Metal finishing Q&As since 1989

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White stain/spot on annealed silicon steel

Dear Sir,

Recently, we found some white stain/spot on the annealed silicon steel. SEM results showed that these stains are not white rust based on their oxygen content.

We do not understand how these white stain/spots are being formed. Will they affect the lifespan of the silicon steel.

please enlighten us.

Thank you

Shirzaw
Manufacturing - Singapore
2005

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2005

Well, you have to give a more detailed description on what you did before the spots appear. To little information for any practical idea on what it is.

Did you did polishing before that? Or just annealed the entire steel billet/ingot?

Did you send it through a die-casting process?

How big are the spots?

Steel rust is brown, what do you mean by white rust?

I need to know the data above because there are a ton of reasons why the spots will appear, from manufacturer of the steel to the process of treatment of the metal.

We have a same problem too here, but our problem is with aluminium die-casted products, where micro-sized dots appear all over a polished surface over 50 x magnification. Further more, eye-visible white dots appear on the surface too.

Yong Tze Shoong
- Kawasan Perindustrial Pasir Gudang, Johor, Malaysia