letter 47082

Need to keep an ungalvanized area on parts  

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Dear Sir/Madam
I am working for Spanish Solar System Supplier at the moment.There are some parts.The people say that,"there souldn't be galvanizing here". I have painted these parts for obtaining ungalvanized parts. As I know that,polymer based materials are inreactive for HDG. However, I saw some parts were galvanized locally. How can I prevent this situation? Are there any special chemicals and/or materials for not coating? Can you suggest anything?

Thanks...

Kindly regards

Hakan Esen, Material Engineer(BSc.)     galvanizing plant manager Bursa, Turkey

I have tried for years to find something to "mask" galvanizing - without reliable success.

In hot rolled steel, where there is plenty of millscale present, its possible to paint with a solvent based paint, and this prevents the acid cleaning the millscale. Where the steel isn't free of oxides, it doesn't galvanize. So where you paint, doesn't galvanize.
But this isn't 100% reliable.

Where the steel is very rusty, its a similar thing. Paint prevents cleaning which prevents galvanizing. Again NOT 100%.

Where the steel is not rusty and has no millscale (like fresh cold rolled for example), its nearly impossible.

There are a whole range of proprietry branded masking systems. I have not found a reliable one.

If you find a reliable technique, let us all know!!

Geoff Crowley    galvanizing &    powder coating shop Glasgow, Scotland

 

I don't know but copper plating works fine as a stop-off barrier in carburizing. Maybe someone else knows if it works as masking for galvanization too.

Guillermo Marrufo
Monterrey, NL, Mexico

Sirs:
Copper plating does not work.
The information on masking that you seek is on pages 91-94 in: "INTERGALVA 76" Edited Proceedings 11th International Galvanizing Conference, Madrid 1976, Edited by the Zinc Development Association, 34 Berkeley Square, London W1X 6AJ, Published by PORTCULLIS PRESS LTD., Queensway House, 2 Queensway, Redhill, Surrey RH1 1QS.
Likely you can get a copy of this article from the Zinc Development Association or by interlibrary loan from a large, or university library.
Regards,

Dr. Thomas H. Cook, Galvanizing Consultant Hot Springs, South Dakota, USA