Acid Dipping ( or treatment ) of Galvanized Structures

[BJC]

I am not a reqular reader of this group but I think it would be the place to get good input.
I have recently run into a requirment for acid dipping a galvanized structure to take the "Shine" off the structure and make it dull.
The acid would be acetic.

Is it common to dip galvanized steel into an acid bath?
What does it do?
I think the difference between acid dipped and undipped steel would be about 6 months. Since the structures have arrived on site they have gotten noticeablly duller. I have worked with lots of galvanized structures but as far as I know none of them were acid dipped.

Thank you for taking the time to read this.
BJC

 

[dik]

Over time, galvanizing normally develops a dull patina... Dipping the galvanized objects in a mild acid will hasten the process at the cost of reducing the protection.

Dik

 

[CoryPad]

The acid pits the surface (by selective dissolution). This pitted surface is rougher, which reduces the reflectivity.

You could try galvannealed steel instead of galvanized steel. Galvannealed steel is dull.


Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[swall]

Galvanized steel frequently has a light oil applied to retard the formation of "white rust" during shipping and storage. If you cleaned this oil off, the structure would develop the desired patina much sooner and perhaps the expense of the acid dipping could be eliminated.

 

[BJC]

dik, CoryPad and swall
Thank you for your prompt reply. Your answers cofirm my observations and suspicions.
The steel is about 5 miles from the ocean. Scince I started this tread it had gotten noticeable duller.
thanks again.
BJC