Welding Tank by Galvanized Sheets

Do not weld anything that is already galvanised. The zinc-rich fumes are hazardous to the welding operative!

Taking into account what PWS has said about the hazards, there are many zinc rich paints that can be used to overcoat the welds.

You could use E316 filler metal, but why would you want to?

I assume that there are no specification requirements to be met?

WE have done welding on galvinized metal,

How we handling this was.

Wear PPE, resparators, googles, .....

Grind off galvinized material.

Ventlate area.

Than there is galvinized paints we use, you can just google it. I'm sure rustoleum has something.

If you want to use SS filler, talk to to your welding supply shop. 309 is the common choice for joining dissimilar base materials & would be my suggestion instead of 316, unless you anticipate serious chloride problems. Regardless, you will still have exposure on the base metal beside the joint so should consider the Galv paints as previously mentioned.

Phoenix911 is correct, but is this tank for potable water? If yes, the tank should be made of stainless steel, not galvanized steel.

Not like I haven't done it in the past, as we had gal tanks when I was a kid living in the 'outback', but I wouldnt want to drink from a gal tank if I could help it.

See your local welding shop about electrodes maybe. 316 L will work, buts its still going to rust where you have burnt off the gal at the edge of the heat affected area, so not really worth it.

We use this stuff called 'gal-stick' to re-instate the gal coating after grinding and welding. You just heat up the area with an oxy, rub it on quick-sticks, then clean it up with a wire brush...works a treat. Get it from any welding shop, pretty sure.

That or cold-gal zinc paint, but it probably wont be as good as gal-stick if semi/submerged in water.

As stated, there are products available to apply to welded joints. Here in the US, there is a product called "Galv-Alloy" which comes in square or rectangular "stick" forms, generally 12 to 36 inches in length, which is applied (melted) over the weld surface in a manner similar to a solder joint. This is almost certainly a product very rich in zinc, and appropriate personal safety should be adhered to. We have used in for years in making gate frames from galvanized pipe, and I believe holds up better to corrosion than a painted weld joint. It also blends in very well with the surrounding surfaces.

solution 1. you weld it taking welding pecaution, make holes where required, apply zinc primer, paint it and line the tank internally with fibreglass lining.

solution 2. If it is potable water use plastic tank white for indoor use and black for outdoor use. you may use prefab insulated sheet also contact sintex tank manufacturer

http://www.sintex-plastics.com/build&con/build_constru_usp.htm#SMC Panel Tanks

see smc panel tanks.

1.- Please explain 9x3x3

2.- Weld After and galvanized before welding.

Thanks all

Actually this tank for portable water, and I am sure the best material is GRP or SS, but the client specs is CS, and I can't change at this stage due to cost difference, but Iam trying to present good quality, because I had bad experience with normal epoxy painting, so for that I am trying to find other way,

Clarifying tanks are early in the system, where most suspended solids are removed by some air or flocculation process and is fitted with equipment to remove floating solids. The clean water is then fed to another container prior to injection of chlorine and any other chemicals to condition the water for human consumption.

A galvanised tank would be expected to last around 10years, if indoors and without further coating.

At last a spec.

If the customer wants CS then why bother with galvanised material? It seems that long service life is less important than low cost.

Give the client exactly what they asked for. What are the full specs?

How thick is the material?

Further to other replies, I would be wary of using galvanised tanks for potable water. By all means weld the seams to give a watertight joint but after that I would use a sprayed polyurea coating to fully seal the inside of the tank forever.

A British consultancy, Eco-Prokol have a CE Certified product, Rocathaan 136T, that is approved for use in the UK Water industry in contact with potable water. (BS 6920). Probably the only one (Pure Polyurea) in the world with that level of approval, and they give a 30 year guarantee as well. Basically you could spray it and forget it. It sets in 8 seconds so the tank could be in action immediately - no curing period. I've specified it for a number of UK Water Authority schemes and they love it. In fact, if the metal rusted the membrane would still remain in place holding the water on it's own.

I'm not keen on polymer hybrids or polyurethanes in water applications as they nearly all suffer from hydrolysis after a few years and many of them use DBTL (Di-butyl Tin DiLaurate) as a catalyst which is one of a number of organotin compounds that have potentially harmful side effects in humans and animals. Small risk but there all the same.

If you wanted to really save money you could just rivet it and line it with a single sheet butyl or EPDM liner that should last at least ten years or more but you would need to check it periodically. It a choice between cost/life/ease of application/ speed.

Hope this helps.

Do not weld with Stainless Steel. You run the risk of failure by the solid metal embrittlement mechanism.

Weld with a rutile electrode, the rutile will help prevent cracking.

Repair the galvanizing with a zinc repair alloy.

Alloy Trade name and manufacturers:

Galva-Guard - Teckcominco

Johnson #911 - Johnson Manufacturing Co.

Zaclon Galvanizing Repair Alloy - Gardiner Metals

Procedure:

1. Surfaces to be coated must be free of grease and scale. Degrease and clean with grinder.
2. Warm surface with torch.
3. Apply flux by rubbing on warm surface.
4. Heat surface to about 250^oC (480^oF) or until repair alloy melts upon contact with heated surface.
5. "Tin" surface by rubbing the repair alloy stick over the entire repair area.
6. Apply heat to repair alloy stick and melt off enough Galva-Guard to cover repair area.
7. Spread repair alloy with an appropriate application tool which has been dipped in flux and mold to desired shape and thickness. (eg. wood, ceramic, glass).
8. While still warm, use a wet cloth or sponge to clean excess flux

SS weld rod is a waste of money for this job. You will have to re-coat the entire weld joint as the galvanizing will have burned off at the joint. Weld with mild steel rods after removing the galvanizing at the joint will be just fine. I have used a brush on cold galvanizing compound in the past but do not remember the brand name. It worked fine for live stock tanks but I do not know if it is rated to be "Food Grade".

Question:

Do you mean potable as in for drinking purpose or portable meaning water storage for job site?

Has this tank design been professionally engineered? A seam failure with a full tank could have serious consequences. Personally, I would make sure I'm safe from any future liability claims.

If you are using a gravity tank, not pressurized, get a used farm milk storage tank, or dairy processing tank, it will be stainless and have a stainless 2" valve installed to the bottom to draw off from.

No welding, closed to most foreign matter, can be sterilized, and good for potable water.