![]() Stainless steels also contain varying amounts of carbon, silicon, and manganese. Increasing the amount of chromium increases resistance to corrosion. But passivation occurs only if the proportion of chromium is high enough and oxygen is present. Stainless steel contains enough chromium to undergo passivation by forming an inert film of chromium oxide on its surface. This iron oxide film (rust) is “active” and accelerates corrosion by making it easier for more iron oxide to form. Unprotected carbon steel rusts when exposed to air and moisture. Stainless differs from carbon steel by the amount of chromium present. This is why passivation is the final step in stainless steel parts manufacturing. It’s not uncommon for the passive oxide layer of stainless steel to sustain damage through any number of mechanical, industrial, and environmental processes. In stainless steel it typically takes 24 to 48 hours to achieve a uniform and stable passive layer, but passivation can occur only in certain conditions. It begins immediately after surface contaminants are completely removed. Passivation is an essential process in the manufacture and quality assurance of varying grades of stainless steel. Chromium produces a thin layer of oxide on the surface of the steel-the “passive” layer-that prevents surface corrosion. ![]() Stainless steel is an alloy of iron with a minimum of 10.5 percent chromium. What makes stainless steel stainless? In a word, chrome. In chemistry and engineering, passivation refers to a material becoming passive, or less affected by the environment. Rust is bad for business, which is why passivation is essential. ![]() For customers, it can mean headaches and expensive delays. Yet it’s not unusual for fabricators to complain about the appearance of rust after commissioning or installing components. In the world of stainless steel fabrication, stainless steel should mean just that-stainless. An automated arm electrochemically cleans to ensure complete passivation occurs along a stainless steel weld joint.
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