Everything you need to know about the Stainless Steel Passivation Process? For metal workpieces made of stainless steel and other metals, passivation is a finishing procedure. It is a chemical process that does not use electricity that produces an outer layer of shield material and uses nitric or citric acid to remove free iron from the surface. As a result, stainless steel components exhibit superior corrosion resistance since they are less likely to react with air. The Stainless Steel Passivation Process results in a thicker chromium oxide layer and dramatically increased corrosion resistance since it removes free iron and increases the metal's chromium content.
Why are certain grades of stainless steel passivated?
Stainless steel has strong inherent resistance to corrosion. It is not completely impervious to corrosion, particularly rust. The high chromium content in the alloy gives stainless steel its superior corrosion resistance. The surface of stainless steel develops a thin coating of chromium oxide as a result of the chemical reaction between chromium and oxygen. Small regions of the surface could still rust despite the oxide layer because grain boundaries or foreign objects in such locations can cause some iron to be oxidised by water molecules. Rouging is the name of this procedure. Passivation is the term for the elimination of impurities and the process of oxide development.
What happens during passivation?
Depending on the various standards, there are several further requirements for the passivation of steel and other metals. Most passivation standards share the following steps, which are:
- The steel is cleaned to remove iron and extraneous contaminants.
- Through immersion, the workpiece receives chemical treatment. This process is completed in the nitric or citric acid bath.
- To determine if the chemical treatment was successful or not, the stainless steel surface is evaluated.
The natural process, which happens when the material is exposed to atmospheric oxygen, is sped up by the passivation process. Therefore, passivation aids in the quicker formation of the inert oxide layer. Additionally, the protective layer that has accumulated becomes noticeably thicker than what is observed in nature.
The following processes are performed daily for all the various passivation criteria, as was already indicated. Cleaning the workpiece is the first step in the passivation process. The steel needs to be spotless and free of any impurities.
This situation is demonstrated via a validation test. All of the components are then submerged in an acidic passivation bath following cleaning. One of these methods, nitric acid passivation, nitric acid with sodium dichromate passivation, or citric acid passivation, can be utilised, depending on the grade of stainless steel. The temperature ranges from ambient to 60° C, and the time length, which is typically at least 20 to 30 minutes, is predetermined.
The components are then neutralised using an aqueous sodium hydroxide bath. The stainless steel object is then dried after being cleaned with clean water. To validate the passivation findings, the surface is put through a testing procedure using humidity, high temperature, or salt spray. But since passivating martensitic stainless steel is difficult, it needs careful handling.
Therefore, select Reba Safer Chemical for Citric Acid Passivation to prevent corrosion on your equipment. You have come to the right place if you need any information on Rust Removal from Stainless Steel. We'll help you with this and walk you through the procedure.
