NACE (National Association of Corrosion Engineers) and SSPC (The Society for Protective Coatings) are two professional organizations focused on the protection of materials from corrosion and degradation. Both organizations are recognized authorities in the field and provide education, training, and certification programs for individuals involved in the protection of materials.
To create a unified voice for the corrosion control and protective coatings industries, a new association was launched in 2021. The new organization, the AMPP (Association for Materials Protection and Performance) was formed by a merger between both associations.
NACE and SSPC have developed a series of standards for surface preparation and cleaning of steel substrates prior to the application of protective coatings. These standards are used as a basis for specifying the level of surface cleanliness and preparation required for a given coating project. They help to ensure that the surface is properly cleaned and prepared, which is essential for the proper adhesion and performance of the protective coating.
Here is an overview of some of the SSPC/NACE surface preparation standards:
SSPC-SP1: Solvent Cleaning: This standard specifies the minimum requirements for the use of solvents for the removal of oil, grease, dirt, and other contaminants from steel surfaces prior to coating. SP1 is a prerequisite to the other SSPC abrasive blasting specifications. After solvent cleaning, dust is to be removed. The specification lists several different ways in which solvent cleaner may be applied to the surface including wiping or scrubbing the surface with solvent, spraying solvent directly onto the surface, vapor degreasing, immersion, alkaline cleaners, and steam cleaning.
SSPC-SP2: Hand Tool Cleaning: This standard specifies the minimum requirements for the manual removal of loose paint, rust, and other surface contaminants from steel surfaces using non-powered hand tools.
SPC-SP3: Power Tool Cleaning: This standard specifies the minimum requirements for the removal of loose paint, rust, and other surface contaminants from steel surfaces using power tools. The preparation method is intended to remove the same contaminants from a surface as in SSPC-SP2. It includes using rotary, impact, or power brushing tools to remove stratified rust, weld slag, and mill scale.
SSPC-SP5 / NACE1: White Metal Blast Cleaning: This standard defines the requirements for achieving a near-white metal cleanliness level on the surface, which is the highest grade of abrasive blast cleaning. No shadows, streaks or stains are permitted. When viewed without magnification, the surface shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products and other foreign matter.
SSPC-SP6 / NACE3: Commercial Blast Cleaning: This standard specifies that all tightly-adhering matter must go. Commercial blast cleaning is used when the objective is to remove all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products, and other foreign matter, leaving staining or shadows on no more than 33 percent of each unit area of the surface.
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SSPC-SP7 / NACE4: Brush-Off Blast Cleaning: When viewed without magnification, the surface shall be free of all visible oil, grease, dirt, dust, loose mill scale, loose rust, and loose coating. Tightly adherent mill scale, rust, and coating may remain on the surface. Mill scale, rust, and coating are considered tightly adherent if they cannot be removed by lifting with a dull putty knife. This blasting method cleans less aggressively than an industrial blast clean.
SSPC-SP10 / NACE2: Near-White Metal Blast Cleaning: This standard requires the surface to be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products, and other foreign matter when viewed without magnification. It specifies that shadows, streaks and stains must be limited to 5% of the surface area.
SSPC-SP11: Power Tool Cleaning to Bare Metal: This standard requires the surface to be free from all visible oil, grease, dirt, dust, rust, coating, oxides, mill scale, corrosion products, and other foreign matter when viewed without magnification. However, some rust remaining at the bottom of pits is acceptable if the surface was pitted to begin with. A surface profile of no less than 1 mill (25µm) between peaks and valleys is required. Grinding tools and impact tools are both acceptable means for achieving the level of cleaning specified. Oil, grease, and dust must be removed both before and after the cleaning procedure.
SSPC-SP14 / NACE8: Industrial Blast Cleaning: This standard specifies that 90% of the tightly-adhered matter must go. Shadows, streaks and stains from rust, mill scale and old coatings are allowed on 100% of the surface. It is specified for conditions when the existing coating is well-adherent and compatible with new coating.
SSPC-SP16 Brush-Off Blast Cleaning of Coated and Uncoated Galvanized Steel, Stainless Steels, and Non-Ferrous Metals: Use of this surface preparation standard roughens and cleans the bare substrate including a hot-dip galvanized coating to create a profile suitable for painting. Completion of this process produces a profiled surface free of all visible oil, grease, dirt, dust, corrosion products, and other foreign matter when viewed without magnification. The standard also specifies the procedures for use on galvanized steel including inspection for a passivation treatment and wet storage stain.
In conclusion, surface preparation is an important step in the process of protecting steel structures from corrosion and degradation. Proper surface preparation is critical to the performance and longevity of protective coatings and linings and is key to ensuring the protection of the underlying structure.