TheSamba.com :: View topic - How to approach under hood pitting and other rust

Mon Jul 19, 2021 6:39 am

I am wondering what the best method of approach would be on the under hood rust pitting and other surface rust. I am in the middle of sanding and stripping many layers of paint. Should I remove all the rust, treat it with a rust killer spray and then put body filler in the pitting? I dont have a welder so that makes things a little difficult.

It doesn't look to bad to me, but not sure what the best approach would be.

Mon Jul 19, 2021 1:38 pm

Brush multi coats of satin silver & gloss black www.masterseriesct.com on it.
It will look good & be protected.

Mon Jul 19, 2021 3:05 pm

Or blast and follow with epoxy primer, put on extra thick in the corners and use a little filler before you paint and it will disappear... and shouldn't come back during our lifetime.

Just another slightly more involved option. That's how I would do if I were repainting the whole hood or more.

Mon Jul 19, 2021 3:26 pm

evanfrucht wrote: Or blast and follow with epoxy primer, put on extra thick in the corners and use a little filler before you paint and it will disappear... and shouldn't come back during our lifetime.

Just another slightly more involved option. That's how I would do if I were repainting the whole hood or more.

That’s the best solution. If you don’t have a blaster you can use naval jelly to chemically remove the rust in the pits. You don’t want to leave that black oxidization that’s still rust and any exposure to moisture will activate it.

Tue Jul 20, 2021 4:29 am

Thanks guys, how many coats of epoxy primer do you put over metal and filler before you paint a base coat?

Tue Jul 20, 2021 4:30 am

Don't put filler in the pits. These are under the hood, nobody will ever see this. Media blasting is going to remove more than you think, looks like there is some flaky rust that will blow out. Key is to remove as much of the rust as you can. If you can't get down to clean metal, neutralize whatever rust is left, and then coat over it so moisture can't get in there and restart the rust process.

Wed Jul 21, 2021 10:08 am

After getting rid of the rust. Epoxy - seam sealer - Paint.

Wed Jul 21, 2021 12:47 pm

i have a similar issue on my hood at the nose. what about lead? if i put too much on there, can i still file or sand it smooth like filler?

thanks

Thu Jul 22, 2021 4:53 am

I have watched videos of people using lead on old custom cars, I think Chuck Barris was in some? Some old guy with a cigar was doing it. I suppose you could file it or sand it, but remember it is lead, which is not good for you. Wear a respirator and contain any filings or particles that get ground off.

Thu Jul 22, 2021 9:22 am

Yes they file and sand lead. You put it on with this hot spatula thing and smooth it out while it's hot and finish it after it cools. The filing is minimal but neccessary. I'm not sure the nose of the hood is the best place for lead.

It behaves basically like solder, if you can imagine. Temp is key

Thu Jul 29, 2021 2:52 pm

How do I get the rust out of these raised areas? Under them, inside the holes there is rust.

Thu Jul 29, 2021 3:42 pm

Ive never tried the above, but for some ideas...

Use a flexible wire brush inside the holes. Blow the particles out with compressed air. Soak with ospho. Then primer of your choice.

And as an optional step, fill it with liquid rubber or something that isn't hydroscopic.

Fri Jul 30, 2021 6:55 am

Ok I am currently soaking under the raised areas with a paper towel soaked in evaporust. Im hoping it does a decen't job killing the rust. Its really hard to get in those areas to sand. I wonder if this is a common rust area? Im fairly certain its just surface rust. Im just worried after all this prep and time spent sanding the car down to bare metal that some unreachable areas are gonna ruin the paint job.

Fri Jul 30, 2021 7:49 am

kylewadescott wrote: Ok I am currently soaking under the raised areas with a paper towel soaked in evaporust. Im hoping it does a decen't job killing the rust. Its really hard to get in those areas to sand. I wonder if this is a common rust area? Im fairly certain its just surface rust. Im just worried after all this prep and time spent sanding the car down to bare metal that some unreachable areas are gonna ruin the paint job.

1) Drill out the spot welds and remove the bracing, clean out the rust, weld it back in.
2jBuy Navy jelly and soak the hell out of it repeatedly until it’s all gone.
3) Pour a rust encapsulator product like POR15 in there and then top coat.
4) find a non rusty hood.

Fri Jul 30, 2021 9:54 am

Braukuche wrote:

1) Drill out the spot welds and remove the bracing, clean out the rust, weld it back in.
2) Buy Navy jelly and soak the hell out of it repeatedly until it’s all gone.
3) Pour a rust encapsulator product like POR15 in there and then top coat.
4) find a non rusty hood.

Are those steps in order, or 4 different options. Sorry super noob here.

Fri Jul 30, 2021 10:35 am

kylewadescott wrote: Braukuche wrote:

1) Drill out the spot welds and remove the bracing, clean out the rust, weld it back in.
2) Buy Navy jelly and soak the hell out of it repeatedly until it’s all gone.
3) Pour a rust encapsulator product like POR15 in there and then top coat.
4) find a non rusty hood.

Are those steps in order, or 4 different options. Sorry super noob here.

Sorry, different options.

Fri Jul 30, 2021 5:13 pm

This may or may not work re sealing. I've done it on other non-accessible parts but am not sure about YOUR specific hood.

Get some plasticine or linseed oil based window putty or maybe Play-Doh. Seal all the outer edges of the double sections. Or do what you need to if you hold the hood at an angle to the horizontal.

Fill with Ospho or rust converter. Let it do its magic. Slosh around to make sure it gets into all locations.

Drain out any excess liquid from one or two spots by removing sealer and leave to dry. (Or if a proprietary rust converter follow the instructions - some say dry some say leave wet or needs to be washed. If using water then use hair dryer/hot air gun to dry water off).

Reseal the edges previously removed.

Flood area with your choice of anti-rust paint. Slosh around to make sure it gets into all locations. Leave to dry.

Remove the sealing and clean area with acetone/lacquer thinner etc to make sure all oiliness from the plasticine/putty/Play-Doh is gone.

Even if you cannot get a perfect seal, the idea is to get the rust converter and paint into areas that you cannot reach. If a little leaks here or there it is no big deal. If you intend to keep the original paint though, make sure you wipe it off the paint surface immediately and not let it dry.

Tue Aug 31, 2021 12:48 pm

Try acid dipping.

Tue Aug 31, 2021 3:50 pm

Michael Ambrozik wrote: Try acid dipping.

That's essentially what I suggested using the "dam" method.

Acid dipping is the better way, but you need to find a receptacle big enough to hold the part. Small parts are easy, the hood is a different matter.

One way is to get a kiddies pool of the right size and use water with some pool acid (Hydrochloric acid) in it. The problem here is the volume of water and acid you need plus the danger of someone getting onto the pool.

The other more long-winded method is to build a narrow rectangular wooden box the depth and width of the hood up to the area to be treated, place a plastic bag or tarpaulin in it and then fill it with water and acid, the same way.

My acid of choice is Citric Acid which is a food acid, relatively benign (i can have my hands in it with out gloves) and does a great job in removing rust. You can put it in a drum when finished and just keep using it up. You can usually get it at bottling places or perhaps home brew supplies. Citric acid is a powder. Make up a 10% solution by weight of acid and water. 9kg or 9 litres of water and 1 kg of powder. Soak for a few days, then thoroughly wash with water and then bicarbonate if you choose. It has the added benefit that it loosens if not remove completely the old paint that VW used. This can be a good or bad thing. Read below.

Whatever method you use for rust converting, you need to paint it pretty much immediately lest the bare, clean and very reactive metal starts to rust again. The same problem occurs. How to get paint into the hidden cavities? Hence the use of the dam method.

The other issue with acid dipping is that depending on how long you leave the item in the acid you WILL get a mark at the air/liquid interface. That is, the area that is submerged in the acid will be etched a bit like sandblasting when it has removed the rust, whilst the bit in the air is unaffected. This will usually just sand out, but the longer you leave it, the worse it can get.

Finally, acid only eats rust, not good clean steel.

Sun Sep 05, 2021 4:15 am

Do what viiking suggests. Full strength Ospho is your friend. If nothing else use wire whe or brush or scrapers to remove crusties and then a wet paintbrush or spray bottle or anything you can use to get it soaked.After you know it's all wet with ospho, wipe up around and put a fan on it to dry. You can paint directly over it , but probably best to clean up some and remove white residue if heavy. I'm working where the humidity is over 80% most days and have left unpainted but Ospo treated metal for weeks.. No Rust. Don't mess with all the other treatments which are just phosphoric acid mixed with other unused stuff, straight Ospho is best.