Today, we are going to discuss the "Corrosion Control for SUS Products. A Note on Passivation Treatment (Passivate Treatment)I'll do the "I".
SUS corrosion is the result of oil and other metal contaminants that remain on the surface of SUS products when they are used as they are after processing. When electrolytic substances adhere to them, local batteries are formed due to the difference in ionization tendencies between the different metals, causing "electrolytic corrosion" and corrosion starting from the product surface.
To prevent corrosion of the product surface, an oxide film is formed. That is passivate treatmentThe company says it is called
In the following section, we will make a bulleted note of the basic characteristics of the passivate process that are necessary for the design.
What is passivate processing?
- Surface treatment of passive film on stainless steel
- The process changes the surface of the ingot, so there is little dimensional change. No change in hardness
- Purpose is to improve corrosion resistance (to prevent rusting)
- Thin, dense film formed on the surface layer of stainless steel when the chromium in stainless steel combines with oxygen
- Chromium oxide is a combination of chromium and oxygen in stainless steel, but is destroyed by chlorine and other substances.
- Possible pretreatments include electropolishing, pickling, and chemical polishing
*Not limited to stainless steel, if an oxide film is formed, it is called passive.
Passivate Processing Method
- Treatment with strong oxidizers such as nitric acid
- Heating method in an oxygen atmosphere x Caution because the product will be distorted
- Method of anodic polarization in acid solution
- Immersion treatment in an oxidizing agent can be done at lower temperatures and is more cost-effective
Examples of passivate processing
- Salt damage can be treated by pickling, electropolishing, and passivation for better corrosion resistance.
- Passivation treatment is performed to enhance reliability for use with various chemicals. (Pretreatment: Pickling)
- Electropolishing + passivation treatment is used to suppress metal elution and algae formation when used for pure water. (Pretreatment: Electropolishing)
That's it.
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