Ferrous Metal Surface Preparation

Steel should be cleaned by one or more of the 10 surface preparation methods described. These methods were originally established by the Society for Protective Coatings (formerly the Steel Structures Painting Council) in 1952. The surface preparation specifications, with updated modifications, are used throughout the world. Visual standards are available through the Society for Protective Coatings. Although these specifications are primariliy intended for heavy metal or plate, most are also suitable for light weight or thin section metal. Obviously, caution must be exercised when using methods such as blast cleaning on thin section metal since damage by warping or from excessive peening of the surface may occur.

Includes simple solvent wiping, immersion in solvent, solvent spray, vapor degreasing, steam cleaning, emulsion cleaning, chemical paint stripping and alkaline cleaners.

Solvent cleaning is used primarily to remove oil, grease, dirt, soil, drawing compounds and other similar organic compounds. Solvent cleaning may also be used to remove old paint by the use of paint removers or alkaline paint strippers. Inorganic compounds such as chlorides, sulfates, weld flux, rust and mill scale are not removed by cleaning with organic solvents.

Prior to the use of hand tools, remove visible oil and/or grease by power or hand washing. A surface prepared with hand tools requires that all loose mill scale, loose rust, loose paint and other loose foreign material be removed. It is not intended to remove adherent mill scale, rust and paint. Material is considered to be adherent if they can not be removed by lifting with a dull putty knife. Types of tools used include: non-woven abrasive hand pads, wire brushes, and scrapers. 3M Scotch-Brite Hand Pads can be used to accomplish this type of preparation.

Prior to the use of power tools, remove visible oil and/or grease by power or hand washing. A surface prepared with power tools requires that all loose mill scale, loose rust, loose paint and other loose foreign material be removed. It is not intended to remove adherent mill scale, rust and paint or to produce a surface profile. Material is considered to be adherent if they can not be removed by lifting with a dull putty knife. Types of power tools used are generally impact or rotary power tools, to which any of the following types of media can be attached: non-woven abrasive wheels and discs, coated abrasive discs, flap wheels, needle guns or other devices. 3M Scotch-Brite Surface Conditioning Products line can provide this type of abrasive media to be mounted onto power tools.

Removal of all visible rust, mill scale, paint, and foreign matter by blast cleaning by wheel of nozzle (dry or wet) using sand, grit, or shot. For very corrosive atmosphere where high cost of cleaning is warranted.

This is the most commonly specified grade of abrasive blasting and is suitable for most industrial coatings when not intended for immersion service. Prior to blast cleaning, visible deposits of oil and/or grease should be removed by power washing or other agreed upon methods. In addition, sharp fins, edges and weld spatter should be removed. A surface prepared according to SSPC-SP-6-85 requires that the surface, when viewed without magnification, be free of all visible oil, grease, dirt, dust, mill scale, rust, paint, oxides, corrosion products and other foreign matter. Light staining due to rust, mill scale, and previous coatings may remain on no more than 33% of each square inch of surface area. The unit area for determining staining shall be approximately 9 square inches (6400 square millimeters). The profile produced by blasting should be controlled by the selection of blast media and should not exceed the filling capacity of the primer to be applied.

A surface prepared according to SSPC-SP-7-85 requires that the surface, when viewed without magnification, be free of all visible oil, grease, dirt, dust, loose rust, loose mill scale, and loose coatings. It is not intended to remove tightly bonded mill scale, sound rust or adherent coatings. Material is considered adherent if it can not be lifted with a dull putty knife. Prior to blast cleaning, visible deposits of oil and/or grease should be removed by power washing or other agreed upon methods. A Brush-off Blast may also be used to abrade a previous coating, providing a surface profile for new coating application.

Complete removal of rust and mill scale by acid pickling, duplex pickling, or electrolytic pickling.

Prior to blast cleaning, visible deposits of oil and/or grease should be removed by power washing or other agreed upon methods. In addition, sharp fins, edges and weld spatter should be removed. A surface prepared according to SSPC-SP-10-85 requires that the surface, when viewed without magnification, be free of all visible oil, grease, dirt, dust, mill scale, rust, paint, oxides, corrosion products and other foreign matter. Light staining due to rust, mill scale, and previous coatings may remain on no more than 5% of each square inch of surface area. The profile produced by blasting should be controlled by the selection of blast media and should not exceed the filling capacity of the primer to be applied.

In areas where an abrasive blast is desirable but impractical, Power Tool Cleaning to bare metal may be used to prepare the surface. Prior to blast cleaning, visible deposits of oil and/or grease should be removed by power washing or other agreed upon methods. In addition, sharp fins, edges and weld spatter should be removed. The prepared surface will be free of all visible oil, grease, dirt, rust, paint, and other foreign matter. Residues of rust and paint may be left in the pits of the surface. This method may be used to produce a surface profile in small areas.

Surface cleaning power tools are generally impact or profile producing power tools, to which any of the following type of media can be attached: non-woven abrasive wheels and discs, coated abrasive discs, flap wheels, needle guns or other devices. 3M Scotch-Brite Surface Conditioning Products line can provide this type of abrasive media to be mounted onto power tools.

Standard reference photographs; recommended supplement to SSPC Surface preparation Specification SSPC-SP 5,6,7 and 10.

A geometric numerical scale for evaluating degree of rusting of painted steel. Illustrated by color photographs and black & white dot diagrams.

Standard reference photographs; recommended supplement to SSPC-SP 2, 3 and 11.