Solvents such as water, mineral spirits, xylol, toluol, etc., are used to remove solvent-soluable foreign matter from the surface of ferrous metal. Rags and solvents must be replenished frequently to avoid spreading the contaminant rather than removing it. Low-pressure (1500-4000 psi) high volume (3-5) gal./min.) water washing with appropriate cleaning chemicals is a recognized “solvent cleaning” method. All surfaces should be cleaned per this specification prior to using hand tools or blast equipment.
Power Tool Cleaning
A mechanical method of surface preparation widely used in industry and involving the use of power sanders or wire brushes, power chipping hammers, abrasive grinding wheels, needle guns, etc. Although usually more effective than hand tool cleaning, it is not considered adequate for use under severe exposure conditions or for immersion applications.
White Metal Blasting
(SSPC-SP5), (SSI-Sa 3), or (NACE #1)
The removal of all visible rust, mill scale, paint and contaminants, leaving the metal uniformly white or gray in appearance. This is the ultimate in blast cleaning. Use where maximum performance of protective coatings is necessary due to exceptionally severe conditions such as constant immersion in water or liquid chemicals.
(SSPC-SP6), (SSI-Sa 2), or (NACE #3)
All oil, grease, dirt, rust scale and foreign matter are completely removed from the surface and all rust, mill scale and old paint are completely removed by abrasive blasting except for slight shadows, streaks or discolorations caused by rust stain, mill scale oxides or slight, tight resides of paint or coating that may remain. If the surface is pitted, slight residues of rust or paint may be found in the bottom of pits: at least two-thirds of each square inch of surface area shall be free of all visible residues and the remainder shall be limited to the light residues mentioned above.
Near White Blast
(SSPC-SP10), (SSI-Sa 2 1/2), or (NACE #2)
In this method all oil, grease, dirt, mill scale, rust, corrosion products, oxides, paint or other foreign matter have been completely removed from the surface by abrasive blasting, except for very light shadows, very slight streaks or slight discolorations caused by rust stain, mill scale oxides or slight, tight residues of paint or coating. At least 95% of each square inch of surface areas shall be free of all visible residues, and the remainder shall be limited to the light discoloration mentioned above. From a practical stand point, this is probably the best quality surface preparation that can be expected to today for existing plant facility maintenance work.