Whe the galvanized coil is exposed to the air, the key problems are dry etching, wet cold etching and wet etching.
Dry etching of galvanized steel sheet means that the surface of steel sheet is not eroded by continuous electrolyte water film when the air humidity is less than 30%. In this case, the corrosion rate of steel is relatively slow. But this kind of natural
environment standard is less.
The wet cold etching of galvanized steel sheet refers to the etching of steel sheet in ambient air with air humidity more than 30% and less than 100%. In this case, there is dust on the surface of steel, and there are
micropores and crevices in the rust layer, which cause the microscope to absorb and produce shrinkage water invisible to human eyes. The principle of galvanic cell is produced under the shrinkage water, and the etching rate is relatively fast.
etching of galvanized steel sheet refers to the etching of galvanized steel sheet when there is solidified shrinkage water on the surface of galvanized steel sheet in humid and cold environment with air humidity over 100%. In this case, the shrinkage
water on the surface of the steel is too thick, so that the diffusion rate of oxygen to the surface of the steel after melting is relatively slow, which reduces the etching rate. In fact, the corrosion of steel is closely related to the shrinkage water
on the surface between the two. What's more, with water, CO 2 is dissolved in the water, which makes iron produce weak electrolyte and a series of weak electrolyte reactions.
Te CO2 in the gas is continuously dissolved in the water, and the reaction
is continuously carried out. Because the key product is bright red, the material after iron air oxidation is generally called "red rust". Red rust is sparse
Loose, very easy to melt, unable to maintain the steel surface, do not re etch, to promote
the corrosion of steel has been carried out until it is completely etched, it is the characteristics of steel. Because of this, steel must rely on the surface coating of other metal materials or metal material protective layer thickness, in order to reasonably
avoid steel corrosion