Precision - stainless steel packed with all metal and atmospheric oxygen for reaction, the formation of oxide film on the surface. Unfortunately, the iron oxide in the form of ordinary carbon steel on oxidation, rust continues to expand, eventually forming holes. You can use paint or oxidation-resistant metal (for example, zinc, nickel and chromium) plating to ensure the carbon steel surface, but, as everyone knows, this protection is only a thin film. So the magnet is not up.