Prepping Rusty Areas Underhood Before Paint

[andy72]

I posted a month ago about what paint to use under hood.  As I got into cleaning my project, there is more surface rust than I had hoped.

I was just going to shoot it with Rust-o-leam rattle cans.  Then I become pretty convinced on the Eastwood 2k underhood black system.

I am well aware of POR 15.  I coated almost my entire interior with POR after I welded in new floor pans. 

I am not excited about seeing brush strokes left behind by POR15 when I spray over it with the finish coats.

Do really have to get ALL the surface rust off before I paint?  (whine,whine) It's a pain in the Butt underhood.

Any other thoughts?  Rust removal jellys?  I've never used them.

Anybody approach an underhood cleanup like I'm facing and figure out something that made it easier.

I'm not looking for perfect show quality, but I do want it to look nice and last.

 

[midlife]

Rolloc pads and either an electric or air-powered drill work really well on removing surface rust.

https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Roloc-Green-Corps-Abrasive-Disc/?N=5002385+3293194015&rt=rud

 

[MikeGriese]

Get as much of the rust off that you can, and make sure the surface is as clean as possible before applying paint. You might consider a rust stabilizer to get into areas you can't reach mechanically. You can never get good results over poor preparation.

 

[Hemikiller]

Get some POR-15 Metal Ready, or any of the other rust removers such as Ospho, Evapo-rust etc. They'll take care of most -surface- rust in no time.

 

[OzCoupe72]

As Midlife mentioned the Rolloc pads work well

As an inexpensive de-oxidiser you could use ordinary vinegar about 50/50 with water to prep the bare metal, spray it on and leave it on for 10 minutes, heavier areas I'll use a scotch brite and work it in, rinse with water, dry thoroughly then epoxy primer

Trick is to get some epoxy (not etch) primer onto it ASAP once prepped

 

[kcmash]

Go ahead and do the following:

1) Remove the brake booster and clean it up.  

2) Remove the wire Harness for underhood

3) remove your fenders

Looks like you have some AWESOME metal to work with.  Use the metal pep mentioned above and spray a nice satin black coating on there.  You will be so happy!!

kcmash

 

[Pegleg]

I would go down the route of sandblasting with that much rust.

If you don't want to go down that route you can use por15 using a spray gun. If you check the por15 website it states the same as long as you dilute with thinners by no more than 20%. My engine was sprayed using por15 engine enamel diluted by 10% so i know its possible

 

[Fabrice]

I do feel your pain... I'm in middle of a big rust fight for a few months now. I did this on my 73 and and I'll be soon once more enjoying this job on my 71.

If of any help, here's my advise, based on own sweat and tears.

First, you should stop working for your eyes and should focus on a location at a time. I mean by that that it feels good to have the entire compartment sanded, but its of no help. Pick a location epron, cowl vent etc and stick to it till it shines. Light rust generates loads of dust, the very same dust will bloat your sanding paper and you end up spreading a powder of rust instead of the paint/rust bellow. Plus when you work on big areas, the "nobody_will_notice_if_I_skip_this" demon, will hit you!

By the look of the rust, I'd first buy a rotating brush, not the type with long wires, one with twisted wires. They look mighty and one may think its gonna rip off your entire metal. In practice they don't but do 10 times more efficient brushing that the regular long wire ones. Work from lower body to top. (gloves, mask and googles are must must, sound protection is no luxury for this kind of brush).

Once you have the metal free, there will be places where the brush can't go. Use then hand brush and sanding paper.

Rince with clear water. dry it or let it dry. if the surface isn't metal everywhere, fix the bits where there is deposits, often around bolts kept in place.

Using thinner or aceton. remove any trace of grease.

Then use something like evaporust, or the better one from eastwood. These not avail here in europe, so I use Rustico, which is a similar product and gives excellent results on this kind of rust.

These work best if they stay wet. Because you can't do that, prep a bucket with 3 liters of water with 50% or more of that stuff. Using a sponge or rag saturated of liquid, spread the product on the metal, you will see the deep rust turning black and the light one dissolve. Let it wet as long a you can. rince with clear water. For very thick rust, use the product pure with a paint brush. Depending on result, reapply or let completely dry. That stuff goes down to metal pores. When its dry, it leaves an ugly yellowish surface but that ugly layer is also excellent oxidation protection and offer excellent adhesion to primers. Its a ton better than rust transformers as rust is really gone, and you paint on a solid surface, not a transformed layer of rust with rust underneath.

Pick another location and repeat till compartment is done.

Then I'd spray first a thin layer rich in zinc primer or epoxy primer. Then your paint will look good and stay good for a long time.

Its a very dirty work for sure and you will need to sacrifice at least a weekend, but if you do not remove all that rust, no matter the paint quality, it will be a camouflage and you will have to redo this sooner than you think.

+1 on removing the fenders, as there is often rust on top of eprons and likely the need of a small welding session. and the other side is likely corroded too.

also I'd change the brakes lines, they are corroded and its way more easy to do it when you have the space.

 

[Jeff73Mach1]

I like to use phosphoric acid. Apply it, let it sit 30 minutes, wash it off. Repeat until all rust is gone. It will leave a white residue behind, that you will need to wash and scrub off of the metal before painting. It will not remove paint. It will not work on greasy metal. Wipe down surfaces with paint prep before priming and painting. It is the main ingredient in most rust removers and can be bought cheaply at Lowe's/Home Depot in the paint department.

 

[Fabrice]

+1 on jeff's post.

I did not insist on the degreasing part while its very important before you apply these chemicals.

Jeff is right: It will not work or a just a little on greasy metal.

 

[Carolina_Mountain_Mustangs]

I would agree with pegleg on the blasting. Since it is not external sheet metal blasting is the best way unless you are going to dip strip the entire body in a huge tank. You should wash all the oil and grease off everything before you blast and be ready to phosphate coat the raw steel immediately after you blast. Will flash rust in seconds if humid.

If you do spray the POR products be sure you have a fantastic breathing mask. Their material reacts with moisture to cure and if you breath it in will coat the inside of your lungs and harden immediately, NOT GOOD. I do use POR in areas I cannot get 100% of the rust off but also use their phosphate to treat before hand. I see people saying they cannot get it to stick but I have never had an issue. With any paint job prep is the key. Any oil, grease, silicone will cause you sever issues in the end.

There are people that can come to you to do the blasting and some use a dustless process but will not remove rust that well. NEVER sand blast exterior sheet metal it will be so warped you will never get straight. If you soda blast exterior sheet metal it is very important to treat the surface to kill the residue of the soda or it will ruin your paint.

Working on one of these cars always turns into a snow ball for sure. If you want to do a great job you take the entire car apart, tag and bag and make hundreds of pictures and start with a bare body shell. A professional job like that will be from $85,000 to over $100,000 for a perfect ground up restore and then it will sell for $30,000, lol.

I do use molasses on parts that can be removed and will fit in the 275 gallon tank I have. It removes all rust like inside the reinforcements under the hood. You can actually pour POR inside and get into the seams and seal it up but takes a big tank.

I have one 72 vert that was dip stripped in a huge tank then dipped in phosphate tank to prevent flash rust. Etching primer and then normal body work. There is no perfect way to attack rust it is in many places that you cannot get to.

You need to look under the dash at the bottom of your cowl. If you have holes and leaks you might as well stop and address that also. The SNOW Ball grows for sure.

David

 

[andy72]

Thanks everyone for the ideas...Great information from all...

Bottom line, I have some work to do.

I de-greased with oven cleaner...Now to try some of the mentioned rust removal methods

 

[Jeff73Mach1]

Keep in mind any chemical used will have to be neutralized and removed before painting.

Residue left in seams can seep out and damage paint otherwise. Use enough product to do the job, but don't overdo it, you can always apply more late if necessary

 

[NOT A T5]

I pretty much wire wheeled the entire body on my 71. It took a lot of time and effort but it was worth it in my opinion.

 

[Fabrice]

@andy72

I would not use oven cleaners. These leave a protective layer behind. Go for something like aceton or thinner.

If you use acid, once done use plenty water before let dry. If you can't use much water where the car is, fill a bucket of water with 1 or 2 spoons of kitchen soda to balance the Ph, flush with that first then pure water.

@NOT A T5

Respect!!!

 

[Carolina_Mountain_Mustangs]

I pretty much wire wheeled the entire body on my 71. It took a lot of time and effort but it was worth it in my opinion.

OMG you must have too much time on your hands. That is a bunch of wire brushing for sure.

D

 

[keiths71]

I'd say pretty much everyone has you covered. Kleen Strip prep and etch is also a great phosphoric acid product,about 20.00 gal. at home depot etc. Keep it wet, use some elbow grease rinse or wipe dry with damp rag. Also excellent for soaking parts over night. It doesn't leave the residue as bad as ospho . Also works on your concrete! Any restoration shops that I have recommended this stuff to have used it since. I would use epoxy primer next, etch primer would work as well. Just don't put any polyester putty or filler directly on etch primer.

 

[Pegleg]

I pretty much wire wheeled the entire body on my 71. It took a lot of time and effort but it was worth it in my opinion.

How many man hours did it take? I have to tackle my interior and want to bring it to that standard

 

[Pegleg]

My engine bay took around a week with a wire wheel