What reason can cause galvanized sheet rust

First, galvanized sheet in the whole service life cycle, the first corrosion is the oxidation of the zinc layer on the surface, generating "white rust". After a little longer, the "white rust" on the surface further reacts with carbon dioxide and other impurities in the humid air, forming "dark spots". When the galvanized sheet is used for a long time, the corrosion of the galvanized layer is serious, the steel base loses the "sacrifice anticorrosion" effect of zinc, and begins to oxidize, generating "red rust". Once the steel base begins to oxidize, the corrosion rate becomes rapid, and "the galvanized sheet ends its life.

Two, in addition to the galvanized sheet there are two special corrosion situation called "black". One is that the galvanized sheet in use for a period of time due to the influence of zinc and other elements in the zinc layer, the dull part of the zinc flower will be black, black galvanized layer still has a protective effect on the steel base, but has a certain impact on the life. The situation has improved considerably since the current use of lead was discontinued in favour of antimony to promote the formation of zinc flowers. Another situation is galvanized sheet in transportation, because of the small winding tension, between the steel strip layer is looser, Steel Coil contact pad wood parts will friction with each other and produce oxidation, white oxide is friction off, galvanized sheet surface black spots, this situation will make passivation film destroyed, galvanized layer thinning, galvanized sheet life greatly reduced, and denier appearance is also affected.

Three, galvanized sheet in thousands of dry environment or pollution-free environment corrosion resistance is very superior. But in a polluted environment, the life will be greatly shortened, so you have to do pre-smear-film processing into a color board after use, which is what we often say PPGI.