Hand-Wiping Steel

Summary
This recommendation details methods for manually cleaning steel parts, fabrications, subassemblies, machinery, equipment and other components. The methods are suitable for use on new steel as well as on previously painted surfaces.

Equipment

• 2½ gal. plastic, hand-pump, tank-type garden sprayer
  or,
• Airless sprayer with 2 gallon pressure pot
• Measuring cup
• Shop cloths
• Synthetic abrasive pad
• Pedestal fans or oil-free compressed air for dryoff

Method

1. Mix 1 oz. to 10 oz. of Prepaint Cleaner for each gallon of water.
2. Adjust the nozzle to produce a fine spray.
3. Thoroughly wet the part with the solution. Allow 1-3 minutes contact time.
4. Wipe part dry with clean shop cloths, turn cloths frequently for best results. For areas where solution can become trapped, i.e., behind tack welded plates, force dry with oil-free shop air.
5. Once dry, the part is ready for coating application.

Troubleshooting

• Flash rust on hot rolled steel is usually caused by parts remaining wet too long after washing.
• Insufficient cleaning may result from low solution temperature, low solution concentration and/or lack of solution contact with surface.
• Avoid white streaking on clean parts by reducing solution temperature, strength, and/or wash time.

Tips

1. Solution Strength - Use the minimum amount of Prepaint Cleaner required to clean the part.
2. Use Hot Water - If possible, mix cleaner with hot tap water. Each 18ºF increase in cleaning solution temperature doubles the rate of cleaning.
3. Spray, Don't Dip - Using a sprayer for application insures that the cleaning solution is uncontaminated. Rinsing the cleaning cloth in a pail of solution mixes soil removed from the surface with the solution and reduces cleaning effectiveness.
4. Prevent Flash Rust - When steel parts remain wet too long after cleaning, flash rust develops. This can occur even if the cleaning solution contains a rust inhibitor. To avoid flash rust, dry parts immediately after cleaning.
5. Synthetic Abrasive Pad - Use a synthetic abrasive pad on tough soils like welding smoke film.
6. How Clean is "Clean"? - Most steel has mill oil, processing lubricants and, in the case of hot rolled steel, heat scale. Oils, lubricants and coolants must be removed during cleaning to avoid paint problems. Most coatings will tolerate some heat scale on the surface, however, heavy deposits may compromise coating adhesion.
7. Cleaning Tests - After cleaning, lubricants, oils and coolants will show up as dark spots on the surface and also may show a sheen. Heat scale is less visible. Use the following tests to determine if the contaminants have been removed:
   -Spray water on questionable areas and watch for "water-break" or beading. If the water does not sheet over the surface, oil or other lubricants remain on the surface and must be removed before coating.
   -Wipe the underside of horizontal surfaces with a white cloth to check for heat scale. Usually, a light smudge on the cloth is not sufficient to cause a coating problem. If the cloth shows a heavy black smudge, affected areas should be recleaned and the process should be altered to insure that the underside of horizontal surfaces are clean.

For Technical Assistance Call:
1-800-888-1105