Is the zinc content in zinc-rich primers important for corrosion resistance?

Zinc-rich primers, the most commonly used primer material in the field of industrial heavy anti-corrosion, are widely coated, but many people have this cognitive misunderstanding: the higher the zinc powder content in the paint, the better. In fact, the zinc content refers to the specific content of zinc powder after the paint film drying, the higher the zinc powder content, the resin content in the paint will be reduced, resulting in a decrease in film, and then affect the adhesion between the paint film and steel. How much zinc content of metal can better play the anti-corrosion and rust-proof effect?anti-corrosion principle of zinc-rich primers is based on the sacrifice of anode zinc to protect cathode iron, similar to the principle of inlaid zinc blocks
Intransia) in parts below the sea
.
refore, some experiments show that the anti-corrosion performance of zinc-rich primer increases sharply with the increase of zinc content, and the high and low content of zinc-rich primer has a direct effect on anti-corrosion performance.
the zinc content of zinc-rich primers are clearly defined in the relevant standards. For example, in the SSPC PAINT 20 standard, the content of zinc-rich coatings in the dry film is divided into three grades:
the first grade dry film zinc powder
content ≥8
5%;
the international standard ISO12944 stipulates that the minimum zinc powder content in zinc-rich primers is 80%.
China's national standard as follows:
according to the type of paint base of zinc-rich primers are: I-type and II.type:
-type: inorganic zinc-rich primer, including solvent-based inorganic zinc-rich primer and water-based inorganic zinc-rich primer
;
Each type is divided into three categories according to the non≥-volatile zinc content of metals:
-1: non-volatile points in the metal zinc content ≥8
0
≥%;specifies a relatively high zinc powder content, because of exposure to corrosion environment of steel, if zinc content is low in zinc-rich primer, then the particle zinc powder can not form a complete zinc powder layer, cured epoxy resin conductivity is poor, greatly hindering the chemical protection of zinc powder, affecting the anti-polar protection of zinc-rich primer on steel. Therefore, having a certain high zinc content is an important technical index to ensure the corrosion resistance of zinc-rich primers.content of zinc powder is too high, zinc-rich primer corrosion resistance may not be good. Zinc powder content is too high, natural zinc-rich primer resin content will be reduced, film content will be reduced, paint film and steel adhesion is reduced. Therefore, once water and so on penetrate into the surface of zinc powder, causing abdominal trouble, the volume increases, so that the coating foaming possibility becomes greater.water resistance and salt spray resistance of zinc-rich primers are also important indicators. Zinc content in zinc-rich primer is low, because zinc powder particles can not form a complete zinc powder layer, zinc cathode protection effect is not obvious, salt spray test will soon appear rust, but due to low zinc content, resin content will increase accordingly, its salt water resistance is better. With the increase of zinc powder content in zinc-rich primer, cathode protection is enhanced. However, such as zinc powder is too high, resin reduction, substrate and coating adhesion weakened, resulting in saline solution penetration, causing zinc corrosion, and finally lead to paint foaming, resulting in reduced water resistance.
: It is necessary to enforce zinc content in national standards and international standards.