electro Galvanized steel coil
Corrosion of galvanized sheet What are the characteristics?
Corrosion (1) galvanized sheet over the entire service life cycle, the first thing that happens is galvanized surface oxide layer, generate "white rust." After a little longer, the surface of the "white rust" in humid air further with carbon dioxide and other impurities in the gas reacts "spots." When galvanized sheet using a longer time, more serious corrosion of galvanized layer after the steel group lost zinc "sacrificial" role, began to oxidation to produce "red rust." Once the steel base begins to oxidation, corrosion rate becomes very fast, "galvanized sheet will be over its lifetime.
(2) In addition there are two special galvanized for corrosion called "black patina." One is galvanized sheet in use for some time in the future because of the galvanizing layer lead elements in matte black part will spangle, black layer of the galvanized steel base is still a protective effect, just have a certain impact on life expectancy. This situation is currently out of use of lead and antimony to zinc has improved considerably after promoting flower formation. Another scenario is galvanized sheet in the transport, because the winding tension, loose layer between the steel strip, coil skids in contact friction between the parts will produce oxidation, after the white oxide are rubbed off, plating zinc plate surface black spots, this situation makes the destruction of the passive film, galvanizing layer thinning, galvanized sheet life greatly reduced, and the appearance is also affected.
(3) galvanized sheet in a dry environment or pollution of the environment is very superior corrosion resistance. But in the case of contamination of the environment, life will be much shorter, it must be treated as a color plate after laminating film use.
(4) Generally, corrosion is not a surface layer of galvanized sheet galvanized all uniformly etched, but in the coating and substrate binding poorer place first coating is etched, resulting in partial loss of the use of severe corrosion Performance. From this point in terms of adhesion, zinc coating, particularly the overall adhesion is good or bad is more important than the thickness of the zinc coating. If a local zinc coating adhesion is poor, even then a thick zinc coating, adhesive will not benefit from the initial corrosion. That with the "bucket principle" almost, is galvanizing production technician must recognize the problems.