Standard steel commonly used anti-corrosion coating surface treatment
Steel To get good protection, does not depend on how good the paint used, the most critical is the degree of surface preparation. Surface treatment is like building a foundation, if the foundation is poor, the building will tilt, most notably in this regard Leaning Tower of Pisa in Italy. If the system does not paint a very good foundation (surface treatment), it will be shorter than expected service life, such as the original design life of ten years, the results of only five years, or worse, the result is within a year or even worse in the short term and lose effectiveness. Whether or shorten the life of the short-term deterioration of the coating system, means homeowners in the economy.
The actual painting industry experience also shows that the quality of the coating surface treatment performance itself has a greater impact than any other factor. Once you have selected the appropriate coating system, if the surface treatment is poor, the coating quality will be poor. Only good surface treatment, paint coating in order to play up its effectiveness.
For painting construction staff, must recognize the importance of surface treatment, so as to get the job done better. In the perspective view of the paint coating experts, the most important is the surface treatment before painting, rather than the paint itself. I have contacted a supermarket truss steel structure engineering, corrosion protection projects selected waterborne inorganic zinc primer dry film thickness of 40 microns, and in the actual construction process, the surface treatment only a simple wire brush rust, results be imagined. Surface treatment is usually required for new construction are Sa2.5 level best, but use only acceptable inorganic zinc-rich paint surface treatment requirements are Sa2.5 level. Therefore, the choice of surface treatment, the different requirements of the project, various coating properties, will have very different requirements on the surface treatment.
When judging the degree of surface treatment, we want to refer to a lot of standards. Surface treatment standards in practical work often encountered are:
(1) GB8923-88
(2) ISO8501-1: 1988
(3) SIS055900: 1967
(4) SSPC / NACE
Is China's national standard GB8923-88, ISO8501 international standard is now widely used, SIS055900 earliest influence in the world is also the largest standard. The United States is a strong scientific and technological forces, SSPC / NACE is the main criteria they use instead of using ISO international standard, and with the global promotion of NACE Coating Inspection Training Certification, and many steel design agencies use this standard, so China SSPC / NACE standards are often encountered.
Surface treatment standards are the most influential Swedish standard SIS0559001967, the standard originally developed by the Swedish Corrosion Institute, the American Society for Testing and Materials (ASTM) and the Steel Structures Painting Association (SSPC) developed jointly. Standards of other countries, such as Germany DIN55928, Denmark DS2019, etc. are set up on this basis. Sweden is now standard with international standards ISO8501-1: 1988 combined and replaced by the latter. Standard definition pictures and describe the greatest degree of retention.
China's national standard GB8923 equivalent use in ISO8501-1: 1988, so in this presentation here will not do more.
ISO8501-1: 1988 is a visual assessment of the corrosion of steel grades and surface treatment on the basis of grades, which includes 28 color photos and corresponding captions. 24 photos from the original Swedish standards, in addition to four from the fourth part of the original German standard DIN55928, Appendix 1 (August 1978), "organic coating to prevent corrosion of the steel structure, surface preparation and testing, photographs standard . "ISO8501-1 with a former Swedish standard main content, the main reasons are:
(1) SIS055900 has been recognized and widely used all over the world
(2) produced a new set of photos too expensive, but not necessarily have a substantial improvement
(3), previous and existing files in the established hierarchy of the corrosion-related standards in the future can not modify and continue to use without confusion
This part of ISO8501 slightly expand the scope of an earlier version than SIS055900, which includes in addition to scale and rust are also remnants of paint adhesion and steel surfaces other foreign matter.
ISO8501-1: 1988 will not paint over the original steel surface oxide coverage degree by degree and extent of corrosion is divided into four grades, respectively, A, B, C, D, said, and a corresponding picture controls.
A large area covered by adhering scale, and almost no rust steel surfaces
B has started to rust and mill scale has begun to peel off the steel surface
C scale because of rust and flaking been or can be scraped, but observed under normal vision to see only a small steel surface pitting
D scale has been due to corrosion and peeling observed in normal vision, has seen widespread steel surface pitting
ISO8501 for several levels of pretreatment methods and rust degree program jointly defined by the description of the surface state of the job as well as a typical model of rust after photos. Each grade are marked with pretreatment and clean-up methods used categories corresponding letter "Sa", "St" or "F1". If the letters have Arabic numerals, it clears the scale, extent and original rust coating. Photos marked with rust Rust grades and pre-existing levels of symbols before, such as BSa2½, expressed as a B-grade rust steel blasting to Sa2½ level.
There are 14 photos, ASa2½ to DSa3, they are represented by the abrasive quartz sand containing steel surface conditions were dry after cleaning spray. Many countries prohibit the use of abrasives containing quartz sand in a closed place, unless strictly controlled conditions. Therefore, other types and other colors are often used to dry abrasive blast cleaning. These abrasive steel surface may have a different appearance, then carefully clean even after still the case.
In the standard does not ASa1, ASt2 and ASt3 pictures, because these pre-treatment level can not be achieved, sufficient to represent the current picture characterized.
If you use the standard of "foreign body" is a term, which may include water-soluble salt and slag. These foreign bodies by dry blast cleaning, hand and power tools can not be completely cleared or scarfing removed from the surface, wet spray should be used to clean up. If oxide, rust or paint scraper to scrape the coating can be putty should be seen as not strong attachment.
(1) hand and power tools rust
Surface preparation by hand power tools, such as by hand shovel, wire brush, wire brush and motorized tools such as grinding machinery, and with the letters "St" represents. Before hand and power tool cleaning, any rust layer thickness should be eradicated visible grease and dirt should also be removed. After hand and power cleaning, the surface should be clear from dust and debris.
This standard does not establish pretreatment St1 grade level, because this level is not suitable to reach the surface coating.
St2 thorough hand and power tools rust
In the case without amplification was observed, the surface should be no visible oil and dirt, and almost no adhesion is not strong oxidation, rust, paint coatings and different debris. See photos BSt2, CSt2 and DSt2.
St3 very thorough hand and power tools rust
With St2, but the surface treatment is much more thoroughly, the surface should have a shiny metallic substrates.
See photos BSt3, CSt3 and DSt3.
(2) blast cleaning
Surface preparation to clean up the way the jet, with the letters "Sa" represents. Before blast cleaning, any rust layer thickness should be eradicated visible grease and dirt should also be removed. After blast cleaning, the surface should be clear from dust and debris.
Sa1 mild injection treatment
In the case without amplification was observed, the surface should be no visible oil and dirt, and there is no attachment is not strong oxide scale, rust, paint coatings and foreign matter. See photos BSa1, CSa1 and DSa1.
Sa2 thorough blasting
In the case without amplification was observed, the surface should be no visible grease and dirt, and almost without scale, rust, paint coatings and foreign matter. Any residues should be firmly attached. See photos BSa2, CSa2 and DSa2.
Sa2½ very thorough blasting
In the case without amplification was observed, the surface should be no visible oil and dirt, and without scale, rust, paint coatings and foreign matter. Any remaining traces of the stain should only be minor dot or striped. See photos ASa2½, BSa2½, CSa2½ and DS2½.
Sa3 apparent clean the steel blast cleaning
In the case without amplification was observed, the surface should be free of grease and dirt, and scale, rust, paint coatings and foreign matter. The surface should have a uniform metallic color. See photos ASa3, BSa3, CSa3 and DSa3.
(3) Flame rust
Surface pretreatment of scarfing manner, with the letter "F1" indicates. Scarfing should include the final with a power wire brush to remove the attachment, hand wire brush to clean the surface of the flame heating operations generated amplitude reach coating requirements. Before scarfing, rust should eradicate any thick.
F1 flame rust
In the case without amplification was observed, the surface should be free of scale, rust, paint coatings and other foreign matter, any residual traces should appear as surface discoloration (shaded in different colors), different colors of shadow. See photos AF1, BF1, CF1 and DF1.
US Steel Coating Association SSPC (Steel Structure Painting Council) standards developed also in the world-wide impact of surface treatment standards, especially in North America. Two commonly used standard SSPC-VIS1 (steel surfaces dry blast cleaning guide and reference photos, 2002 Revision) and SSPC-VIS3 (power tools and hand tools to clean visual standard, 2003 Revision).
National Association of Corrosion Engineers NACE (National Association of Corrosion Engineers) and SSPC has conducted joint scientific research technology, in October 1994, NACE and SSPC jointly developed and promulgated a new surface treatment standard SSPC / NACEVIS1. It should be noted, NACE and no hand and power tools rust standards.
Compared with the previous version of the standard, is to increase the original state of the coated surface of the paint and after the appearance of the treated.
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