Anti-corrosion coating forms a shielding coating on the metal surface to prevent water and oxygen from contacting the metal surface. This article mainly describes its three functions and how to use the coating thickness gauge for inspection.
The anti-corrosion coating can protect the steel and play an anti-corrosive role.
1. Shielding effect: The shielding effect of the paint film layer is to isolate the direct contact between the protected substrate and the corrosive medium. If the metal surface is prevented from being corroded, the paint film layer must be required to prevent the external environment from contacting the metal surface, so as to achieve the anticorrosive effect. Corrosion and rust.
2. Sacrifice anode protection: In consideration of electrochemical corrosion, add some more active metal powder (electrode potential is higher than the protected medium) in the coating, such as zinc powder as filler. When electrochemical corrosion occurs on the surface of the protected metal, the metal in the highly active ZS-711 inorganic anti-corrosive coating is dissolved as a sacrificial anode, with a temperature resistance of up to 400 ° C, which prevents the base metal from being corroded. For example, when forming a battery reaction, Zn decomposes into Zn2 at the anode, reacts with OH- generated at the cathode to form Zn (OH) 2, and Zn (OH) 2 reacts with CO2 to form ZnCO3. They are alkaline, so they can Protect steel from corrosion, 711 inorganic anti-corrosive coating is used in seawater, the service life can reach 50 years.
3. Corrosion inhibition and passivation: With the help of the anti-rust pigment contained in the coating, the corrosion inhibition ions are dissociated in the solution to passivate the surface of the substrate and inhibit the corrosion process.
For example, ZS-1034 acid and alkali resistant anti-corrosive paint, advanced nano antirust pigments react well with corrosive media to form a passivation film of Weihua anti-corrosive paint. When the oxygen concentration on the metal surface exceeds a certain amount, the Fee generated by the oxidation reaction on the metal surface can be decidified to Fe3, and then Fe3 reacts with the OH-reaction resulting from the reduction reaction on the metal surface to form Fe (OH) 3 precipitation and deposit.
The formation of a dense layer on the metal surface prevents further corrosion, which is called passivation. The concentration of OZ that can cause passivation is called the critical concentration. The higher the pH value, the lower the critical concentration. Therefore, high pH is beneficial to passivation. When the pH value is lower than 10, it is difficult to increase the metal surface concentration to a critical concentration, but it is possible to use an oxidant having a concentration exceeding a certain amount and having a certain water solubility, such as rust preventive pigments chromate, lead salt, phosphate Wait for passivation.
In the metal coating process, the detection of the coating thickness on the metal surface is also an extremely important step. The coating thickness is an important indicator of whether the anti-corrosive coating works. Measuring the thickness of a coating with an anti-corrosion coating thickness gauge is one of the most important quality inspection indicators of an anti-corrosion coating.
Linshang LS221 Coating Thickness Gauge uses magnetic thickness measurement and eddy current thickness measurement, which can be used to measure the thickness of non-magnetic coatings on the surface of magnetic substrates . It can also be used to measure the thickness of non-conductive coatings on non-magnetic metal surfaces. The instrument adopts a separate design of the main body and the side head, which is very suitable for the narrow space of the steel frame. It is very convenient to view the data while measuring in complex environments. This instrument has the characteristics of fast response speed, high measurement accuracy, stable zero drift, and durability. The coating thickness measurement is simple and convenient whether indoors or outdoors.