Coating Quality Defect Analysis - Coating Fragmentation

       The main reason for the cracking of the coating is the large tensile stress inside the coating. The main reasons for generating tensile stress are as follows.



       ①The spraying time of the spray gun in one place is too long, which makes the coating layer sprayed at one time too thick, which causes the coating to overheat and causes a large shrinkage after cooling; the thickness of the coating is uneven, and it shrinks during cooling. Thin areas are pulled apart.

       ②The spray gun is too close to the workpiece, which can also cause the coating to overheat and cause greater shrinkage during cooling.

       ③The working current is too large. The high temperature of the metal particles, in addition to excessive oxidation, can also cause the coating temperature to be too high.

       ④The spraying material (steel wire) contains more hot cracking and quenching elements, such as sulfur and phosphorus.

       ⑤ The workpiece after spraying suddenly comes into contact with cold air, and excessive quenching causes the coating to shrink sharply, causing the coating to crack.

       ⑥ There is excess oil mist and water vapor in the compressed air, which reduces the bonding strength between metals.