Coating stainless tank to prevent leaks

[daveNZ]

I have a 200 L stainless tank, that has corrosion? from diesel residue/acid/ or ? creating a few small worm-like trails that are up to 1mm deep. Given the stainless is 1.2mm we need to either replace with a plastic tank or create a safety net under the tank.
To do something inside the tank would involve 2 new inspection hatches to see past the baffles, and the cost of that is a long way towards a new plastic tank. Similarly the cost of welding a plate over the bottom is apparently not cheap.
I'm thinking of a coat of epoxy/fibreglass/?? Covering the bottom and part way up the sides. A leak will hopefully show up slowly allowing time to delay removing the tank again.
Am I wasting my time or is there a near bulletproof way of coating the underside of a stainless tank?
Thanks
Ps we are never more than 2 or 3 days from home marina.

[hellosailor]

dave-
In the States we have products like POR-15 and RedKote fuel tank liner. These are (totally different) liquids which you pour into a cleaned tank. Then rotate the tank and allow it to coat and dry all over. Mainly, the will stop pinholes (nothing larger) and prevent corrosion. There are other similar products, check the general aviation and motorcycle industries.
But if you've got 1mm of corrosion in a 1.2mm thick sheet...Even if you could apply a heavy exterior frp epoxy coating, I'd think it might be time for replacement. Or cutting open the top and putting a bladder in the tank itself. Less work than all the coating.

[Lepke]

I've coated big tanks with epoxy tank liner paint. The tank has to be oil free. After washing, I sand blast. The coating needs to cover the whole sides. Diesel will eventually get under fiberglass that is open at the top if you just go part way. Also it has to be with cloth. Not just resin. The stainless also needs to be sanded.
Tanks in my current boat are 1942 steel and had some deep pits in the bottom plates. After cleaning the tank, I welded the deep pits. 1/8" or so in 1/4" plate. If you don't know how to weld, a smaller tank would be cheaper to add a plate on the bottom.
I only use plastic tanks for water. In a fire plastic fuel tanks disappear.

[daveNZ]

Thanks for those replies. I have used Por 15 inside the one third of the tank I can access, between two baffles, the 2 ends are not accessible, so I assume there is more 'corrosion' there as well. I did a test patch of Por 15 on the top as well, and it peeled off almost in one piece after less than one year. The patches inside were probably better prep'd and look as though they have adhered well.
So, go to the trouble/expense of two new hatches $400 so I can clean the two ends, then Red Kote $100 etc, weld a new bottom on $400, or replace with polyethylene $700.
I think in the end the polyethylene seems more sensible!