Painting Diesel Tanks

[cindersailor]

Having just removed the mild steel diesel tank from my recently purchased boat I find that there is considerable corrosion inside, particularly at the bottom where water has obviously lay for some considerable time. The rest of the tank seem in very good condition so I am reluctant to replace it. I could just give it a good clean and refit, but I would like to paint/coat the inside to prevent future problems as getting it out is no mean feat. My question is, how does epoxy resin put up with extended imersion in diesel? No doubt there are special paints available but since I have some West System on the shelf that would be simplest/cheapest if it will do the job.

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[Plum]

Epoxr resin would be suitable, but only if you can remove all the corrosion oxide from the bottom of the tank back to bare metal and thoroughly (very thoroughly) clean and de-grease the surface otherwise the epoxy will not stick and you will have wasted your time.

How thick is the remaining metal at the bottom of the tank?

I would strongly recommend, for your own long term peace of mind and reliability, to go for a replacement tank in stainless steel or plastic. What is a reliable engine at sea worth to you?? I used to have a mild steel tank in my previous boat but now have a translucent plastic Vetus one which gives no such problems and you can also see the fuel level through it.

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[vyv_cox]

I suggest you get a welder to chop out the corroded tank bottom and as much as practicable of the sides and weld in a stainless steel replacement. The two will weld together perfectly. There is a potential problem of weld corrosion but unless the tank is immersed in seawater this is most unlikely to occur.

While he is at it, insert a drain plug to enable draining off water.

Carbon steel diesel tanks are a menace and you will be very pleased that you have spent this relatively small sum on avoiding the many problems that either flakes of rust or sheets of disbonded paint will inevitably cause.

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[upstream]

I think you have to way up the time and effort to remove the tank in the first place ( it may be a pig of a job) and the botch job by welding in bits and pieces or cleaning and coating with a substance that will in time come off. For my money I would replace the tank with anything within your budget, but do not try a cheap repair job. This will cost you in the end. Water draining is important as is filling the tank to the brim when wintered ashore. Drain valves are easy to come by and if the base of the tank is inacessable then a remote tube can be fitted to enable easy access to the valve.

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[oldsaltoz]

G'day Cindersailer,

I would have to agree with the posters above, a bog standard steel tank is a problem that will, in time give you problems. Putting a coat of epoxy over the corroded area may hold for a while, but the expansion and contraction of the steel will cause a loss of bond.

How much resin do you have, consider making a fibreglass tank, they last for years, are very easy to build and repair.

I hope this helps.

Avagoodweekend, Old Salt Oz /forums/images/icons/cool.gif

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