[sdiy] products for rust removal - the joys of phosphoric acid

[aankrom]

It has to be phosphoric acid. It's better at longterm rust-removal and 
is far less fumy. Plus, when dealing with galvanized steel, HCl would 
not give me that great zinc phosphate finish. A layer of zinc phosphate 
looks great AND it improves paint adhesion to galvanized steel. I wonder 
if zinc phosphate gets rid of rust? You can use a zinc phosphate 
solution on galvanized steel. It's acidic enough to react with the zinc. 
But I'm interested in stuff I can get at a place like a hardware store.

I think I might research using diluted Naval Jelly too.

Don't get me wrong. HCl is great to get rust off of regular steel. I 
use it on tools all the time.

AA

On Thu, 22 Dec 2011 15:53:08 -0800, James Hughes wrote:
> If you cant find phosphoric, you can use hydrochloric. Its sold in
> most big home improvement stores as muriatic acid. Its commonly used
> for cleaning brick work and lots of other things.
>
> Concentration from Wikipedia:
>  -- Pickling of steel --
> One of the most important applications of hydrochloric acid is in the
> pickling of steel, to remove rust or iron oxide scale from iron or
> steel before subsequent processing, such as extrusion, rolling,
> galvanizing, and other techniques.[5][17] Technical quality HCl at
> typically 18% concentration is the most commonly used pickling agent
> for the pickling of carbon steel grades.
>
> On Thursday, December 22, 2011, aankrom  wrote:
>> I used to able to find this cheap-ass toilet bowl cleaner that used
> phosphoric acid. While being a lousy toilet bowl cleaner, it was a
> great rust remover. Plus I noticed that when I soaked a rust
> bespeckled galvanized chassis, the phosphoric acid would react with
> the zinc, giving the WHOLE chassis this nice battleship-grey finish.
> You couldnt even tell the rust had been there unless it was really
> pitted. But I cant find it anymore. I suppose its a combination of 
> the
> the toilet bowl cleaner being lousy at its job and the fact that
> phosphoric acid can contribute to algal blooms and such. So I
> rediscovered Naval Jelly and the hassles that come with it. It works
> fine on bare metal rusty surfaces. But it eats paint and sometimes
> leaves this residue thats as much of a pain to get off as the rust. I
> should try pouring a glob into a tub of water and try my galvanized
> chassis soak. Maybe diluting it is the answer.
>  > The effect phosphoric acid has on galvanized steel is similar to a
> technique to treat metals on motorcycles and such called 
> "Gibsonizing"
> but try to Google THAT and get hits pertaining rust-removal. 
> Seriously
> - even you try gibsonizing+rust+zinc, etc.
>  >
>> I was wondering if anyone else had some tips for products that
> remove rust. Ones that are stronger than citric acid. Something like
> Naval Jelly is a plus.
>>
>> Anthony
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