Removing Galvanizing Discussion

[SIGNGUY]

I thought I'd bring up the Galvanizing discussion once again as I have recently had to remove Powdercoaters and ran into some old issues again and am working at fixing them.. The issue is with powdercoating over galvanizing and getting what is called outgassing.. causes small bubbles in the finish.

My old guy would sandblast, bake the tubs to remove the "gasses" and then powder and rebake... and 90% of the time they came out great.

My new guy tried the same process and got terrible results, he suggested I try to remove the galvanizing myself as they where not set up for doing that ..

I have found the sandblasting it off, takes FOREVER and Can cause warping of the metal

I have tried Vinager and nothing happened, I tried Aluminum Brightner as I was told that would work, only to remove some but would loose effectiveness very fast and didn't work well.

then there is good ol Muratic Acid, which works great, but you have to be very careful due to the fumes, and of course getting it on you, but the problem I have with that is I don't have a tub to dunk the big tubs in, and haven'et tried to spray it on yet?

Just curious as to what you guys are doing ,what you guys have run into, or have done...

[collecture]

Have you tried any sort of paint stripper?

[tkaz]

There was a discussion on using molasses a while back, not sure how far into the metal it gets, but VMC81 had done a couple of shelves and they looked decent:

http://soda-machines.com/discussions/index.php/topic,10328.0.html

There was also another thread on a chemical stripper from Autozone, but I can't seem to find that one around, looked like it did a nice job  on shelves from what I remember.

[Eric]

Can you take the tubs to the folks that do your zinc plating... parts are run through an acid bath first... just have the guy strip/run it through the bath .... that'll should take care of the galvanized coating... but get it cleaned (acid washed off completly) then coated.

[collecture]

There was a discussion on using molasses a while back, not sure how far into the metal it gets, but VMC81 had done a couple of shelves and they looked decent.

Even soaking in molasses & horse feed, you would still need a large enough tub to submerge it in.

Can you take the tubs to the folks that do your zinc plating... parts are run through an acid bath first... just have the guy strip/run it through the bath .... that'll should take care of the galvanized coating... but get it cleaned (acid washed off completly) then coated.

The zinc plater I used to use couldn't have galvanizing in their system. I think it varies from place to place.

[SIGNGUY]

I used to get the tubs zinc plated before ever trying to powdercoat.. problem again is the size.. plus my zinc plater is 2 hours away and now I just send him all my small stuff, as most of the large items I now powder.. and yes, he was hesitant to dip galvanized in his acid bath and , he required a whole seperate bath and of course a larger charge....
I have no problem using Muratic as it works great and quick , just can't breath around it and have to do it outside... but that only works for the small stuff, not sure on the tub yet ,... will have to experiment.

I am kinda curious as to what you other restorers are doing that powder coat your tubs? and have you experienced this outgassing effect and how have you worked around it?

[johnnyselman]

With the aluminum brightener the parts realy need to be sumerged. Yes  it will weaken but will still eat the parts clean if you have patience. I like to put the parts in to soak while working on other stuff. Check ever now and then to see how its coming and to move the parts around. I find if parts are stacked up some areas are slower to come off.I did my 110 (not the tub) with 2-3 gallons. Make sure the parts aren't real dirty as that just weakens the brightener sooner.
 The trick is to get the parts rinsed and dried before they flash rush. Of course a quick sand blasting afterward would take care of that.The shelfs below were stripped, rinsed in hot water and dried quickly but not blasted.
  
 As for the tub you may try Easy-Off (the original) oven cleaner . I have never tried it on galvanize but have used it many times on Anodized aluminum . It has Lye in it.

[SIGNGUY]

so those shelves where cleaned with Aluminum Brightner? how long do you think they where submerged.. I guess I only tried a bit.. originally just sprayed it on to no avail.. do you put it in straight or dilute it?
thanks for the input,, I'll check on ez off oven as ell for the tub... just trying to find an easy way.. saves me labor expense from my powder coater...

[johnieG]

I've always used Metal prep ( Phosphoric acid) you still need a rubber gloves & a respirator, but it doesn't fume as bad a muratic acid.  I've had entire ice-chests dipped at a local re-galvanizer who strips highway  metal guardrails & then re-dips then in hot zinc for the state of Michigan, nice big tank, it it goes. it comes out nice clean steel, sans the zinc.  you can also check if there is a Redi-strip dealer around your area, they use an alkali/ electro stripping process that will eat rust & zinc off of steel & not touch so much as 1 gram of base Iron in the process.

[johnnyselman]

so those shelves where cleaned with Aluminum Brightner? how long do you think they where submerged.. I guess I only tried a bit.. originally just sprayed it on to no avail.. do you put it in straight or dilute it?
thanks for the input,, I'll check on ez off oven as ell for the tub... just trying to find an easy way.. saves me labor expense from my powder coater...

Yep! just Aluminum brightener. Time varies.On these I put then in at 7 am, went to work and when I got home at 12 for lunch they were done.The A/B was fairly used so I knew it would take a while. I would say with new A/B and parts not stacked together probably a hour or less would do. I do find that some parts seem to have alot thicker galvanizing than others. I like to use it nondiluted but sometimes add water to get sometime submerged. Sometimes on long stuff I have to dip end at a time, but the stripped end will rust while the other is in. That rust will come right off by just puting it back in for a few seconds.
 I know this sounds like a lot of work but it realy isn't once you get a system down. I tried sand blasting but as you know its hard to tell when all the galvanizing is gone. I sometimes dip the part until clean then sandblast the flash rust off..