Acid to remove galvanising?

[Welderpaul]

Scraping the barrel for ideas now i think, does anyone know of an acid that will eat off hot dip galvanising?

It's looking like we are going to be grinding off galv from the top flanges of around 12T of beams otherwise

Ta

 

[chunkolini]

I removed some galv with citric acid once.
A long time ago, but have a vague memory of trying this.
it may be one of those wrong memories but does ring a faint bell.

 

[atomant48]

The acid pickle in my zinc plating kit takes it off I think. Will look up the data sheet later to see what it is (maybe Google might say?)

 

[brightspark]

burn it off

 

[optima21]

hydrochloric acid should work at dissolving the zinc and may also work as a pickle for the steel.

just be careful that its in a ventilated area due to the hydrogen given off

 

[Welderpaul]

Were taking it off the top flange only from beams so can't burn it off. Watched a couple of you tube clips - hydrochloric acid looks nasty stuff.
We cant slosh it about to much, i don't want to get it on bits that are till to be kept galvd.

 

[rtbcomp]

It doesn't need to be concentrated. Zinc is a very reactive metal so any dilute acid should shift it, IIRC there's a product called 'brick acid' that's another name for dilute hydrochloric acid.

Because zinc is so reactive it easily forms an oxide coat, so brush it bright with a wire brush, treat with acid and repeat until it's gone. It'll be tedious though.

You may be able to use PVC insulating tape and polythene to protect the parts you want to keep, but any splashed acid can be washed off with water

As mentioned, hydrogen is given off.

 

[Welderpaul]

Reckon it could be blasted off Rog?

 

[brightspark]

it would blast off verry easy and fast with a 90cfm comp, and a blast pot with a 6mm jet and up to .1,5mm copper slag grit .its if the job warrents the price to get one or hire

 

[rtbcomp]

Reckon it could be blasted off Rog?

As BS says - you'll need serious kit, but it would be quicker than faffing about with acid. That's a job I'd decline!

 

[Welderpaul]

On its way to you tomorrow Rog

90 CFM - that's road compressor size isnt it?

To be honest, i'd rather blast it off than risk one of my lads getting burnt with acid. Worth buying the kit, doing the job, then selling the gear on as a package.

So...road compressor, blast pot, hoses, blasting helmet, copper slag grit, an empty yard on a saturday... anything else?...
Hodge Clemco decent gear? Is the nozzle jobby part of the blast pot set up?

 

[julianf]

I splashed some sodium methoxide solution on a galvanised trailer once, and it marked it.

The methoxide was fairly weak in NaOH. I reckon if you put it on straight (or mixed in with some wall paper paste) it would do for it quickly, and controllably.

Be aware that caustic soda (naoh) is just as grim as the acids though - but you can buy it over the counter with ease (drain unblocker)

 

[rtbcomp]

If you can cut it into 4 foot lengths I'll have a go.

Hodge Clemco are reckoned to be the standard, Anglo-Scott abrasives are worth a look.

I suspect you order the nozzle separately, there's a range of sizes and types.

You'll need a breathing air filter and tear-off visor protectors, gloves.

 

[brightspark]

once u have the gear and used it u probably wouldnt want to part with it for future use

 

[Welderpaul]

Yeah, lots of times i've wished i'd had the gear - blasting contractors round here are a right royal set of primadonas.

About 3-4K set up i reckon....

 

[brightspark]

a 150cfm pump would be nice and u can up the nozzle size for larger jobs

 

[rtbcomp]

Worth asking Hodge Clemco about reconditioned pots.

 

[Welderpaul]

Ebays probably as good a place as anywhere...buyer beware of course.

There's a few second hand pots that look ok.

So, road compressor, air hose from it to the blast pot, some sort of regulator on the side?, dump the media in the top, nozzle/dead mans handle on a hose from the pot, off you go?

Must quickly wear the hose from the blast pot to the nozzle?

 

[brightspark]

Ebays probably as good a place as anywhere...buyer beware of course.

There's a few second hand pots that look ok.

So, road compressor, air hose from it to the blast pot, some sort of regulator on the side?, dump the media in the top, nozzle/dead mans handle on a hose from the pot, off you go?

Must quickly wear the hose from the blast pot to the nozzle?

a decent new blast hose lasts a fair good while so does the jet

 

[rtbcomp]

That's about it.

The hoses last a surprising long time. Keep it as straight as you can, most wear occurs at bends.