Nuts & Bolts newsletter 1/08 Passivation: no exposed iron/steel particles on surface - not a magic potion but a process that grants passivity are in reality only removing iron/ steel particles

News from NHML

Passivation By Fred Hochgraf

April 2, 2008

There is a host of people that wants to believe that passivation is some sort of magic film that enhances the resistance to rust spots on all sorts of corrosion resistant metals. But life doesn't work that way. A passivated metal is one that has no exposed iron/steel particles on its surface. So the magic potions that grant passivity are in reality only removing iron/steel particles.

Loose particles can be blown or wiped away.

Embedded particles originate from contaminated cutting fluids, contaminated grinding wheels, exposure to dirty environments followed by pressing, squeezing, rolling or drawing, wear particles shed by inappropriately chosen tooling, and contaminated media in abrasive cleaning machines. With embedded particles passivation can never be successful.

So successful passivation involves separate cutting fluids and abrasive cleaning systems for each alloy system, metic-ulous housekeeping, and a well informed work force.

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