Valve corrosion:
A uniform corrosion of metal surface metal valve in the atmosphere or solution complex working conditions not only time, also prone to pitting, part of the metal on the crevice corrosion, intergranular corrosion, delamination corrosion, stress corrosion, selective corrosion, erosion corrosion, cavitation corrosion and fretting corrosion. The local corrosion of hydrogen corrosion etc..
Improved process and valve structure:
Corrosion protection valve is designed from the start to consider the issue, a reasonable structure design, the correct method of valve products. There is no doubt that the slow corrosion of the valve is a good effect.
- Therefore, the design and manufacturing departments should deal with those parts which are unreasonable in structure design, incorrect in process and easy to cause corrosion. For different types of valve parts corrosion.
- Austenitic stainless steel valves to prevent intergranular corrosion is conducted by “quenching”, which is heated to 1100 DEG centigrade water quenching, containing titanium and niobium, and the carbon content in austenite stainless steel under 0.03%, reduce production of chromium carbide.
- Stress corrosion occurs under the action of corrosion and tensile stress. To prevent stress corrosion; heat treatment to eliminate or reduce the welding, cold processing of stress, improve the structure of the valve can not be avoided to avoid stress concentration, the use of electrochemical protection, spray paint. Adding corrosion inhibitor and applying compressive stress.
Wear corrosion is a form of corrosion of the fluid on the wear and corrosion of metal corrosion is a common corrosion of the valve, the corrosion occurred in the sealing surface for more. Methods: corrosion resistance, wear resistant materials, improved structural design, the use of cathodic protection, etc.. - Fretting corrosion is two parts contact with each other at the same time to bear the load, the contact surface damage due to fretting corrosion caused by vibration and sliding in bolted joints, stem and close the connection parts, ball bearings and shaft between etc.. Can be used to grease, reduce friction, surface phosphating, the choice of cemented carbide, as well as the use of tile or cold processing to improve the hardness of the surface protection methods.
- The corresponding protective measures should be adopted after annealing. To improve the surface roughness of the valve stem and the surface roughness of the other valves, the higher the surface roughness, the stronger the corrosion resistance. Processing technology and structure improvement of packing and gasket, the use of flexible graphite and plastic packing, flexible graphite gasket and sticky with PTFE gasket, can improve the sealing performance, reduce the corrosion to the stem and the flange sealing surface.
