A ceramic coating is applied to the substrate to increase corrosion resistance. The ceramic coating is formed by melting a ceramic rod using a mixture of oxygen and acetylene, then atomizing it into minute droplets and spraying onto the substrate. Here are the specific steps:
Substrate surface pretreatment
In order to make the coating and the substrate have good adhesive strength, the surface of the coated substrate must be pretreated as follows: purification treatment, solvent cleaning, alkali cleaning, ultrasonic cleaning, heat treatment, and etc.
After the purification, the surface of the substrate is treated by grit blasting to roughen the surface of the substrate to form a good adhesion to the coating. The main methods of roughening the surface include sandblasting and roughening, spraying self-adhesive metal layers, troughs, embossing rolls, and flat grooves.
Ceramic spraying is performed on a rough substrate. The thickness of the ceramic coating can be controlled according to actual needs (optimum thickness is 0.3mm~1.0mm). For the complex shape of the workpiece, it can be placed on a lathe and other fixtures for ceramic spraying.
If the requirements on the surface of the workpiece are relatively fine, grinding is required after spraying. If it is a corrosion-resistant part, such as an acid-resistant pump casing, it also needs to be “sealed”. Since the ceramic coating has a certain gap, its porosity is about 4 to 12%, and the pores are connected to each other and extend from the surface to the substrate. In order to prevent corrosive media from penetrating the matrix through the pores, it is necessary to close the micropores.
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