Where to find hydrochloric acid?

**Pete F** · 27th October 2009, 10:13 PM

In a DVD by Covell he shows using muriatic acid to clean off zinc plating. I've often had small objects such as nuts and bolts I've wanted to tack on with a TIG and have been tediously grinding/sanding the plating off. Notwithstanding the cautions of using acid, a simple process of just stripping it all off would be perfect. I believe this is hydrochloric acid, is this freely available and if so from where? Is it as effective at cleaning metal before welding as the Covell DVD implies. If you haven't seen the DVD he simply dips the part in the acid then neutralises with water before drying and welding. Again, I appreciate the cautions of using strong acids having seen what sulphuric acid can do!

Pete

**Dengue** · 27th October 2009, 10:24 PM

Try any pool shop for a bottle of HCl. Used to release the chlorine molecule for keeping the bacteria down

regards,
Jill

**johnc** · 27th October 2009, 10:36 PM

Its sold in hardware stores as spirits of salts, anything from about 500ml to around 15 litres. Be careful with it though, it is highly corrosive to skin, eyes, tools, concrete, clothing etc etc. It really is a case of follow the instructions and use appropriate protective clothing, particularly to the eyes and hands, and exposed skin in general.

**Dengue** · 27th October 2009, 11:12 PM

And if diluting the acid, always add the acid to water, and NOT water to acid. And be very careful of splashes. It is surprising just how much splash you can get simply pouring the acid in to a bucket of water, so follow johnc's excellent advice about protective gear, especially around the eyes

Joill

**BobL** · 27th October 2009, 11:40 PM

At work we make extra highly concentrated (13.6 molar) HCl by dissolving pure HCl gas in chilled high purity water. The resulting acid produces a violent reaction when it contacts a metal like Zn and it instantly foams up like a CO2 fire extinguisher.

We also purify fuming grade (12 molar) HCl by distillation. This produces a small amount of residue which we normally discard so can access this if I want to. The residue is not full strength (~9 molar) because the distillation process drives off some of the HCl gas but it's still more than concentrated enough to dissolve the Zn off steel.

Just be aware that dissolving Zn plating happens very quickly (~10 minutes) so make sure you keep checking - if you walk alway and leave it you can come back to a pile of black sludge and have dissolve everything ie the Zn and Steel. Even with the HCl you buy at the hardware it will also foam up but not so quickly but it's still a good idea to place the container of HCl inside another container or tray so the foam doesn't leak out all over the place. I use a plastic lid from a plastic storage tub as a work tray.

**Claw Hama** · 28th October 2009, 07:06 AM

Pete, why not just buy black nuts & bolts etc?

PS I think Bummings sell Hydrochloric.

**Pete F** · 28th October 2009, 07:30 AM

Originally Posted by Claw Hama

Pete, why not just buy black nuts & bolts etc?

PS I think Bummings sell Hydrochloric.

It's difficult enough to buy metric nuts/bolts in this "metric" country of ours as it is

TIG requires perfectly clean surfaces anyway.

Thanks, sadly I'm off to Bunnings today (I loathe that place) so will try to get the acid there. I'm not sure what strength Covell was using in the DVD, I'll watch that part again this morning, but it was definitely quite an intense reaction!

Pete

**Dengue** · 28th October 2009, 08:35 AM

Why not call in at a pool shop and get a bottle of acid , rather than raise your blood pressure at Bunnings?

**Pete F** · 28th October 2009, 08:43 AM

Originally Posted by JillB

Why not call in at a pool shop and get a bottle of acid , rather than raise your blood pressure at Bunnings?

Unfortunately I have to go down there for some other things so will probably just grit my teeth and do two in the one hit

Thanks for the heads-up on the pool suppliers though, not having a pool I wouldn't have known.

Pete

**jatt** · 28th October 2009, 08:24 PM

From memory HCl is what brick cleaners use. Obviously a quick check of the label will confirm this in case I'm leading u astray.

**Skew ChiDAMN!!** · 28th October 2009, 08:58 PM

Yeah, our local Bunnies sells it.

But, AFAIC, JillB's on the right track. It was much cheaper to buy through our local pool supplier.

**scooter** · 28th October 2009, 09:06 PM

Originally Posted by jatt

From memory HCl is what brick cleaners use. Obviously a quick check of the label will confirm this in case I'm leading u astray.

'Tis correct.

Cheers.............Sean

**Pete F** · 28th October 2009, 09:22 PM

Yep got it at Bunnings today, no drama at all. Not sure if it's required to clean the piece additionally after the acid, I did as it seemed to still have a bit of a layer of "something" on it but it would be handy to not have to.

**pipeclay** · 29th October 2009, 06:02 PM

Buy your Hard to get Metric Items from an Engineering suppliers EASY.

**Pete F** · 29th October 2009, 06:55 PM

Originally Posted by pipeclay

Buy your Hard to get Metric Items from an Engineering suppliers EASY.

Ha ha, yeah right. Last time I bought a few metric bolts from the guy down the road he charged some outrageous amount each. I thought he was joking, but the joke was on me! It was almost worth a trip down to Coventry and they're hardly a 2 dollar shop either!

Lucky for me I get up to Singapore and Hong Kong regularly and often come back with a stack of metric nuts/bolts to restock my store

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