or wipe with a damp cloth. For large jobs dilute Cleaner/Degreaser with water. All surfaces must be dry before coating is applied.

Steam Cleaning: Recommended for removing grease, oil, salt, acid, alkali, and similar chemical residue from large areas. For maximum effectiveness, steam cleaning should be used in combination with alkaline cleaning. The surface must be thoroughly dry and free of residue before it is coated.

Alkaline Cleaning: For removal of dust, dirt, wax, grease, oil, fat, salt, acid residue, etc., scrub surface with a strong commercial detergent solution such as trisodium phosphate (TSP), then flush thoroughly with fresh water. Surface must be completely dry and free of any residue before it is coated.

Volatile Solvent Cleaning: Make certain the area is well ventilated. Apply solvent to the surface with cloths, sponges, or brushes and scrub to remove grease and oil. Several successive wipings are usually necessary, using clean cloths and solvent each time. For optimum results follow with Alkaline Cleaning.

HAND AND POWER TOOL CLEANING METHODS

SSPC–SP 2: Hand Tool Cleaning

Loose rust, loose mill scale and deteriorated coatings can be removed by effective use of hand and power tools. Brush-Off Grade Blasting (SSPC-SP 7) cleans to the same requirements and may be used as an alternative to scraping and wire brushing. Prior to scraping and wire brushing, remove grease, oil, salt, chemical dust, and other contaminants by Chemical Cleaning. Removal of heavy rust scale, light mill scale, or previous coatings over extensive areas usually requires Commercial Grade Blast Cleaning (SSPC-SP 6) or Industrial Blast Cleaning (SSPC-SP-14).

Chip, scrape, or wire brush rusted surfaces thoroughly to produce a tightly adhered surface that is clean and free of foreign matter to assure good coating adhesion. Care must be taken with power tools to avoid polishing a metal surface or abrading it too deeply. Tightly adhered coatings which are very hard or glossy should be sanded to remove gloss and slightly roughen the surface. This will contribute to maximum adhesion of the new coating. Examine existing coatings carefully for signs of rust beneath the coating. If present, remove coatings in these areas.

SSPC–SP 3: Power Tool Cleaning

Tightly adhered coatings which are very hard or glossy should be sanded to remove gloss and slightly roughen the surface. This will contribute to maximum adhesion of the new coating. Examine existing coatings carefully for signs of rust beneath the coating. If present, remove coatings in these areas.

SSPC–SP 11: Power Tool Cleaning to Bare Metal

Power tool cleaning to produce a bare metal surface and to retain or produce a surface profile. This cleaning specification exceeds SSPC-SP 3 Power Tool Cleaning in that it requires complete removal of all visible oil, grease, dirt, mill scale, rust, paint, oxide, corrosion products, and other foreign matter. Slight residues of rust and paint may be left in the lower portions of pits if the original surface is pitted. If the surface is to be roughened, the surface profile produced shall be not less than 1 mil (25μ) and shall be to a degree suitable for the specified paint system.

SSPC–SP 15: Commercial Grade Power Tool Cleaning

Power tool cleaning to produce a bare metal surface. Remove all visible oil, grease, dirt, mill scale, rust, paint, oxide, corrosion products, and other foreign material. Random staining is allowed provided it is limited to no more than 33% per unit area of surface. A surface profile of 1 mil (25μ) shall be produced.

PRESSURIZED WATER CLEANING METHODS

These standards provides requirements for the use of high and ultra-high pressure water jetting to achieve various degrees of surface cleanliness. This standard is limited in scope to the use of water only without the addition of solid particles in the stream. These standards define four levels of working pressure:

SSPC-SP WJ-1/NACE WJ-1: Waterjet cleaning of metals. Clean to bare substrate.

SSPC-SP WJ-2/NACE WJ-2: Waterjet cleaning of metals. Very thorough cleaning.

SSPC-SP WJ-3/NACE WJ-3: Waterjet cleaning of metals. Thorough cleaning.

SSPC-SP WJ-4/NACE WJ-4: Waterjet cleaning of metals. Light cleaning.

This cleaning standard defines 4 levels of cleanliness for visible contamination by water jetting and 3 levels for non-visible contamination, such as chlorides and other soluble salts. See the full standard for complete definitions on the level of cleanliness.

ABRASIVE BLAST CLEANING METHODS

Abrasive blast is the most effective method of cleaning steel and masonry surfaces prior to coating. It is mandatory for certain specialized applications such as water immersion and high temperature exposure. Recommended for removal of mill scale, heavy rust scale, and previous coatings from large areas. Careful selection of equipment, nozzles, and abrasives are essential to economical operation and achievement of the desired results. Avoid using coarse abrasives. 18–40 mesh sand or grit will provide the 2 to 2.5 mil 50–62μ) blast profile recommended for use with most coating systems.

For optimum results, follow this sequence:

1. Prior to blast cleaning, remove grease, oil, salt, chemicals, dusts, and similar contaminants by Chemical Cleaning.

2. Prior to blast cleaning, remove all weld spatter.

3. Abrasive blast to one of the grades described below.

4. After blasting, remove all abrasive, dust and grit with a vacuum cleaner, clean and dry compressed air, or a clean brush.

5. Blasted surfaces should be coated on the same day they are blasted before the cleaned surface can become contaminated.

SSPC–SP 5 (NACE 1): White Metal Blast Cleaning

Completely remove all mill scale, rust, rust scale, previous coating, etc., leaving the surface a uniform gray-white color.

SSPC–SP 6 (NACE 3): Commercial Grade Blast Cleaning

Completely remove all dirt, rust scale, foreign matter, and previous coating, etc., leaving shadows and/or streaks caused by rust stain and mill scale oxides. Random staining shall be limited to no more than 33% of each unit area of surface (a unit of area is defined as 9 square inches).

SSPC–SP 7 (NACE 4): Brush-Off Blast Cleaning

Remove rust scale, loose mill scale, loose rust, and loose coatings, leaving tightly bonded mill scale, rust, and previous coatings. This is an ideal method for removing oxides and/or loose and peeling coatings from galvanized metal. Results are comparable to those achieved by through chipping, scraping, and wire brushing.

SSPC–SP 10 (NACE 2): Near White Metal Blast Cleaning

Remove all rust scale, mill scale, previous coating, etc., leaving only light stains from rust, mill scale, and small specks of previous coating. Random staining shall be limited to no more than 5% of each area of surface (a unit of area is defined as 9 square inches).

SSPC–SP 14 (NACE 8): Industrial Blast Cleaning

Removal of all visible oil, grease, dust, and dirt. Traces of tightly adherent mill scale, rust, and coating residues are permitted to remain on 10% of each unit area of the surface if they are evenly distributed (a unit of area is defined as 9 square inches). The traces of mill scale, rust, and coating shall be considered tightly adhered if they cannot be lifted with a dull putty knife. Shadows, streaks, and discoloration caused by stains of rust, stains of mill scale, and stains of previously applied coating may be present on the remainder of the surface.

CONCRETE, MASONRY, PLASTER AND WOOD (FLOORS OR WALLS)

New or Uncoated: Allow new substrate to cure thoroughly before coating. This requires 30 days under normal curing conditions. If there is any doubt about the dryness of the substrate, conduct a test by placing a weighted rubber mat, plastic sheet, or other non-porous material on the substrate for 24 hours. Then, check the underside of the mat and the substrate for signs of moisture. The substrate will be darker if damp. If moisture is found, substrate is too damp to coat with solvent-based coatings. Allow additional drying time of 10 to 14 days. Repeat test. If moisture persists, substrate cannot be coated (ASTM D 4263-83).

Very dense, non-porous, or finished concrete must be acid etched, or abrasive blasted, to assure proper coating penetration. Determine porosity by pouring about one ounce of water onto the substrate. If water soaks in, the concrete is porous enough for coating. If it beads up on the surface, the concrete is not porous enough, and treatment is warranted. All surfaces must be free of grease, oil, wax, salt, dirt, and other contaminants. Remove with one of the chemical cleaning methods. Acid etch with Rust-Oleum 108 Cleaning & Etching Solution (ASTM D 4260-83).

Uncoated Wood

Remove all loose dirt, dust, etc., by sweeping or vacuum cleaning. Remove floor compound or wax by appropriate method. The surface must be thoroughly dry before coating.

Coated Concrete and Wood

Remove loose dirt, dust, etc., by sweeping or vacuum cleaning. Remove grease, oil, floor compound, or wax by Chemical Cleaning. Scrape or sand carefully to remove deteriorated coatings. On concrete, deteriorated paint is best removed by abrading surfaces (ASTM D 4259-83). 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. 6000 and 6500 Systems can be applied over most existing floor coatings without lifting them. Refer to SSPC 13 (NACE 6) for additional and more complete information regarding the surface preparation of concrete.

Mildewed Surfaces

Surfaces with mold and mildewed areas should be cleaned with an alkaline cleaning solution and rinsed with water. If any mold or mildew remains on the surface, clean further with one quart of household bleach added to a gallon of water. Rinse with clean water. Severely mildewed areas should be cleaned with a chlorinated cleansing powder and thoroughly rinsed with water.