Official Answer
Answer
SAE 1070 carbon steel is the most economical choice for retaining rings but lacks inherent corrosion resistance. In high-humidity automotive applications (e.g., under-hood or suspension components), it will oxidize rapidly, forming iron oxide ($Fe_2O_3$), which leads to a reduction in the effective cross-section and premature failure. Common protection methods include zinc phosphate coating ('Oil and Phosphate') or zinc flake coating (e.g., Magni or Geomet). However, these coatings can add thickness, potentially interfering with groove fit. If the application involves salt spray, the transition to 302 stainless or 17-7PH is usually necessary to ensure the 10-15 year service life required by modern OEMs.
