What is passivation? Does my product need it?
source：Qianye Precision time：2022-9-14
“My new stainless steel product specification requires’ passivation ‘. Do I need it?” Our answer is that you may not. That’s why.
Passivation is the process of protecting stainless steel from corrosion by adding an oxide layer on its outer surface. Although some stainless steel product specifications require passivation to reduce corrosion risk, most of them are unnecessary and expensive, and may damage some metal products, including flat bar springs, such as constant force, variable force and constant torque springs, all of which are uncommon products manufactured by Qianye precision.
The reason passivation is not a good idea for flat bar springs is because passivation involves the use of acids and harsh chemicals to initially clean the metal as part of the process. The geometry of these spring types means that many small cracks can form between the coil layers. The acid used in passivation can become trapped in these crevices. This resulted in longer-than-expected exposure of the stainless steel, which in turn resulted in hydrogen embrittlement and eventual spring failure. Additionally, mechanically exposing all surfaces of the spring to acid can damage the spring, resulting in changes in force/torque output or defects.
There are better, simpler, cheaper ways to avoid any need for corrosion and passivation of stainless steel components, and it’s as simple as choosing a fussy material. Remember that the risk of corrosion of any stainless steel component is driven by the environment (such as the presence of water and other chemicals) and Qianye Precision typically uses high quality 301 stainless steel for our springs. Our stainless steels typically contain 16% to 18% chromium, an element that forms a protective layer in passivation anyway. These percentages are comparable to various other stainless steel grades specified in the ASTM A666 Specification for Austenitic Stainless Steels. This chromium content provides corrosion protection in most non-extreme environments.
In summary, specifications sometimes require passivation to prevent corrosion, even after proper material selection; however, the acids and chemicals used in cleaning stainless steel for passivation can severely damage constant force, power, and constant torque springs . Choosing a different alloy (this is where our Qianye Precision Engineers can help!) may invalidate any passivation needs. Not all springs are susceptible to damage from the passivation process (such as open helical compression springs, bar and wire), but there are still some risks and added costs, so we recommend avoiding passivation altogether.
Shenzhen Qianye Precision Metal Co., Ltd. was established in 2006, supplying high-quality stainless steel springs for many fields. Through continuous efforts, it has obtained 19 patent certificates and 4 spring equipment software copyrights granted by the State Intellectual Property Office, creating an enviable industry influence. The company designs and manufactures a wide range of power springs, constant force springs, constant torsion springs, variable force springs and motor brush springs. Chiba works closely with customers to develop custom solutions to meet their individual needs. In order to provide better service, it has been continuously investing in production technology and supply chain. The company itself is a stainless steel raw material manufacturer. Due to the support of raw materials, there is no material limitation when making spring products; special material requirements can be developed and manufactured; in addition, the delivery time is greatly shortened. Quality is the top priority. Qianye has passed ISO9001, ISO14001 and national high-tech enterprise certification, and attaches great importance to the training of employees. Its spirit is “treat people with sincerity, create things with sincerity”, and strive for excellence.
