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De-Galvanizing Parts Before Welding

CalgaryPT

Well-Known Member
Vendor
Premium Member
#1
I'm sure this is old news to professional weldors, and after 30 years of hobby welding I'm ashamed to say I just learned this now. But I recently repainted an old fire hydrant to mount in our backyard for our new puppy. I needed a way to mount it but didn't want to pour a concrete base.

So instead I plasma cut a 1/4" base flange, bought a 24" x 24" patio paver, and mounted some bolts I had to the flange after cutting off the heads (I need them to mount flat). Normally I'd just grind the zinc off prior to welding, but this wouldn't work well in this application.

Dr Google pointed me in a few directions, including commercial products. But the two solutions that I tried first worked great. The first was standard muriatic acid from Home Depot. The second was household vinegar.

Both worked, but what I learned was the muriatic (HCL) acid works too fast—if you don't watch it closely it will pitt and destroy the whole part. Regular vinegar is great, but too slow. Pickling vinegar (at the higher 7% acetic acid concentration) is perfect. In about 30 mins all the zinc was gone and the bolts were ready to weld. Best of all the stuff is cheap. Kind of fun to watch it bubble too ;)

Remember to wash off well with water prior to welding.

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#3
You can warm up the vinegar too, to make it work faster. When I can't get bare metal nuts and bolts from my supplier, I dump the plated ones in vinegar. Takes the plating off nicely and is WAY nicer to use than the Muriatic!
As a side note, I got a really good $ on some 1/4 rod rod years ago. Only thing was is was rusty as hell. I wasn't about to wire wheel all of it. So I got an 11' section of 4" pvc pipe and two end caps. Put the 10' rods in and added a liter of Muriatic acid. Roll, roll,roll. Dump the acid and fill with water and baking soda to neutralize. Roll, roll, roll. Done. Dump and wipe dry the rods. Easy peesy.
 

Janger

(John)
Administrator
Premium Member
#4
How do you go the other way? i.e. zinc plate something. I was googling. Various ways - dip in molten zinc 787F / 420C so not too hot - where do you get zinc? (Maybe passive cathodic protection sacrificial anode bars. again where and not costing the earth)
Electrolytic processes.... Seem to use some toxic stuff like muriatic acid again. Anybody done anything like these ideas or something else here?

Sugar and cats:


 
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CalgaryPT

Well-Known Member
Vendor
Premium Member
#5
Loctite SF7693 - Cold Galvanizing Compound (Zinc Rich) Part #82039. Calgary Fasteners etc.

It's galvanizing in a spray can.