97精品久久久久久久久精品,情品网站黑人,免费观看黄网站在线播放,欧美亅性猛交内射

Firstly, choose the correct materials. The valve body material needs to consider corrosion and pressure and temperature resistance.

Secondly, under low pressure and temperature conditions, using non-metallic materials as valve body materials can often effectively prevent corrosion.

In addition, the outer surface of the valve body is also subjected to atmospheric corrosion, and generally steel materials are protected by painting.