> One thing I didn't like about this FAQ (sic) was the suggestion to use
> Muriatic acid. This is pretty strong stuff - even the fumes will rust
> nearby unprotected metal - had this problem when I was using an open vat of
> this acid to de-rust steel parts. I buy phosphoric acid in solution sold
> as milkstone remover at the farm supply store. It works very well, and, I
> might be wrong, but I've always been told that phosphoric acid leaves a
> coating on the metal that helps resist further rusting. One fellow once
> suggested (on this list, I believe) that I use phosphoric acid diluted with
> water as a panel prep. Wipe the panels with an acid-soaked cloth and then
> dry them well with a towel and compressed air. No rinse. It seemed to
> work, but I did this where I wasn't spending a big chunk of change on the
> top-coat paints.
I don't recall my acid games well enough to comment precisely, but what you say
rings a bell
or two in my head. Both on the strength of Muriatic acid and the use of
phosphoric acid as a
panel prep. In fact, I'm almost positive of the latter.
> So why does everyone recommend using the tank coats? I'll try one of my
> bike tanks without it and see whether that works.
I don't know. Guess for the same reason people buy gas line magnets and Slick
50. Actually,
I don't think the concept of coating the inside of a tank with something is
completely
wacked. But coating it with something inflexible, brittle and hyper sensitive
to surface
prep is a bad idea imo. You need something that can handle the flexing a large
panel is
going to see, and that can reasonably be applied. All the tank sealers I've
seen fail on
both accounts. Someone here just posted a comment about some other tank
coating material
that seemed more reasonable I think. But I of course cannot remember any of it
now. I did
come across something in my ancient Dykes Auto Encyclopedia I'd like to check
out.
Apparently old cork carburetor floats were covered with shelac to seal them.
If shelac is
truly impervious to gas, that might be a very good tank coating agent. It's
got some
flexibility, could be applied reasonably well to the inside of a tank, and
isn't hyper
sensitive to surface conditions prior to application.
> The Buick club magazine had a write-up on tank restoration. Their
> suggestion for car tanks was to cut holes in the top of the tank and use a
> combination of acid and grinding wheels to remove all traces of rust. Then
> weld metal back in to cover the holes. Not a bad idea for irreplaceable
> tanks. I've thought of doing this on a bike tank, even - especially to
> gain access for removing dents. Of course, you need to remove all traces
> of gas and fumes from the tank before cutting and welding.
Fill the tank to the tippy top with water, drill and cut to your hearts
content. You can
even weld that way if you get the portion you're welding right up at the top so
water doesn't
dribble into the weld.
I don't know about car gas tanks, but most motorcycle gas tanks are joined with
solder seams.
While I've never done it, it seems to me you should be able to take a tank
apart by melting
the solder out of the seams. And then of course put it back together by
soldering it back
up. Something I'd have to farm out. Never was good at soldering or brazing.
Always
overheat things and try to weld them instead.
As for the fumes, a gallon of acetone sloshed around in the tank with
enthusiasm will cut the
gas clinging to the walls. Drain it and blow it out well, and if it were my
tank, I'd still
let it sit outside for several days. In fact, I'd try to rig up a blower to
blow air
through it while it sat there. You then should be able to weld on it without
danger of
explosion. I'll emphasise the should here, that's should, not a guaranteed
will. If it still
stinks of gasoline, I wouldn't put heat to it yet.
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