[TheForge] Hydrochloric acid and galvanising

Sat Jul 19 08:11:00 2003

Years ago we had a wood stove in the kitchen, and used galvanized stove pipe
for the exhaust.  We would have liked to use black, but had this available,
so used it.  While it was hot, we put some vinegar on it and that turned it
black.  Did a real nice job.

Rick Crawford at Rafter Lazy C
Home of Rick's Forge and LEM the Wonder Mule
In the middle of Northern Illinois
http://www.rafterlazyc.com
[email protected]

----- Original Message ----- 
From: "Bruce Freeman" <[email protected]>
To: <[email protected]>
Sent: Friday, July 18, 2003 11:10 AM
Subject: Re: [TheForge] Hydrochloric acid and galvanising

> I strongly doubt that PURE hydrochloric acid would make galvanized turn
> black.  What else have you had in this acid?
>
> If you pickle the zinc off the steel, the steel should be shiny, not
> black.  I think you've left something behind, but I don't know what.
>
> Black is often due to finely divided metal.  I'm wondering whether you
> may be precipitating out some less-active metal on the surface of your
> galvanized steel.  If this is the case, no telling how stable it would
> be.  Finely divided metal could be loose as a powder.  Even if not
> loose, it would react with air fairly readily.  So, I doubt this would
> be a stable color.
>
> Zinc and other metals can be turned black by sulfide - but you won't
> find sulfide in hydrochloric acid.
>
> Don't know whether this helps.
>
> Bruce
> NJ
>
> >>> [email protected] 07/17/03 11:23PM >>>
> Does anyone know if the blackend look adding H Ch acid to galved steel
> is as
> durable to corrosion as plain galv? whats the reaction that makes it
> go
> black? have I even got the right acid, I did this a long time ago and
> havent
> used it since. Does it actually react or just remove the galv and show
> black
> steel?