Moparts

Sealing rust pits

Posted By: mopar 394

Sealing rust pits - 01/12/10 03:54 PM

I am stripping a couple of fenders and there are a couple of small rust pits that were under the paint. What should I put over these to seal or neutralize them before I spray the epoxy primer or will the primer seal them?

Attached picture 5729923-100_1993.jpg
Posted By: domingo

Re: Sealing rust pits - 01/12/10 05:53 PM

wirte brush em until all rust comes out then use resu neutralizer such as ospho or phosphoric acid and repeat the procedure until there is no dark reisdue....then prime.
Posted By: domingo

Re: Sealing rust pits - 01/12/10 05:54 PM

from the looks of the sheetmetal surface I can tell you have been using an orbital sander....the sandpaper lays flat and wont reach the pitted cavities which are lower. You need to use a wire disc on a drill.
Posted By: domingo

Re: Sealing rust pits - 01/12/10 05:55 PM

also dont prime over the ospho residue....wire wheel again, degrease and then apply the primer.
Posted By: Neil

Re: Sealing rust pits - 01/12/10 07:07 PM


Put a stiff wire wheel in a drill and keep the rpm really slow. If you go full throttle the rust glazes over and then gets even harder to remove.

You can also use a dremmel tool with a sanding disc or small grinding bit and dig it out that way.

Clean the area with some ppg metal prep after your done.
Posted By: elitecustombody

Re: Sealing rust pits - 01/12/10 10:22 PM

take a trip to harbor freight or pick up a small spotblaster gun from tool truck and blast that junk out, don't waste your time with wire wheel,because you will never get all of the rust out, when done,metal wash and spray etching primer followed by epoxy primer,or shoot epoxy and skip etching primer,it'll work either way
Posted By: DAYCLONA

Re: Sealing rust pits - 01/12/10 11:28 PM

Quote:

take a trip to harbor freight or pick up a small spotblaster gun from tool truck and blast that junk out, don't waste your time with wire wheel,because you will never get all of the rust out, when done,metal wash and spray etching primer followed by epoxy primer,or shoot epoxy and skip etching primer,it'll work either way








Exactly, the only way to address this issuse
Posted By: QuickSilver

Re: Sealing rust pits - 01/12/10 11:44 PM

I agree with these guys. Blasting and sealing right away is your best bet. I personally don't like to metal prep the area since it leaves residue down in the pit forming salts that you can see with a magnifying glass and these will blister your nice new paint. We found this out the hard way when I was doing high end Model "A" Fords. The fuel tank is part of the cowl and dash assy and they receive full paint and the tops of the tank around the fuel cap are usually really rusted. Of course in the AACA judging criteria the cars must be all laquer but we did use epoxy primer under coats. We never had anymore problems with rust pit blisters.Good Luck.
Posted By: domingo

Re: Sealing rust pits - 01/13/10 12:28 AM

If you can get a blaster it wouyld be tyhe best. But it will make a mess....

Also be careful not to use too much pressure or a non appropiate blasting media or you can risk warping the panel. Blasting straight at a 90º angle will stretch the metal and make the panel bulge and oil can. Best way is blasting at an angle lets say 30º.

If you want to try and wire wheel it also dont use too much speed as others said...too much speed and you can also heat the sheetmetal and make it warp.
Posted By: domingo

Re: Sealing rust pits - 01/13/10 12:31 AM

Dremel works great for the super small pits.
Posted By: mopar 394

Re: Sealing rust pits - 01/13/10 12:38 AM

Has anyone had good luck with a small spot blaster. What brand and model do you use?
Posted By: elitecustombody

Re: Sealing rust pits - 01/13/10 01:57 AM

I like the Speedblaster, works great, most tool truck guys have them, I wouldn't sweat any warpage,the affected area is pretty small to cause any damage
Quote:

Has anyone had good luck with a small spot blaster. What brand and model do you use?

Posted By: domingo

Re: Sealing rust pits - 01/13/10 06:16 AM

Quote:

I like the Speedblaster, works great, most tool truck guys have them, I wouldn't sweat any warpage,the affected area is pretty small to cause any damage
Quote:

Has anyone had good luck with a small spot blaster. What brand and model do you use?





Regarding warpage: Its not the size of the affected area that matters really, it's where its locatedon the panel. Try to get those pits off the center of a 68-70 Charger decklid -large flat area very prone to oil canning-and Ill bet you will get warpage...and tahts on a panel with a shut underbrace. Not a pretty sight-

Try spot blasting a Challenger door near the center bodyline....you should be OK.

Speaking in general I try to avoid blasting on outer sheetmetal as much as possible. and just use it when its only NECESSARY if its on a spot where it wont cause warpage, or if badly pitted and blasting is necessary well yuou better have access to fix the warpage afterwards.
Posted By: elitecustombody

Re: Sealing rust pits - 01/13/10 01:30 PM

I prefer blasting and obviously it all depends on who is doing it,how well they know the equipment,air pressure and angle,but fine media with low pressure and quick passes will not warp anything even in the middle of 1 square mile of sheetmetal.
Posted By: domingo

Re: Sealing rust pits - 01/13/10 08:15 PM

Quote:

I prefer blasting and obviously it all depends on who is doing it,how well they know the equipment,air pressure and angle,but fine media with low pressure and quick passes will not warp anything even in the middle of 1 square mile of sheetmetal.



If he is asking how to remove rust pitts, I bet he doesnt know what's the proper thechnique for blasting a part without damaging it. Nor whats the proper equipment, or safe blasting distance, angle, pressure, kind of media, etc. From what I see on his post I assume he is tackling the job by himslef. I doubt he will be able to fix a wavy panel if he damages it.

There are several ways to tackle a job, and if you get the same results I guess its just a matter of preference or convenience given each particular circumstances.

I know I have removed rust pits like those using a wire brush on a handheld drill, using a dremel too. I have used phosphoric acid based metal wash and then have wire wheeled the pits to get rid of the metal wash residue and then I degrease it with whichever is the reccomended grease removal agent for the paint line Im gonna be using and then I shoot the epoxy primer.

I did this to my Challenger 8 years ago. It had LOTS of those rust pits on the roof because it used to have a vynil top. Rust pits on other places as well.

I have yet to see 1 single blister on it....and we have around 75% humidity here in Lima all year round. I dont keep it on a climate controled garage. I cant see one single spec of rust on it yet.

Blasting is a great way to solve this problem, but there are other ways which dont require much knowledge which will do the job as well. You dont have to buy expensive equipment or make a mess if you dont have a dedicated blasting booth.

You can also dip the doors and E coat them for that matter.

In the end, what we are after is good results, there are several ways to get it done. I know what I said above works, Ive done it myself with good proven results. Ive also blasted with great results and no warpage as well. Ive also messed up some sheetmetal by blasting it....so I prefer not to take chances on the more delicate body panels....but thast just my way of doing things. Its what works for me!

Attached picture 5732518-PaseoV8076SMALL.jpg
Posted By: bbodybill

Re: Sealing rust pits - 01/13/10 09:05 PM

I must be missing something here... My first thought would be naval jelly(to remove rust) and then something to neutralize the jelly???
Posted By: SSAAHemiFan

Re: Sealing rust pits - 01/13/10 09:21 PM

Naval jelly works great !

FWIW - I have used wire wheel's, spot blaster, metal prep , and naval jelly to remove rust - all methods work well.

Be sure you know ahead of time what primer you are going to use!

Some are NOT compatible with use of a etching product.
Posted By: elitecustombody

Re: Sealing rust pits - 01/13/10 10:28 PM

domingo,we all have our opinions and if your wire wheel method works for you, great,but I know that wire wheel will never get deep enough into the bottom of the pit,you have to admit, some of those pits look like wood eaten by termite and some are so deep that only blasting will remove all the rust,by wire brushing, you cover up the rust most of the time,and it seems OP has air compressor,so picking up a Speedblaster and hitting few spots will not make a big mess or cost alot of money, removing old paint and sanding creates just as much of a mess as blasting few small spots, I do this everyday for a living, so I'm speaking from 20 years experience not from one project.

Now, let OP do whatever he choose and lets stop arguing
Posted By: domingo

Re: Sealing rust pits - 01/14/10 12:37 AM

Im not arguing. I have done a few cars myself as well.

Of course my advise is vaild if it works. dont take my advise as gospel...if the pit has certain characteristics where the wire wheel wont work...then Id move on to the blasting....Id NEVER leave any rust specs on there...but I always like to start off mild b4 going WILD on everything I do.

oh well, guess you get my point.

If this is not clean enough, I dont know what would it be...this is the hood for my 69 original HEMI Charger. 3m abrasives pad on a drill and the infamous fine bristle wire wheel. I dont see any rust specs on it. Not a single wavy spot as well. get my point? why blast it if its not necessary?

It makes me cringe when I see people blasting good nice original outer sheetmetal panels to remove paint and or superficial rust. Same deal with high speed sanders that leave deep scratches on sheetmetal that not even a light primer coat will fill up.

by the looks of the sheetmetal finish on mopar 394 seems he used an orbital sander...thats That wont damage, nor heat up nor warp sheetmetal.

Attached picture 5733033-015.jpg
© 2024 Moparts Forums