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Prepping 3.5" galvanized pipe for Mig welding

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Prepping 3.5" galvanized pipe for Mig welding

Postby TDubs » Sun Dec 10, 2017 7:27 pm

Hi Folks,

I'm building a stand that will use a single piece of pipe as the main vertical support. Unfortunately, the only thing that I have is a length of 3.5" galvanized pipe with a .18" wall. It is strong enough for what I need but the galvanized coating has me concerned.

I've read about the problems welding galvanized and possibly getting ill from the process. So, I'm thinking about adding some muriatic acid to water in a plastic tank in order to clean off the galvanized coating. After soaking, I would give it a rinse in water with baking soda in order to neutralize the acid.

My question is: Will this remove the galvanization to the point where I could mig it to some clean hot rolled plate with .030" wire and gas? Or am I better off using flux core? I have a stick welder too but I'm not as proficient on that yet.

I'm open to any ideas.

Thanks,
Terry

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Re: Prepping 3.5" galvanized pipe for Mig welding

Postby LtBadd » Sun Dec 10, 2017 8:10 pm

You could use a grinder to clean off the gal, a google search of "will muriatic acid remove galvanized coating" will answer your question
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Re: Prepping 3.5" galvanized pipe for Mig welding

Postby TDubs » Sun Dec 10, 2017 10:40 pm

Thanks Richard,

A grindin' I will go. I found an extra coarse Scotch-Brite type pad for a 4.5" grinder at a local hardware store today. I'm going to give that a shot as there's a You Tuber stating that this is a good way to clean off mill slag from hot roll. I wonder if it will take off gal too. Otherwise, I have plenty of flappers laying around.

Thanks again,
Terry

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Re: Prepping 3.5" galvanized pipe for Mig welding

Postby Farmwelding » Sun Dec 10, 2017 11:20 pm

Grinder is all I've ever used. Works like a champ. Never had porosity from welding on it after grinding
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Re: Prepping 3.5" galvanized pipe for Mig welding

Postby TDubs » Mon Dec 11, 2017 1:08 am

I used the scotch-brite type pad. 10 minutes later, it's all clean and ready. So I should be able to just mig it now that all of the gal is off, right?

Thanks again!
Terry

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Re: Prepping 3.5" galvanized pipe for Mig welding

Postby cj737 » Mon Dec 11, 2017 8:42 am

Make sure the interior of that pipe is clean of galvanizing too...
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Re: Prepping 3.5" galvanized pipe for Mig welding

Postby LtBadd » Mon Dec 11, 2017 1:33 pm

TDubs wrote:I used the scotch-brite type pad. 10 minutes later, it's all clean and ready. So I should be able to just mig it now that all of the gal is off, right?

Thanks again!

Let us know how it welds, to my limited experience with galvanizing it seems scotch brite would not be enough to remove it, but I'm just thinking out loud. :o
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Re: Prepping 3.5" galvanized pipe for Mig welding

Postby TDubs » Mon Dec 11, 2017 10:01 pm

The scotch brite grinder wheel worked. It's a Black & Decker product but I think that Gator makes it. They look the same and other than the print on the B&D package card, they're the same size, etc. I also used a 2" wire wheel on the grinder to clean out the first 2" on the inside of each end. I then mig'ed a plate to one end of the pipe without any problems. I used .030" wire with Stargon mix gas without issue. I would have used .35 if I had some on hand but that was not the case. Either way, it's a strong weld and by the discoloration on the back of the plate, it loos like I have some decent penetration too.

Now for the extra plus side. I welded this several hours ago and so far feel fine. I.E., no symptoms of having breathed in any gal gasses.

I have two more welds to do on the pipe then the project will be complete. So far so good. Thanks for the help guys!
Terry

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Re: Prepping 3.5" galvanized pipe for Mig welding

Postby weldin mike 27 » Tue Dec 12, 2017 2:47 am

The process of removal and end result generally depends on how the galvanising (which is in fact zinc plating, galvanising is the term for coating something completely) was done in the first place. Gal stock like tubes,pipes and square tubes are done that way from the factory, inside and out with a thin even coating.
In some cases, in Australia at least, this coating is designed to be thin enough to weld with no preparation. (safety gear still required).
Post fabrication galivanising or hot dipping is done to raw steel after fabrication and is usually very thick and can be of random thicknesses. This must be removed before welding due the thickness and is hard to do. A trick is to watch for the sparks. Once you start to see them you know you are getting to the steel under the coating.

Another way to get it off is with an oxy torch. Heat the area you need to remove and watch it melt, then brush with a wire brush to scrape away the melted zinc. Works a treat on hot dipped threads and fittings but its messy.
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