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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Hot dip Galvanisation of already electrogalvanised metal
September 26, 2012
Q. Hi,
I am about to buy some safari tents for a small tent lodge hotel that I am starting.
The frames of the tents have been electrogalvanised only.
The supplier is telling me that it is not suitable for the sea side region where my lodge will be located.
He is proposing to upgrade to stainless steel 304 but he is quoting US$3500 more. Not workable as per my budget.
I am thinking to apply a hot galvanisation bath onto the already electrogalvanised frames ... can I do that ?
If anyone can help me. Thanks. Julien
- Mauritius
A. Hi Julien;
Hot dip galvanized parts will last longer than electrogalvanized ones. But again it will require re-galvanization if any contact occurs with seawater. Moreover surface will have some white-rusty finish.
You can find a research in AGA's site about corrosion rates:
www.galvanizeit.org/about-hot-dip-galvanizing/how-long-does-hdg-last/in-the-atmosphere/service-life-time-to-first-maintenance/atmospheric-corrosion-data/#generalRates
You might also try painting with epoxy after hot dip galvanizing. It would be the best option and still cheaper than stainless steel.
- Ankara, TURKEY
September 27, 2012
A. "Electrogalvanizing" is a term that mostly creates confusion.
It often means zinc electroplated.
Corrosion protection using zinc is proportional to the thickness of the coating.
Electroplated might have typically 10 microns of zinc, hot dip galvanized might have 100 microns.
To Hot dip galv a previously electroplated item isn't really any problem. In the usual acid cleaning part of the HDG process, that thin electroplating will strip off in no time.
You could consider polyester powdercoating over the galvanizing. I think that would be better than epoxy, given that epoxy is UV sensitive.
Even powdercoated HDG will be cheaper than 304 stainless.
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
October 4, 2012
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