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Removing zinc plating (for welding bodgery)?

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Eric The Viking

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I'm knocking up a gallows bracket for SWMBO...

... for a hanging flower basket (what did you think I meant?).

I'm using some scraps of rebar - I could just about get it hot enough to bend with a Mapp gas blowlamp, so I've made the hook for the end. So far, so good, but I want to weld on some square plate washers, which will be drilled to take screws to attach the metal to the wooden plate for the wall.

Unfortunately my Square washers are BZP, so I was wondering if there is an elegant way of removing the plating for welding. Obviously I could just have at them with the grinder, but I'd rather keep them as flat and smooth as possible. Could I, for example, remove it with reasonably conc. hydrochloric acid? I have some "brick acid" available.

This can't be an uncommon nuisance so I was wondering what people usually do, apart from just holding their breath or wearing a facemask.

Cheers, E.

PS: this is definitely a "made from scraps" job. Black Hammerite hides a multitude of sins (and welding spatter), and it's functional rather than blacksmith-quality pretty...
 

Just4Fun

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If you are going to smother it in Hammerite I would expect that to hide any imperfections caused by the use of a grinder.
 

marcros

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I needed to remove the zinc from some bolts, so that the blacksmith could reshape the heads for me. A couple of hours in vinegar sorted them.
 

MJP

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Hit the washers with your MAPP gas - get them red hot, the Zinc burns away to a yellow dust which wipes off.
All over in seconds.
Martin.
 

marcros

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isn't zinc oxide one of the nasties that you don't want to be breathing in?
 

Trevanion

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MJP":2au9ne5x said:
Hit the washers with your MAPP gas - get them red hot, the Zinc burns away to a yellow dust which wipes off.
All over in seconds.
Possibly the worst way to do it, the fumes coming off burning zinc is an extreme health hazard. It's the fastest way to get Metal fume fever besides welding the stuff. I've personally been mildly sick from welding Zinc coated nuts onto the top of sash weights and It's not something I wish on anyone as it's a horrible feeling in your throat and you don't sleep right at all.

I've found battery acid works quite well so I imagine Hydrochloric would work fine, just keep an eye on it so you don't start eating the steel too much. Also make sure to neutralise the acid.
 

Rorschach

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Don't use hydrochloric, you will never stop them rusting afterwards.
 

Eric The Viking

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Thanks everyone.

I had quite forgotten I have a half bottle of once-glacial Acetic acid, glass stopper'n'all (yup it got wet!). So, given the warnings regarding HCL, I'll try that first and see how I get on. After all, it only attracts seagulls*...

It's all very well making something from scraps, but by the time you finish, you might just as well have bought something from an agricultural supplier (or similar).

E.

*Anyone who has lived in a small seaside town will understand. In my youth, Burnham-on-Sea had only two chip shops, one at each end of the High St. You could instantly spot the tourists as they were the ones (stupidly) looking upwards when they came out. Locals: duck, cover, run. Much like Cheddar, but with added precision bombing.

But I digress...
 

Eric The Viking

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Update: the acetic acid (diluted roughly 50:50 from whatever it was in the bottle) is slowly removing the zinc, leaving a dark grey/black surface. I've left it in a clear ice cream tub in the sunshine (warmth might help). So probably a success.

Shame about my welding though - good if Swiss cheese is what you're after. But Hammerite, etc...

:oops:

E.
 

Just4Fun

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Eric The Viking":2jz6nh7j said:
Shame about my welding though - good if Swiss cheese is what you're after.
I did a welding course years ago and the instructor said my welding was like an old woman's fart: rough and strong :roll:
 

TFrench

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I just use a flap disc in a grinder

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MJP

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Trevanion":1k38idgs said:
MJP":1k38idgs said:
Hit the washers with your MAPP gas - get them red hot, the Zinc burns away to a yellow dust which wipes off.
All over in seconds.
Possibly the worst way to do it, the fumes coming off burning zinc is an extreme health hazard. It's the fastest way to get Metal fume fever besides welding the stuff. I've personally been mildly sick from welding Zinc coated nuts onto the top of sash weights and It's not something I wish on anyone as it's a horrible feeling in your throat and you don't sleep right at all.

Aw come on - we're talking about heating a couple of washers here, not welding up the Forth Bridge!
I've twice built 30ft radio towers from galv piping, just welded through the zinc - got Zinc Flu the first time, took more care the second time. But a couple of washers? No way.
Martin.
 
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