Protecting a fuel tank cradle from the elements - what coating is optimal?

[Ubique]

We've been asked to replace a fuel tank cradle as the old one has significant rot - it's mild steel and as usual, the rot starts from the fuel tank side where it will never really dry out, or at least not quickly. the underside will also be subject to stonechips etc. The owner wants this one to 'last a bit longer'....
My thinking so far:-
Powder coat - OK for the tank side, poor for resistance to stone chips.

Car body cavity wax over paint on the tank side, Dinitrol 4941 over paint on the underside, OK to good for the underside, OK to poor on the tank side as the wax will eventually dissipate under the pressure of the weight of the fuel tank.

Line the cradle with 'Gardeners Fleece', spill mats or something along those lines, then spray on the cavity wax, the material will (hopefully) prevent friction. Dinitrol 4941 on the underside. The only downside I can see is if the material does not fully absorb the cavity wax and leaves pockets where it can hold water.

Just get it heavily galvanised and be done with it!

This is a similar cradle, as you can see it's a saddle tank.

Any of those ideas jump out as good or really bad? - or does someone with experience have a solution?
Thanks.

 

[addjunkie]

Id probably get it galvanised, but your Dinitrol both sides would probably make it outlast the motor

 

[dave h 2]

Fleece, I wouldn't put anything that holds water even indirectly inside a shield like that.
My go-to would have been stone chip, ,but that's the 1990's talking.

 

[Ubique]

Ohhh - you just reminded me, there was some tins of 'underseal' that had fibres in, very dense (and probably a H&S nightmare now!) and it dried with a thick 'skin', that'd probably be ideal for the tank side - or both.

Edit: This looks like it'd be OK for the tank side https://www.carbuilder.com/products/wunderseal-underbody-sealer

 

[reb78]

I think on my 110, I painted the cradle and then smothered it in waxoyl on the tank side at the time, then stuffed it all back up whilst the waxoyl was wet. That was getting on for 20.years ago now and its not showing any sign of rusting through.

 

[willie.macleod]

Raptor both sides, works well in our salt spray environment here. Galv good but is the customer willing to wait for it to go in with a batch, it'll still need a coat of something on top as well for the long term.

 

[Ubique]

Never heard of Raptor - is this the right stuff? https://raptorcoatings.com/product/raptor-1-gallon-roll-on-kit/

The tank cradle is on backorder but 37 are supposed to be in the distribution centre next week, they're happy to wait.... maybe galv & Raptor?

 

[sako243]

Once you've got galv on it then anything else in my opinion is a sacrificial coating to further protect the galv.

Something rubbery and softer would be my go to for stone chips.

Raptor both sides, works well in our salt spray environment here. Galv good but is the customer willing to wait for it to go in with a batch, it'll still need a coat of something on top as well for the long term.

Depends on if you can find someone to tag in on their load. For example CLH Trailers down our way sent a lorry every week to galv, think it's collected Tuesday morning and back on Thursday. They're quite happy for people to chuck smaller bits onto the lorry to get galved alongside their trailers.

 

[Craig-SM]

I was going to suggest Raptor paint too. I’ve used it on the Shogun first on the steel bash plates and towbar frame. They’ve held up well. Then about 2 years ago I replaced the fuel tank and fuel pipe. Both of them got the Raptor treatment, they both appear to be doing well

 

[willie.macleod]

Never heard of Raptor - is this the right stuff? https://raptorcoatings.com/product/raptor-1-gallon-roll-on-kit/

The tank cradle is on backorder but 37 are supposed to be in the distribution centre next week, they're happy to wait.... maybe galv & Raptor?

That's the stuff, it'll roller on or spray with schutz gun (note it contains isocyanates). Galv and raptor would ensure you didn't have to do the job again for sure. You can get raptor in aerosol tins as well but no experience of those.

 

[Ubique]

Great, thanks!
There's a hot dip galv place about six miles from work so I'll suggest it goes there first then 'someone' can spray it with a mask on!

 

[Kram]

We've been asked to replace a fuel tank cradle as the old one has significant rot - it's mild steel and as usual, the rot starts from the fuel tank side where it will never really dry out, or at least not quickly. the underside will also be subject to stonechips etc. The owner wants this one to 'last a bit longer'....
My thinking so far:-
Powder coat - OK for the tank side, poor for resistance to stone chips.

Car body cavity wax over paint on the tank side, Dinitrol 4941 over paint on the underside, OK to good for the underside, OK to poor on the tank side as the wax will eventually dissipate under the pressure of the weight of the fuel tank.

Line the cradle with 'Gardeners Fleece', spill mats or something along those lines, then spray on the cavity wax, the material will (hopefully) prevent friction. Dinitrol 4941 on the underside. The only downside I can see is if the material does not fully absorb the cavity wax and leaves pockets where it can hold water.

Just get it heavily galvanised and be done with it!

This is a similar cradle, as you can see it's a saddle tank.

View attachment 534463

Any of those ideas jump out as good or really bad? - or does someone with experience have a solution?
Thanks.

Looks like it has several depressions that will hold water and could use drain holes added.

Does the exhaust run down the middle? In which case it is also acting as a heat shield? If so, whatever is used should not be too flammable.

 

[Ubique]

The depressions are there to prevent vibration / resonance, because of that, I'm wary of drilling holes - I'll have a discussion about it tomorrow but my immediate thought is to keep layering Raptor until they're full....
The propshaft runs at the top, then a heatshield, then the exhaust - that was one of my concerns about using body cavity wax, it may re-liquify if there is enough radiant heat from the exhaust

 

[dave h 2]

Ask about the effect on the tinplate from the molten zinc it may cause warping