Rust pitting on body panels

[Luv2Wrench]

All the body panels for my 1913 Metz have considerable rust pitting. The body panels are also very thin (20 or 22 gauge) and rusted on both sides.

Assuming I can get the rust off via electrolysis and/or media blasting, what should I do to correct the pitting and have a nice smooth surface before paint? I am pretty sure that if I sand down there will be nothing left so I am assuming some sort of filler will be involved. Is a building primer enough?

[nickelroadster]

Assuming that your metal is still strong enough, I would use a polyester sot putty which is basically a very fine grained body filler that is slightly easier to sand . Using a filling primer would probably result in still being able to see the pits to a certain extent. If you used a very high quality filling primer like urethane or epoxy it would end up taking much more time than using polyester spot putty.

[msmazcol]

My vote is media blast first. Start with a rust free surface. One good coat of a epoxy primer to establish a good base to build on. We have had good luck with Clausens Z- Chrome rust defender high build primer. While it can be applied to the bare steel we do prefer the epoxy prime first. After the rust defender is applied it will require sanding. This may take care of a large number of your pits. At that point you can apply any style body filler you prefer to finish off the remaining pits. The important thing is to build on a secure, clean base. No matter how you approach it will be a multi step procedure.

[Guest Backyardmechanic]

por 15 would work too

[A by the sea]

You must get the dark spots out of the bottoms of the pits or they can come back even under paint. Keep in mind the chemical treatments such as por15 or other quick coatings do nothing to really to rust with spare O2 in the bottom of the pit.

Sand blasting or electrolytic rust removal will get all the rust.

You then want to consider SPI epoxy paint direct to metal. The epoxy will seal the rust form getting to the moisture and give a very strong bond to the metal. SPI paint has a fairly long recoat window and it is recommended to put polyester filler direct to the epoxy during the recoat window.

Then do a basic level and then filling primer (see SPI paints) to get fully level.

It is important to read all the tech sheets for the products that you are using.

[pacerman]

If if recall from your restoration posts on the forum you recently received some extra Metz parts. If you have a spare fender with an equivalent amount of rust to what you will be restoring, use one brand of paint system and take it through all the steps. I'm familiar with the PPG products but there are a number of systems out there, Dupont, Sherman-Williams etc. I'd try the electroysis first to get rid of the rust in the pits. I've used it and had some success with it. You could also have the parts dipped professionally. That would surely eliminate the rust. I'd be concerned about using an abrasive process on thin gauge metal.

[Guest palosfv3]

Epoxy primer is primarily a filler material and has no rust inhibiting qualities. When repairing heavy rust pit damage to a steel surface a zinc based 2 part primer is recommended to be appied to all bare metal before the application of any primer surfacer. This is a must do step and is listed in many paint companies technical refinishing manuals . Several paint manufacturers also suggest cleaning the bare metal panels with a metal conditioner before the application of any primer. This is a step that has often been forgotten in todays as well as yesterdays repair shops.

Some self etching primers dont recommend metal cleaners as a preparation step before applying the etch primer. Read your data sheets for the correct proceedure as each paint manufacturer has a slightly different process for application.

I have been to many paint training seminars over the years put on by many of the big name paint companies and all emphasize the importance of this step in the process for the best results in minimizing the return of rust on a metal surface.

[Rusty_OToole]

You might consider electrolytic rust removal or molasses. These methods are less destructive of fragile parts than media blasting and do kill the rust. There are recent threads on both methods.

[Luv2Wrench]

Great input from everyone.

I am going to use the electrolysis process to remove the rust, then a phosphoric acid etch, then the SPI epoxy paint, filler and then paint.

I will be sure and go through the technical lit on the products to make sure I get all the steps correct.

As mentioned, I do have many extra body parts so I will have the opportunity to test.

Thanks again for the great input!