Welding on Galvanized / Coated Steel & Cleaning Steel

[Randy V]

Recently I embarked on a project to build a removable fence across my driveway.
Building bolt-down fence posts means welding galvanized steel posts to mild steel plates.
It's dangerous to weld on galvanized steel due to gasses emitted. Also, the welds are rarely clean and strong.
I found a trick though.
Muriatic Acid will immediately destroy any galvanized cladding in a matter of minutes.
Warning - do this outside and be careful of the vapors.
I just pour an inch or so of the muriatic acid in a plastic container, then drop the fence post in. 60 seconds later, pull the post out and rinse well with water.
Be aware that the steel will flash rust, so make sure you weld, then paint/prime quickly.
You can also use MA as a derusting bath for any ferrous metal.
MA has not proven itself to be destructive at all to steel. I have left some parts bathe in it for a month and all I got out of the container was perfectly clean steel.

Additional Caveats
Always wear hand and eye protection
Do NOT do this indoors.
Do NOT breathe the vapors as they are quite corrosive
Do NOT get it (MA) near any nonferrous metal as it will immediately start to consume it..
Photos below of fence project and various tests of Muriatic Acid
((Apologize that they are not in the right order))View attachment 116315

View attachment 116315

 

[Randy V]

Odd - it appears the photos double posted. I will attempt cleanup..

 

[Randy V]

 

[Randy V]

You can use White Vinegar to clean rusted steel also, but it will take weeks...

 

[Ron Earp]

Nice work, way to get things done!

Welding on galvanized stuff is crappy. I've had to do it a few times and always set up a big fan and worked upwind.

Just to let you know.....I can still see that RV

 

[Mike Pass]

Muriatic acid is actually hydrochroric acid. Note that if you need to dilute it the mixing gives out a lot of heat so be very careful and always pour the acid into the water and NOT water into acid as the heat can boil the water and spit acid in your face - not good!
Cheers
Mike

 

[PhillipM]

Citric acid will do it too, albeit slower. And much safer.

 

[JP Verweij]

I usualy just take out the grinder with a 60 grid sanding disk to take the galvanising off where I need to weld. Just a few seconds and go on with your welding. Spray some WD40 on the cherry red weld and it won't rust for a decade.
Galvanising is just a surface threatment.

 

[Randy V]

Muriatic acid is actually hydrochroric acid. Note that if you need to dilute it the mixing gives out a lot of heat so be very careful and always pour the acid into the water and NOT water into acid as the heat can boil the water and spit acid in your face - not good!
Cheers
Mike

Yeah, the stuff you get at the store costs about $5 a gallon and is already diluted heavily with only 30% being acid. It’s used to clean swimming pools..

 

[Randy V]

I usualy just take out the grinder with a 60 grid sanding disk to take the galvanising off where I need to weld. Just a few seconds and go on with your welding. Spray some WD40 on the cherry red weld and it won't rust for a decade.
Galvanising is just a surface threatment.

I did it for years the same way. You end up removing some of the metal in the process. If your tubing is only 1.5mm thick to begin with, that could be a structural problem.

 

[BenL]

Be careful how you clean up after using muratic acid, it will eat cement (it's useful for cleaning messy mortar from clay fired bricks)