Surface Rust Removal... What Works Best?
 

I just received an old Porsche part today that has a lot of surface rust on it. I intend to strip and re-paint this item but I need to know the best way to remove the rust? The part has a lot of small crevices and is built of thin sheet metal. I plan to use POR15 on it once I get the surfaced cleaned up. Does muric acid work or how about navel jelly?

I'd start with Naval Jelly. I recently saw some at Pep Boys that was in a spray bottle, so it is probably a bit thinner and will work its way into the crevices.

POR stands for Paint Over Rust, right? You really do not need to remove all the surface rust if you are planning to paint with POR, it actually adheres better to irregular / porous surfaces, I believe...;-)

Re: Surface Rust Removal... What Works Best?
 

I presume you meant Muriatic Acid (hydrochloric acid). I would not use this acid on metal as it is quite aggressive., The advantage of naval jelly (phosphoric acid) is that the rust reacts with it 10 times faster than the base iron. That way the rust goes away but the base metal is intact.

Naval jelly is nice in that it will stay where you put it. Something like Rust Mort is the the same thing but is more runny. You may find this better for your application.

Good luck.

What part is it?

also there is a product called ''Extend". It comes in both a spray bottle and a brush on. I don't believe any of these items remove rust though. They neutralize rust, stop the cancerous spreading. One of the best ways to remove it is with a medium grit 3M Green Corps roloc sanding disk in a DA or drill motor. It works fast and doesn't eat up the metal if you pay attention to what you are doing. Used them when replacing my front suspension pan to get to good metal in spots. Then come in 2" or 3" sizes, go with the 3" just make sure you get the proper backing disk!

Naval Jelly works well on removing gun-blueing too! How do I know? When I was a kid I thought it would be a good way to clean my brand new Browning BL-22 ..... worked a little too good. :) -- Curt

Just take the part to your local machine shop and have it bead blasted, apply primer then some paint. Bullet proof system!

I say "amen" to the guy who mentioned "Extend" which you can buy at Pep Boys. Sand off the loose part of the rust - Then apply Extend and it works miracles. I've been using it for years. My understanding is that it not only covers the rust, but it chemically combines with the remaining surface rust and metal below to bond to the metal. Bottom line: Rust gone and will never come back. Extend will turn black when it dries. Takes about an hour (or less) to bond.

IMO Mechanical cleaning works well on flat surfaces, but with complex shapes it is difficult to get into the crevices.

I do not fully understand how Extend works other then encapsulating rust. It's still there, just hidden and I guess the manufacturer hopes no more oxygen will get to the part and cause the rust to grow.

Rust Mort, Naval Jelly and the other phosphoric acid based treatments actually dissolve the rust (if you leave it on long enough) and then rinse it fully.

For maximum effect, I would remove what I can mechnically and then use rust mort/naval jelly to get the last bits and followup with POR-15.

SILVERC4S - As much as they would like to to believe that you can Pour it over rust, their directions have you pretreat with phosphoric acid prior to coating. I think they call the product "metal ready", it leaves a zinc phosphate coating. Read their information here: http://por15.hypermart.net/faqmetre.html

CEGERER -- Did you know that "blueing:" IS a form of rust?

as far as the mechanical cleaning in complex shapes goes, that's why I use the 3" roloc green corps disks. They are very flexible around compound curves while spinning!

Extend..........'nuf said.

Sorry to disagree with you, HarryD - But Extend does not just encapsulate the rust - If that was all it did, then it would eventually chip off and the rust would live. It chemically bonds with the rust and the metal below and the rust is gone forever. You should sand off the loose serface rust first, though.

This turned out to be a very helpful post!

The part I’m trying to bring back to life is actually a one piece dash knee pad from a mid 60's 911.

I’ll try using Naval Jelly or something similar to remove the rust as most have suggested.

I’m still trying to figure out the best way to protect the metal after it’s stripped. It needs to be something that won’t come off when glue is applied for the vinyl. The only options I can think of are POR, powder coating, and paying someone to professional spray it.

Now it gets down to cost… POR is the only reasonable option I could think of. Any other suggestion would be appreciated.

OK,

I just looked at the Extend MSDS. It contains 1-5% Formic Acid (an organic acid) which will react with the metal and rust. The balance of the hazardous ingredients are paint compnonents (acetone, Dimethyl ether, and 2-butoxyethanol). Now I can see how it works. :)

Personally, I would want to remove any traces of the acid before I paint to ensure the etching action is stopped fully, but that is just me, I guess. :confused:

This fellow did a pretty nice Rust Product Comparison.

Mr Ruf,

POR 15 is a great product. Just be careful to have it only where you want it. My garage floor is still spoted with the stuff from where I had spattered it 2 years ago. Wears like iron. It also bonds very, very, very well to your skin.