How can i weld galvanised steel?

Branden

I was 16yrs old doing my first big job with my Dad and a friend of his in Aspen,Co putting ice cutters on airplane hanger doors. My last job of the day was to take a torch and make cut outs for wheel clearance in the hanger doors that was made from galvanized metal. I hummed right thru the job, then hopped on my first air flight back to Denver. By the time I got there I was one sick puppy. The airline thought it was air sickness since it was my first time flying.

My Dad said he had just forgot to tell me about welding and cutting galvanized. Took several days to shake that one off but I sure learned something.

T_Bone

If you should decide on a carbon steel filler metal you will need to remove the zinc coating in the weld zone prior to joining. The zinc will also be destroyed in the HAZ (heat affected zone). The coating could be replaced in that case by using something similar to the regalvanizing bar on our web site or by metallising.

There's many different choices but for what your doing you might consider the carbon arc process using Everdur(silcone bronze) as a filler rod.

In this process a typical stick welding machine is used with the electrode negitive. A copper coated carbon rod(I suggest 3/16" dia.) is sharpen on one end to a point, then incerted in to the rod holder, then the filler rod(I suggest 1/8" dia.) is placed where you want the weld and layed almost flat, then the carbon rod is started on top of the filler rod holding a very close arc. It flows like butter and depending on your travel speed/amps the bead will be flat to very round.

This process is rated at 30,000psi tensil strength and low distortion. It's more like a solder but stronger and very weak as a structual weldment. We use the process for seal welding and it cleans well with a rag with no splatter and has a very fast welding time.

The carbon rod is sharpened to where the copper coating is removed for approx. 5/8" with the black carbon tip coming to a point.

The other choice would be again stick welding with 6010 used in straight polarity(DCSP). Yes this rod is used DCRP but I found it best welds on galvanized on DCSP. This would be a strong weld of 60,000psi but with more distortion. Weld splatter will need to be cleaned with a cup wire brush on a side grinder. Be sure and use a full face shield, long sleaves and gloves as the wires will come off the wire cup and stick into your skin, sometimes very deep.

With welding any galvanized steel, use exhaust at the weld joint for removing fumes. Also cock your welding hood to one side so the fumes/smoke roll by your helment and not go inside the hood. It's been known that drinking milk 1/2hr before welding galvanized will keep you from getting sick from the fumes. If you feel like you got the flu after welding gavlanized steel, your breathing to many welding fumes. Fresh air for one day will cure the problem.

You can also solder the joints with 50/50 solder. This is what they probably referring to by saying use what plumbers use. Very weak unless alot of joint surface area is joined together and is used a seal rather than a structual joint. Cheap to set up and cost is the lowest of all processes. Want to know more about this process let me know as there's a few tricks to soldering.

T_Bone

Try using bronze rods with the torch or 6011 rods with stick welder, grinding the areas to be welded, clean, will help, and after you can touch up the areas with galvanize available in spray cans, not galvanized paint but the proper stuff

Although 6011 is the correct spec'd rod for galvanized, from experience I've found 6010 ran DCSP is far superior when welding glavanized steel.

You don't have to preclean the weld joint as far as removing the galvanize and splatter clean-up is alot less.

Try it sometime.

T_Bone

On carbon arc welding I didn't elaborate on what happens when the carbon touches the silicon/bronze filler rod. You want to stick the carbon on top of the filler rod slowly pull back the carbon rod until the right temperature for a weld puddel to form.
You can leave the carbon rod on top of the filler rod thus heating the carbon rod tip cherry red and at that point the carbon rod will be very easy to break, more so than usual.

Mark Kw recently sent me a e-mail asking for suggestions on soldering glavanize SM(sheet metal) and I thought I would reply here to share with the rest of the board.
You have to have a sound SM joint, either by spot wleding or pop rivits or joint design, to start with or thin SM will seperate when the heat is applied. A 3/4" lap joint works well for strength as well as a seal but for round work a 1/4" to 3/8" lap will work ok.

The best heat source for soldering is a 1" copper soldering iron heated with a propane pot head. The soldering iron needs to have flat sufaces on four sides and called the "face", shaped by filing, then needs to be tined before using. Tining is accomplished by heating the iron to a medium heat then dipping the tip into cut acid, then applying 50/50 solder to the tip, then wipe off the excess solder on a cotton rag. Old blue jeans work well.

Cut acid is 40% sulferic acid(also called murratic acid, battery acid or pool acid) with galvanized SM chips put into a glass/procelin dish. Add enough SM chips to where the acid doesn't smoke(off gas) to much or much less than when first put in. Too many chips or if it's sits for several days it will kill the acid and a new batch needs to be made. If your having problems with the solder sticking or spreading evenly then suspect a cold iron or dead cut acid.

Next reheat the iron until the tined tip becomes bright silver colored. To much heat then the tip will burn and will have to be retined also seen as copper colored swrils on the soldering tip.

Next apply cut acid to the joint to be soldered with a acid brush only putting the acid where you want the solder to stick. Now you know what these handy brushes were designed for :)

Next apply the heated iron to the joint making the thickest part of the iron facing away from the lapp joint edge with the tip of the iron over lapping the SM joint by 3/8", then apply 50/50 solder to the joint sucking the solder back into the joint. Start by adding a small amount of solder and then you can see the solder suck( disappear) into the joint, then before you move the iron add solder to fill the lapp joint as you move. When the solder quits flowing into the joint then it's time to reheat your iron.

As your soldering you will notice a build up of black oxides on the soldering iron tip and face. This can removed by heating the iron, then dragging the iron thru a salamonic block rubbing it back and fourth alot. No you can't use this block to tin the iron although alot try.

If having solder flow problems, heat the joint with the iron then apply cut acid to the joint, then apply the solder to the joint.

T_Bone

Well there I go using the SM slang again. LOL
The correct name is soldering pot.

They make a propane head for heating the irons up. It connects right on the 5gal LP tank valve and has a small castiron encloser for the irons to fit in. Look for them at used equipment dealers as there hard to sell unless your in the SM business. You could make your own too. The object is not to have the irons in a direct gas flame. A piece of 4" channel iron bent at 150 degrees with 1/4" sideplates, over a normal burner head comes to mind.

Just cut up small scraps of galvanzied SM about 1/2" or so for cutting the acid. Doesn't matter what size container nor chips but a small glass bowl works well. Reread the part about "off gas" to see what I said on how many to add. It's a SWAG.

Glad I could help!

T_Bone

Second, I took note you said not to heat the iron directly in the flame. I have a copper iron that attaches to an LP torch head so that the flame only hits the back of the iron. Have you ever used these and if so, what do you think of them? I use mine on a Burns-o-matic trigger operated torch attached to a 20# tank with a 30' hose. Have only used it once doing some copper gutter work and it seemed to function fine. Will this also work for the galv or does the iron require indirect heating because of the acid used?

Your soldering iron will work great as I've used small ones in the past but I haven't seen a large face iron. It's been many years since I've done any CU gutter work and then we used the old style irons so thats a big improvement method.

The indirect heating is so the iron tining doesn't get burned off. You can use a direct flame to also solder with but it's very hard to control SM warp as it's very easy to over heat the SM and solder suck back is also very difficult to control on larger width seams. Solder suck back is for sealing the joint. This is where an iron will work best as there's more control over the heat zone and it solders much faster than trying to use a direct flame.

T_Bone