Metal surface will usually accompanied by dust, grease, oxidation, rust, pollutants, salinity or loosening of the old film, in which scale is relatively common, but most overlooked parts. Oxide in iron and steel produced by hot forging forming of a compacted oxide layer, usually attached to the comparison, but compared to the steel itself is more brittle, and its own cathode, will accelerate the corrosion of metals. If you do not clear these materials, direct coating, it will affect the whole coating adhesion and corrosion resistance. According to statistics, about more than 70% paint problems are caused due to improper surface treatment. Therefore, suitable surface treatment for metal anticorrosion coating paint system is essential.
(1) metal anti-corrosion surface cleaning steps
1) eradication of all kinds of loose material.
2) solvent to remove grease.
3) using a variety of hand and power tools or methods such as sand paint on the surface until it meets the standards.
(2) metal anti-corrosion coating surface treatment method
1) solvent cleaning. Using solvents or lotion to remove surface oils and other similar contaminants. Various hand or power tools or sand could not remove the metal grease, solvent cleaning must be made prior to using other approaches.
2) hand tools clean. Usually using a wire brush, sandpaper, scrape, chisel or a combination of methods, removing iron and steel and other surfaces, loose scale, old paint and rust. This method is typically slower, only when other methods cannot be used. Usually treated with the method of metal surface cleaning degree is not very high, light corrosion occasions only.
3) motor vehicle clean. Using hand-held mobile tools such as a rotating wire brush, grinding or sanding machines, tools such as hammers or needle gun for cleaning. Use this method to remove loose scale, damaged old paint and rust, and so on. This method have higher efficiency than hand tools, but not suitable for heavy duty or immersed.
4) sand. Practice has proved that, whether it be at the construction site or in the workshop, sandblasting treatment is the most effective way of scaling. This is necessary for successful use of a variety of high performance paint system processing. Sand blasting cleaning must provide a common standard, preferably in standard picture references and provisions during the operation and control of surface roughness. Surface roughness depends on several factors, but mainly by the use of abrasive types and size and method of applying force (such as high pressure air or centrifugal force) effects. High pressure air, nozzle pressure and its effect on surface roughness of workpiece is in terms of determinants for centrifugal or mechanical injection methods, injection rate of operation is very important. Primer on the sand immediately after processing is complete. Sand also has some limitations. It cannot remove old coatings such as asphalt, grease and thermoplastic coatings surface of metal cannot be cleared of salt could be attached: it will bring dust problems and the high cost of dealing with waste; abrasive cost is relatively high.
5) acid-washed clean. Cleaning is an ancient plant pickling method, used to remove iron oxide skin on. There are still several steps to be used, usually for a two-tier system including acid passivation of corrosion and acid. Pickling and cleaning a downside is that it can clean the steel surface, but very low roughness, and surface roughness of high helped to improve heavy anticorrosion paint adhesion.
6) clean–burning. Acetylene flame for this method is the use of high-temperature and high-speed surface treatment, to remove all loose scale, rust, and other impurities, and then to wire brush polished. Treated surfaces must be free of oil, grease, dust, salt and other impurities.
(3) non-ferrous metals and chemical corrosion protection of zinc-plated iron
1) aluminum. Solvent cleaning, steam cleaning and other recognized chemical pretreatment of surface treatment methods are acceptable. Paint before sanding the surface and choose the right primer.
2) copper and lead. Solvent cleaning and hand polished, or very careful of sand (use low pressure and non-metallic abrasives), surface treatment result could be obtained.
3) galvanized iron. Should use relative reactive metals, iron and steel into the original as an anode cathode, thereby controlling the corrosion. In this case, as the active metal of the anode will inevitably corrode, so this method is also called a sacrificial anode anti-corrosion control. Zinc–coated or galvanized iron corrosion control by this mechanism. New galvanized steel surfaces, in front of the painting must be cleaned with solvent to remove surface contaminants. Also recommend the use of corrosive zinc–rich primers or primers pretreatment. Galvanized immediately after passivation of galvanized iron must be aged for several months, then used corrosive primers or zinc–rich primers pretreatment. Another way to Polish, remove the passivation layer on the surface.