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300 vs 400 Passivation

Do both 300 and 400, specifically 420, series SS require passivation? Which one is more corrosion resistant?

Ted Browning
- Shakopee, Minnesota
2001

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No stainless steels absolutely "require" chemical passivation treatment. Now, whether your parts "should" be passivated to resist corrosion in service or processing is another matter. The 300 and 400 series alloys will generally benefit from chemical passivation, i.e., will be more resistant to corrosion. Whether the difference in corrosion resistance before and after passivation will be significant depends on how the components are processed (e.g. welded, etched, etc.) and the nature of the service conditions. In most environments, the 300 series alloys (304 and 316 are most common) are more corrosion resistant than the 400 series alloys (including 420).

Hope this helps.

Larry Hanke
Minneapolis, Minnesota
2001