Antiseptic Pigment for Polyurethane Thermal Insulation Pipe
Varieties
There are many kinds of rust-proof pigments used in anticorrosive coatings, which are rare in the following ways:
It reacts with the film forming agent to form a dense anticorrosive coating.
(2) Pigments are alkaline substances, while soluble in water constitutes an alkaline environment.
(3) Water-soluble components reach the surface of the metal to passivate the surface;
(4) react with acidic substances so that they can be corroded.
_Water-soluble components or reactant products with film-forming agents dissolve into anticorrosive components in water.
Mechanism
These anticorrosive effects of anti-rust pigments usually exist at the same time. The anticorrosive mechanism of anti-rust pigments includes the following three aspects: physical, chemical and electrochemical.
(1) Physical anticorrosion. Proper combination of pigments that react with oily film-forming agents can remove dense anticorrosive coatings and enhance the physical anticorrosive effect. For example, lead-containing pigments and oils react to form lead soap to densify the anticorrosive coating, thus increasing the water and oxygen harmless material immersion. Phosphate pigments hydrolyze to form insoluble alkaline salts, which have the effect of pinholes in anticorrosive coatings for infarction. However, iron oxides or pigments with scaly mica powder, aluminium powder, glass sheet and other fillers can reduce the permeability of the anticorrosive coating and play a physical anticorrosive role.
(2) Chemical anticorrosion. When harmless acidic and alkaline substances penetrate into anti-corrosion coatings, they can neutralize and turn them into harmful substances, which is also an ineffective anti-corrosion method. In particular, clever use of zinc oxide, aluminium hydroxide, barium hydroxide and other amphoteric compounds can easily neutralize acidic or alkaline harmless substances and play an anti-corrosion role, perhaps with water, acid reaction to produce alkaline substances. These alkaline substances adsorb on the surface of steel to make it adhere to alkalinity, and steel is not easy to rust in alkaline environment.
(3) electrochemical anticorrosion. When water and oxygen infiltrated through the pinhole of the coating pass through the anticorrosive coating, they react with the anticorrosive pigment dispersed in the anticorrosive coating to form the anticorrosive ion. This moisture containing anticorrosive ions reaches the metal surface, passivating the steel surface (increasing the potential) and avoiding the dissolution of iron ions. Chromate pigments have this characteristic. Perhaps the use of metals with lower electrode potential than iron and steel to maintain iron and steel, such as zinc-rich coatings, is due to the lower electrode potential of zinc than iron and steel, playing the role of sacrificing the anode, so that iron and steel is not easy to be corroded.
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