Preventing rust on bare metal

[05gt]

I'm planning on finally doing some body work and fix the trunk floor in my fairlane over the winter months, but have a question on preventing rust. Seeing as it will take me a couple of months to complete all the work, what is the best way to keep rust from forming on all the new metal untill I'm ready for some primer? I seen online some guys said to apply a coat of phosphoric acid, and then sand it with a DA to get it off before primer and and body work, but what are some tricks you guys have used on long term exposed sheet metal? Also debated weld through primer? Any thoughts would be greatly appreciated. Thanks!

Mark

[Ford Blue blood]

Phosphoric is your best bet.  It is used to "pickle" metal, used extensively in metal shops and fab shops.  The only other real option is to clean the bare metal really good and prime with self etching primer or epoxy primer.  Simply putting metal prep on it will only slow down the eventual red stuff.  If your shop is dry there should be only a light "flash" rust on the bare metal and it will clean off with 80 grit and a DA.

Weld through is great stuff, works well and will not blow out your welder with spatter and dirt globs.  It really is the only option to keep the inside of panels clean when you can't get to them after they are welded up.

[RICH MUISE]

Actually a very complicated question, with a variety of answers that would be correct depending on your particular application. Also you will find a vast difference in the approach and materials used by different bodymen..you have to decide which is best for you. You asked...here's my opinion:
A lot of what to use depends on where you are using it. The weld thru primer is good as Bill said for the mating surfaces of welded panels that you don't have access to after welding. Beyond that I wouldn't use it as it is not the best base for topcoats. I've only seen weld-thru primer as a rattle can option and I'm wondering if that's why you were asking about it. If you don't have spray equiptment I'd seriously think about aquiring some soon, but if you need a  primer solution in a rattle can, I use mar-hyde self etching primer for touch ups and small parts. It's the best quality primer you'll find in a rattle can..downside is it's about 18. a can.
Phosphoric acid (I use por-15 Metal Ready) imho, is an absolute must for bare metal, new or old. It will give a little added protection while it's waiting for paint, but a lot of that depends on the humidity where you live. If you live in a humid climate you want to get primer on as soon as posible, but it needs to be epoxy primer..all others are more porous and moisture could seep thru. IMHO the phosphoric stage, before and after, is probably the most the most crucial of all the different steps as far as being done correctly...I'll continue this in the next window

[RICH MUISE]

My body rebuild project, btw, took 5 years, so I had pretty much the same issues as you. Fortunately I live in a low humidity area or things may have had to been done differently.
You mentioned trunk floors....the interior panels and most of the underside areas on my car have no primer at all! Yes, that is correct...and should be a good solution for you as well in those areas. After my bodywork was completed in each smaller area, I prepped the metal with the phosphoric and applied por-15. The Por-15 is brushed on, takes about 4 hours to dry and, imho, gives the best long term protection for rust prevention. Por-15 is not used on any surfaces that will get final appearance topcoating such as the outer surface of fenders. It can be sprayed, but brushing is actually in this case the best way to go. The phosphoric acid is actually an excellent base for the por-15 and does in fact help it's adhesion. The phosphoric does not need to be da'd before application of por-15 (it does have to be da'd if using anything else other than por-15). Brushing will not leave brush marks, and can be applied very heavily on seams..it will actually flow between the panels..
The downsides to por-15: short shelf life after opening...buy only small cans. It's expensive, but it covers very well and small cans cover alot. Ask about the 6 packs of 1/2 pint cans..that's why they package it that way. If you buy a quart can, I can almost guarentee you'll lose more than 1/2 of it before you finish the can. The other downside to por-15..it's difficult to get other topcoats to stick to it without sanding, and believe me you don't want to sand this stuff aside from the fact it will interfere with it's metal-encapsulating qualities. 
05GT...check your pm's...I can give you alot of help and advise on things I learned the hard way..but way too long for a post here...I'll send you my phone #'s and if you want you can call for a lot of info.
Rich

[shopratwoody]

I've used phosphoric acid on several projects  including a complete body. Works good. I think I just used water
to wash the parts and the prime and paint. Try not to breath the stuff. Get it cheap at a home depot or such.

[05gt]

Thanks for the replies fellas......appreciate it as awlays! Rich, I may give you a call sometime this weekend and bend your ear for a bit. Seem's like you have alot of good info and lord knows I can use some!! I do have some spray equiptment and a compressor, but wasn't sure how etch primer would do if I ended up doing some additional welding down the road. Anotehr downfall is I live in ohio, so we usually have relativly high humitiy from time to time. I figure it'll take me 5-6 months to get done with all the odds and ends that I need to do, so i figure in that time frame, I'll have a little rust to contend with. Glad to hear some good reviews on por-15 as well. Had seen that stuff and debated on using on some hidden places on the car. I'll have to check with summit racing on the price since its only about 30 min from me.

[RICH MUISE]

I've used phosphoric acid on several projects  including a complete body. Works good. I think I just used water
to wash the parts and the prime and paint. Try not to breath the stuff. Get it cheap at a home depot or such.

I'm guessing different manufacturer's products have to be handled differently. I believe Por-15's Metal ready is envoirementally friendly..you can rinse parts on your grass with no harm, and very little vapors. Also por-15's will interfere with adhesion of primers if it's not da'd...you can't just rinse it and shoot primer over it.
Por-15 should be able to be found in your local body shop supply house and at larger swap meets. also www.por-15.com Por-15 products have a very low retail markup, so you will find little or no difference in pricing from one vendor to another. Living in Ohio, you may have a problem with the appearance of the dried finish with por-15 as it is humidity sensitive in the drying stages.
Call anytime..try my cell phone first.   Rich

[shopratwoody]

I prefer the chemical name, not the manufactures

[RICH MUISE]

Not sure what you meant by that.

[Zapato]

pretty simple Rich, often you can buy a product a lot cheaper than when someone decides to market it to a specific target group in a fancy container. Example At work we used to buy a tin of Lanolin to assemble close tolerance parts, small tin of that costs over $100 bucks, the almost identical product is available in every farm store in a green tin to treat cows teats for under $10-. I've used it for years at home with the same results. Never on my teats.

Bag Balm is not just for udders....................

Zap-

[RICH MUISE]

Hey Buddy..how ya doing? I understand the generic thing, the point I was trying to make is different manufacturers manufacture similar products, and sometimes they need to be handled differently. That was the reason I specifically mentioned the Manufacturers name with the particular problem I had run into knowing that other brands may not have the same characteristics...Whatever Ron was using he didn't think had a need to be da'd, but I wanted to make others aware that some of it does.
Hey Zap..somebody offline was telling me how cool my channeled coupe was! I had to tell him it was yours...I guess I could have just keep my mouth shut and taken the accolades for all the work!  Rich

[Zapato]

finally found the product I remembered reading about   Gibbs Penetrating Oil   check it out its incredible stuff and can even be painted over.

Zap-

[05gt]

I'll check into the gibbs as well. Thanks again fellas!