High temperature resistance analysis of galvanized sheet
1. Basic introduction
A highly galvanized layer means that the plating layer is very thick, which is for hot-dip galvanizing because electro-galvanizing cannot be too thick.
The thickness of the hot-dip galvanized coating is generally above 20 microns, even up to 100 microns.
The weight of the galvanized layer per square meter usually expressed,
145 grams per square meter, the coating is about 20 microns.
However, it is not easy to control the thickness of hot-dip galvanizing in a relatively thin range.
2. The chemical properties make it resistant to high temperatures
The melting point of zinc is 419.5°C and it is chemically active.
In the air at room temperature, a thin and dense basic zinc carbonate film is formed on the surface to prevent further oxidation.
When the temperature reaches 225°C, zinc violently oxidized, showing white zinc oxide.
After high-temperature grilling, the surface anti-corrosion layer of the galvanized sheet oxidized,
so the galvanized sheet cannot withstand high temperatures, the heated surface will change color,
or other protective materials on the surface will easily turn yellow after oxidation.
The surface of the galvanized sheet should be free of oily or waxy components and other stains or dust, which can improve the adhesion of the putty;
Theoretically, it not recommended making decorative paint or primer on the basis of the surface of a similar galvanized sheet that is too smooth.
If necessary, corrosive treatment (such as hydrochloric acid) can improve the bonding strength with putty and paint;
Putty should correspond to the standard ratio adjustment and the ratio of curing agent.
The excessive proportion will reduce the adhesion and physical properties of putty (such as excessive brittleness and loss of toughness);
Putty should use within the shelf life and applied as thinly as possible to prevent excessive temperature difference between the surface
and the base material galvanized sheet, resulting in inconsistent stress, contraction, and expansion,
and layer shedding resulting in complete separation.