leaking stainless steel water tank

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davidivorwynphillips

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I've got a leaking stainless steel tank with multiple pin hole defects in the welds - the usual problem. I've decided to get it rewelded and have found a skilled TIG welder to do it. My question is can this sort of corrosion be prevented? For example completely emptying and drying the tank during the winter months - hard but not impossible. Or is it something that has to be accepted.
 
davidivorwynphillips said:
I've got a leaking stainless steel tank with multiple pin hole defects in the welds - the usual problem. I've decided to get it rewelded and have found a skilled TIG welder to do it. My question is can this sort of corrosion be prevented? For example completely emptying and drying the tank during the winter months - hard but not impossible. Or is it something that has to be accepted.
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I had the same problem on my Oceanlord. Vyv Cox of this parish recommended that - rather than re weld the seams, that I just cover with a layer of epoxy over glass tape. Getting the tanks out was quite easy and once out the job was simple - if a little messy.

I did 2 coats - 1st with glass fibre tape plus thickened epoxy resin, and then next day a final coat of thickened epoxy. The glas tape was 2 inches wide approx.

You can do the job your self so cheaper. I hate to think of the problem rewelding already crap welding!
 
Vyv, referred to by Chris Robb, is your man on this. But yes, pinhole development is a known issue with stainless steel tanks, although some will last for decades without problem. According to Calder, pinholes propogate more readily in areas where moisture can accumulate, such as at any dips and at contact points over bearers -- and especially in the absence of free airflow. Because welding alters the nature of the steel, seams are particularly susceptible, as in your case.

If I'm inferring correctly, David, you're luckier than some: at least you can get the tank out without major surgery. Good luck.
 
A German marine engineer I know does something different; he uses a thick wrap type material glued to the inside of the tank. The seams are heat sealed and guaranteed. However, he is in Majorca.
 
Had the same problem with a water tank. Had plates re-welded over the defective seams. Known problem with stainless welds and good reason for using plastic, but if the tank is easy to get out worth trying a repair. Mine cost only a few pounds compared with £800 for a new plastic one and I made sure it was easy to get out if it failed again. not sure emptying would make any difference as the inside will still be damp.
 
macd said:
Vyv, referred to by Chris Robb, is your man on this. But yes, pinhole development is a known issue with stainless steel tanks, although some will last for decades without problem. According to Calder, pinholes propogate more readily in areas where moisture can accumulate, such as at any dips and at contact points over bearers -- and especially in the absence of free airflow. Because welding alters the nature of the steel, seams are particularly susceptible, as in your case.

If I'm inferring correctly, David, you're luckier than some: at least you can get the tank out without major surgery. Good luck.
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Sort of - I'm still nursing a hole in my finger!
 
I have often wondered of cleaning a stainless steel weld with pin holes with acetone then painting the weld with penetrating epoxy like sealing the end grain of plywood would seal the welded stainless steel joint.

Any one any comments.
 
Rogershaw said:
I have often wondered of cleaning a stainless steel weld with pin holes with acetone then painting the weld with penetrating epoxy like sealing the end grain of plywood would seal the welded stainless steel joint.

Any one any comments.
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I repaired a leak in the weld of a stainless steel holding tank with Araldite, applied from the inside. It was an easy to reach leak, just inside a welded outlet pipe. The repair lasted many years.
 
pvb said:
I repaired a leak in the weld of a stainless steel holding tank with Araldite, applied from the inside. It was an easy to reach leak, just inside a welded outlet pipe. The repair lasted many years.
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Yes I have done similar repairs using our equivalent to Araldite but it does need correct preperation to get a long lasting job. I repaired a pitted o-ring groove using Pratley putty (our Araldite) and my diesel generator and it has lasted some time.

I was thinking that where anyone has pin holes the penerating epoxy would flow into the pin holes and thus seal then better than a covering or surface stuck epoxy putty.
 
davidivorwynphillips said:
Yes I did a temporary repair with epoxy last summer but despite abrading the steel before application a lot has become detached.
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Sorry to hear that. I have not had any problem as all with the bonding of the epoxy. I can understand why you want to weld - but I still wonder at the cause of the epoxy becoming detached - which would have been a much simpler job.
 
The OP doesn't say what the tank is being used for. If it's water then you can get a large neoprene/rubberised bag made up to fit inside it. As the bag expands with water it assumes the shape of the tank. When water in bag is used the bag reduces and thus self-baffles the remaining water. There was a company on the Isle of Wight that formerly made hovercraft skirting which will do a made to measure job. Might be named Seaflex but not sure if this is the correct company.
 
Oops, just noticed the heading clearly states it's a leaking water tank. I secured my water tank bag inside the perforated stainless steel tank with ties to a series of clips which I riveted into place. Bag holds 300 gallons and has now done 16 years with no leaks.
 
Sinbad1951 said:
Bag holds 300 gallons and has now done 16 years with no leaks.
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Would you care to reconsider that? That's over 1.3 tons.

Sinbad1951 said:
There was a company on the Isle of Wight that formerly made hovercraft skirting which will do a made to measure job. Might be named Seaflex but not sure if this is the correct company. .
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You're probably thinking of HCL and their 'Duratank' range, which are, indeed, excellent: http://www.hovercraftconsultants.co.uk
 
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Sinbad1951 said:
The OP doesn't say what the tank is being used for. If it's water then you can get a large neoprene/rubberised bag made up to fit inside it. As the bag expands with water it assumes the shape of the tank. When water in bag is used the bag reduces and thus self-baffles the remaining water. There was a company on the Isle of Wight that formerly made hovercraft skirting which will do a made to measure job. Might be named Seaflex but not sure if this is the correct company.
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Yes but what do you do about the baffles in the tank which seem to be solidly welded to the sides?
 
I crawled into my tank and cut out the baffles with a grinder/cutter.

MacD: Why would I need to reconsider the tankage of my vessel.
 
While it is possible to use them inside an existing tank, most tanks of typical yacht size will have baffles like yours so it is not practical. They are normally used as alternatives to a solid tank in a locker.
 
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