Underseal, Prepping For Underseal And Such Things

[BT]

Good Evening Retro Rides.

I am in need of some help and some advice. Over the years I have bought many a vehicle with the intention of building an awesome project out of it, never happened. I have however now been offered something which has had most of the hard work done. With my project failings I have never undersealed a vehicle.

What is the best approach?

The vehicle in question appears to have a very clean underside. There are a few areas of concern but everything is structurally solid. What is the plan of approach here? Am I going to want to take everything back to bare metal? This isn't my ideal method as I have quite a limited time scale to get the underside sealed.

There is a shot blaster round the way, but once I have sorted out transport to get it round there, waited, paid up, I cant help but think I would be better off going at it myself.

I am thinking, lay a mattress on the floor and roll the shell up and over onto its side so the whole underside is exposed. There are areas like the boot floor that are new panels. I was just going to go over this with a scotch pad to give us something to bond to. The areas that are of concern, and when I say of concern they have very slight surface rust, nothing structural or integral, would I just be able to go over these with either a fap wheel or wire wheel?

In respect to time scale, if focusing with the intention of completing a thorough and effective job as promptly as possible would it be possible to this in an evening? possibly 3/4 hours?

What is the stuff to buy?

I have access to a compressor, don't care if I have to use a brush or a roller. What is the stuff that I should be using? It will be on a mini, so not a huge area. Floor and up the inner wings. Ideally I would like something that I can paint over the top.

[3point141]

Hi, This is only my own opinion, if its really only patches, i'd pass on the sandblasting route. An afternoon knocking anything rust-coloured away with a wire brush in a drill or grinder, followed by rust-conversion (chemically, I recommend looking at the Bilt Hamber range, they're excellent) will get you where you need to be.

Then again, sand-blasting is such fun! you'd be missing out on a life-affirming experience, perhaps you should!!

After that, there's loads of routes you can follow for coatings. Let the discussions commence!

[BT]

Aug 14, 2015 19:00:27 GMT 3point141 said:

Then again, sand-blasting is such fun! you'd be missing out on a life-affirming experience, perhaps you should!!

Haha, I've done it. made me chronically sick. Never again!

Shotblasting is out the window because of the time constraints.

[colnerov]

Hi, I would think you may have to amend your timescale. you can't really underseal straight onto bare metal you need to prime it at the very least with red oxide, preferably paint as well. Don't use smoothrite or hammerite, they are for the garden not cars. Use a flap wheel not a wire wheel as they tend to polish the rust.

Colin

[3point141]

Just my 2p.. if you're chemically converting rust, use a wire wheel. Flap discs are abrasive & in even experienced hands, tend to remove good material as well as rust.

Etch-primer onto anything left as your first coat if you're following up with a normal paint system.

Or use a 2-part marine paint system: Epoxy 2-part primer & finish paints are a plenty. Some contain metal "cathodic" inhibitors, so perform well. To be honest, what approach you use depends on the paint system you decide to buy. I use "JOTUN", it's cheap & good enough for ice-breakers in the arctic...
Google a product to find the best means of prep, use etc..

Afterwards, under-seal using whichever under-seal system you decide to buy, there are loads to choose from. I always finish with wax-oil. Can't get too much wax-oil under a car. Just don't do it in winter, it does its best job by capillary action, & will not "wick" into the seams.

In the end, the best result will come from doing really in-depth research on your chosen product & doing the best prep work you can possibly do.

[taurus]

I've tried all sorts of methods, including some fancy and expensive stuff which didn't last very long at all.

The advice to avoid Hammerite is good - it's useless on cars. It's useless on trailers. It's useless on railings. It's useless on garden furniture. It's pretty useless full stop. I have no idea how they continue to get away selling the stuff.

What I use these days - primer - BondaPrimer. It's a high zinc content and easy to paint or spray. Only snag is that it's cellulose based and will react if you overdo subsequent coats so it's a case of thin and frequent rather than thick coats.

For paint I use Ronseal NoRust. Seriously, I first used it by accident on a boat trailer which I used to have to paint annually - it's not been done for 9 years since I did it with NoRust. In sunlight it will eventually crack, but under a car it's tough enough without going too brittle.

Underseal - I wouldn't use underseal as such. It's too thick and if you get any damage moisture gets trapped beneath it and you get hidden corrosion forming. I prefer to use a 50/50 mix of Waxoyl and cheap fresh 20/50 engine oil. Apply warm. Waxoyl (as said above) doesn't wick very well on its own. Mixed with engine oil it does.

The key thing is that this isn't a fit and forget job. Check annually and then touch up with Waxoyl / engine oil mix where and when necessary and it's keep the rot at bay.

[optimusprime]

I used to use Hammerite years ago, and i mean yrs,probably over 20 yrs ago, and it was always pretty good.

However i think they have changed the formula since those days, as over the last decade at least, when i've used it, i've noticed that it does not apply like it did,it needed a good couple of coats,and it never seemed to dry as hard ad it used to,and would soon wear off and allow rust to spread.


Will have to give that Ronseal a go,as i have a Land Rover chassis to paint.

[mikeymk]

I've got a few cans of tacky chain grease - goes on like WD40 but the atmosphere does something to it and it goes like ten times thicker than gear oil. You spray it on chains and it cakes up. Should be good for inside doors, quarter panels, anything that isn't subject to getting blasted by the rain.
Rear arches and sills tend to corrode from the inside out by condensation, so are not the usual areas for a tough-barrier stonechip type coating.

I've also heard of using anti-climb paint for these areas.

With these areas inside the bodyshell, i wouldn't use anything smelly. I like the smell of GT85 so much i'd wear it as an aftershave, but despite containing PTFE i can't see that being very protective..