Diesel melting Galvanized pipe

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Has anyone ever heard of Diesel melting the gal coating off the inside of Galvanized pipe and galvanized fittings.Here in OZ we now have to fit bottom fill kits to all overhead on farm diesel fuel tanks, so the fuel delivery driver can fill the tank from the ground. All the kits I have seen are just Galvanized pipe and fittings.But I have heard that diesel may melt the gal and cause problems in the tractors fuel system. Has anyone heard or had any experience with this?.Simonhttp://members.optusnet.com.au/~abba/index.html
Reply:i have done a lot of work on diesel powered equipment and never herd that beforeChuckASME Pressure Vessel welder
Reply:I've never heard of it either. I've pumped diesel through galvanized pipe into my tractors for years with no problem. Galvanizing is nothing more than a zinc coating elctrostaticly applied like chrome. The diesel is nothing more than a light oil nothing corrosive about it. I guess it would be possible to have a bad batch of galvanized pipe. That 's all I can think of.
Reply:It has been a very long time since I've been on a farm, but if I remember right the tanks where all painted on the ouside.    Never much in the way of plumbing to be sure.   You never see gavanized hardware anywhere on a diesel.    Generaly either a steel or copper plumbing arraingement.     Much the same in the marine industry where copper is offen used for fuel lines.Now that is what I remember, so don't go to far on that.   Just geussing there could be issues with the diesel loosening the gavanized coating and having it flake off.    I do know that gavanized is not permitted on compressed air lines for similar reasons.    While I don't have the specific evidence, relating to this application, what I do know has me suggesting that you don't do it.    The issue is that that plating doesn't stick as well as some may think it does.Now for the big question - what is the rational for bottom filling the tanks?    That seems to be counter productive as it will tend to stir up all the sediments in the tank.   ThanksDave
Reply:When I was fabricating a diesel storage tank I read somewhere not to use galvanized pipe for the dip tube.  Apparently, something in diesel fuel reacts to the zinc and causes problems.  It was recommended to use black pipe.  This is my recollection from several years ago.  I'll research it and find the reasoning.RonL
Reply:Could be there are some issues with electrolysis. Steel tank/stand, maybe brass valves, galvy pipe, ground contact. Pretty common on a small scale. It's what dissimilar metals do.Take a small piece of galvy anything, a small pice of common steel and a brass/bronze chunk of something and put them in a little container all touching together outside. In a few months you'll see the galvy starting to turn white and cruddy. Must be filling from the ground so the "old" guys don't have to climb the ladder anny more, eh?
Reply:A search of "diesel and galvanized" shows several sources that state not to use galvanized with diesel.  They state that the zinc reacts with the diesel and is held in suspension until it is deposited on downstream parts ( filters, engine parts, etc.).  The quick search did not show me the exact chemical reaction, but I suspect that it is sulphur reacting out with moisture to form sulfuric acid. Sulfuric acid would react with the zinc.  I will search for something more definite when I have the time.RonL
Reply:Here's a little something to support what RonL is stating.http://www.eng-tips.com/viewthread.cfm?qid=48380Of course, read the whole thread but note Lilliputs post at the bottom.
Reply:Thanks everyone for your help, I had heard something about it and just wanted to see if it was correct.Wizzard the bottom fill kit still fills from the top but the driver stands on the ground and pumps the diesel into the tank via a pipe that runs up the side of the tank and into the top. Australian occupational health and safety now states that it is now mandatory for all overhead on farm tanks to be done for safety reasons.I will have to look into a different way of plumbing the tanks, Maybe black (steam) or brass fittings.Simonhttp://members.optusnet.com.au/~abba/index.html
Reply:You may find it's cheaper to do your piping in stainless than brass.  I think brass most pipe is DOM while stainless pipe can be purchased rolled and welded which keeps the price down.
Reply:GMC was correct I found stainless steel fittings to be the best option.All brass and copper products have just had a 45% to 55% price rise, That made stainless look even better.I have just assembled the first three bottom fill kits and will fit them to the tanks later this week.Simonhttp://members.optusnet.com.au/~abba/index.html
Reply:Sandy, the reason the galvanizing turns cloudy is that the very purpose of galvanizing is to be a "sacrificial" coating.  It is not that the zinc is a particularly corrosion resistant material (it's not) that protects the base metal - it's that when electrolytic corrosion does occur, the zinc goes first (sacrifices itself).  Such protection works well in the outdoors, in water heaters (until the cathode rod corrodes away, then the tank starts to corrode through pinloles in the glass lining), and on steel boat hulls where large blocks of zinc are put on the outside of the hull and electrically connected to the hull.  The "cathode blocke" are expected to corrode away and be periodically replaced.  It's not a good protection scheme inside a diesel tank (or a hydraulic oil tank) where the corrosion product of the zinc (zinc oxide, I suppose) has no place to go except into the engine or the filters. The position of zinc in the sequence of electrical potential (don't remember the exact terminology) is such that it preferentially corrodes when conditions are right for electrolysis to occur, protecting the steel in the process.  The product is the white crud you see.  The moisture that inevitably condenses inside a tank subject to daily temperature fluctuations and to temperatures below the dew point at night results in the accumulation of water in the tank and creates the conditions conducive to electrolytic corrosion.awrightLast edited by awright; 07-16-2006 at 09:56 PM.