Why Do Stainless Steel IP Enclosures Develop Premature Rust Spots?
When brown spots appear on the surface of stainless steel IP enclosures a few months after installation, it is often assumed that this is due to the material grade. However, based on nearly two decades of custom fabrication experience, Supro has found that over 90% of premature rusting incidents can be attributed to four preventable factors: free iron contamination during cutting or grinding, thermal discoloration from unshielded welding, crevice designs that trap electrolytes, and the omission of passivation treatment. Although the passivation layer on the surface of 304 or 316 stainless steel is robust, it cannot compensate for embedded particles or heat-affected zones with insufficient chromium content. To ensure that stainless steel IP-rated enclosures achieve their intended performance, the entire manufacturing process must be strictly controlled, from dedicated tooling to post-weld acid pickling. This article analyzes each root cause from a manufacturer’s perspective, providing purchasers and engineers with actionable criteria to distinguish genuine metal defects from premature corrosion caused by […]
Why Do Stainless Steel IP Enclosures Develop Premature Rust Spots? Read More »


























