Question about electrolysis

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Does anyone have input or have you seen/experienced electrolysis degradation of 316 stainless steel when used in the construction of a water tank when NO dissimilar metals are in contact with the stainless steel vessel?The chemistry of the water entering these vessels is as follows: 13,000 ppm of dissolved solids, hardness is 40 grains per gallon, iron level in water is .5 ppm. We are seeing leakage occurring along the welds of these tanks that have only been installed for 30 days.  Manufacturer claims electrolysis is occurring because of stray electrical current. Any suggestions or comments are welcome.  Thank you.
Reply:Originally Posted by LarryTheWaterGuy..... construction of a water tank when NO dissimilar metals are in contact with the stainless steel vessel?.....
Reply:There is no sacrificial anode. Plumbing connections are from a in ground copper pipe, to PVC tank adapters to the plastic control head that is screwed onto the stainless steel tank.
Reply:What type of pump is being used ?Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:no pump on this system, it is municipality supplied water.
Reply:Is this a buried tank ?Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:no, the tank sits above ground on a concrete slab.
Reply:Can you place rubber underneath it ... to isolate it from the concrete ( which can carry electricity ) ?Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:Originally Posted by LarryTheWaterGuyDoes anyone have input or have you seen/experienced electrolysis degradation of 316 stainless steel when used in the construction of a water tank when NO dissimilar metals are in contact with the stainless steel vessel?
Reply:Originally Posted by Mechtician...Most of my experience with SS water tanks is in the context of DI water cooling loops. Some questions for you (I understand if you can't answer due to confidentiality agreements):1) Is the tank pickled or passivated prior to installation?2) Which welding process does the manufacturer use to weld the tanks, and is the back of the weld purged or not?3) What is the shape of the tank, how much water does it hold and is it subject to any vibration?
Reply:I did find 0.015V DC between the side shell of the tank and the copper plumbing coming out of the ground.  I had not tested the water in the tank.
Reply:You said that there was no dissimilar metals in your first post, but in your most recent post you mentioned copper piping.    Copper and stainless steel are pretty close on the galvanic scale, but copper and stainless are dissimilar metals.You might consider using an electrical cathodic protection system, this would use a power supply to push the corrosion to the anode.   The downside of an electrical system is that it needs to be monitored, and a malfunction of the system can accelerate corrosion.     The traditional magnesium anodes are probably safer and cheaper, but need to be replaced from time to time.I agree that the only way to have corrosion leaks in 30 days is stray current.  You are going to have to chase the source of the stray current.   The suggestion of using a milivolt meter is a good one.   A high end voltmeter rated for measuring very low voltages might be preferred.  You would be able to find the source of the stray current by the simple method of turning off circuit breakers.   When the voltage drops abruptly, you have found the source of the stray current.  You would need to fix the stray current first, then apply cathodic protection.I have a little experience with corrosion in underground water pipes, spent $1M of the company's money replacing pipes that were less than 20 years old.One key issue, which you did not tell us, is the conductivity of the liquid.   The more conductive the liquid, the faster the corrosion will progress.RichardLast edited by raferguson; 05-04-2011 at 06:45 PM.Sculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge
Reply:Originally Posted by LarryTheWaterGuy1) Is the tank pickled or passivated prior to installation?I am not sure, I have never heard these terms used in corralation with water tanks. 2) Which welding process does the manufacturer use to weld the tanks, and is the back of the weld purged or not?We know the tanks are welded with an automatic MIG welder, but we do not know if the back of the weld is purged or not.3) What is the shape of the tank, how much water does it hold and is it subject to any vibration?It is a round 16" diameter by 65" tall and tanks contain 4.5 cu ft of pyrolox filter media for iron removal, and water volume is roughly 50 gallons of water in the tank.  They are not subject to any vibration.
Reply:Electrolytic/galvanic corrosion is just one of the possible maladies affecting stainless steel.  The other big one we see commonly in a marine environment is crevice corrosion caused by continuous exposure to a damp anoxic environment.  The lack of oxygen prevents the formation of chromium oxides, which in turn leaves the surface of the steel unprotected.Since you say the leaks are coming from the seams, I have to wonder whether pits are forming in the welds due to contamination or lack of passivation?  Once a pit forms, it is going to deepen pretty quickly in the environment you describe.
Reply:If you can post close up pics of the weld exterior and interior, that would help a bunch-asto degradation of the welds due to poor or no back purge/paste coverage.Blackbird
Reply:With stainless steel, you can get galvanic corrosion starting at a microscopic level between the metals in the alloy (iron, nickel, chrome, etc.), and once it goes from being "passive" to "active," the corrosion can accelerate pretty fast.316 is pretty corrosion-resistant, but it's not immune.Google "crevice corrosion" for more info.