In some special occasions, such as chemical plants, smelters, thermal power plants and so on must use special materials and structure of the thermal resistance and thermocouple.

There are three kinds of wear resistant coatings. The material hardness is HRC58-62, temperature range is 0－600℃、0－800℃（A）、0－1000℃（B）. Corrosion-resistant coatings have good anti-corrosion performance. In addition to melt molten lithium, potassium, sodium, hydrofluoric acid, chlorine trifluoride, it almost can resist all of chemical media. It can be long-term used within the 0-250 ℃. If the fixed thread is made into corrosion-resistant structure, then the thread can not work under pressure environment.