Serious rust prevention questions, help me save my mk3

[Chaingun]

I'm currently in the process of trying to restore the wheel wells in my mark 3, it has been a long and time consuming process already, and i don't want to have to keep redoing my work. My problem is this, i can make the patch panels, and weld them in and grind it all down so that it looks good, but even after sandblasting and priming everything it's still starting to rust through the primer again.

What i really need is a fool proof way to stop it from rerusting, this car won't ever see a winter again so salt isn't an issue. My plan currently is to clean up the rust again with a wire wheel and sand paper (blasting is just so messy) and then treat all of the metal with a metal prep like thishttp://www.halonmarketing.com/mall/Rust%20Away%20&%20Metal%20Prep.php it will etch the metal and leave a zinc phosphate coating that should help. Secondly i need to do something more permenant. I had thought of POR15 but it is notoriously hard to work with (not to mention toxic)and probably won't work for the outside of the car due to it's inability to take a primer well. The other alternatives are Epoxy primer, or this master coat silver primer. http://www.masterseriescoatings.com/index/primer/ has anyone had any experience with similar products that they can recommend? Once the wheel wells are primed i had planned to clean and dry them well and then roll on truck bed liner for a lasting protection. Any ideas, criticism and especially help is greatly appreciated as I want to do this job right and keep my MK3 out of the junkyard.

 

[phatbimmer]

I dunno if this is of any help but google POR15

 

[Chaingun]

I have, and I've already discounted it as an option for the exterior panels due to it's inability to take a primer without a tie in coat and even that isn't a guarantee it will adhere well, i don't want it to roll into the body shop this winter to get new paint then a year later have it bubble off because the primer didn't adhere well.

 

[supra1008]

I would also like to know how people have personally handled this?

 

[phatbimmer]

I have, and I've already discounted it as an option for the exterior panels due to it's inability to take a primer without a tie in coat and even that isn't a guarantee it will adhere well, i don't want it to roll into the body shop this winter to get new paint then a year later have it bubble off because the primer didn't adhere well.

my bad dude I just re read your post and I saw u already thought of POR15 lol

 

[Canuckrz]

I wouldn't even waste your time if you don't intend on media blasting.

 

[sylquebec]

Look like you did not paint it?! primer is porous and will retain water. paint it and it will not rust.

 

[Chaingun]

Too early for paint, I can't do it until this winter, I'm replacing both front fenders and I have a lot of cancerous steel to remove and replace on the passenger side yet, I did not realize primer would retain water to that degree, still I would rather not risk a 1500 paint job without ensuring it won't rust through in a few years that's why I'm interested in the treatments I mentioned earlier I know the metal etch is a good starting point due to the phosphate coating it leaves behind, and it is an alternative to media blasting inside the car, I can do that again but I would rather not. Does anyone have experience with either epoxy primer, mastercoat, or even por15 (I'll use the tie in coat if needed) I want the best results something i will never have to redo Edit, also, due to the fact that i can see some of the welds had started to rust, should i take out the parts i've welded in, treat them, then reweld them in? again i want this done so it will last 20 years or more. I don't care what it looks like inside the wheel well nobody looks in there, and almost everything external is underneath either the bumper or trim. again time and effort are not an issue, results are.

 

[planemos]

I noticed once that all my 20+ year old toyota trucks never rust out on the front frame. And it is because that part is always covered in grease oil and grime. If you don't want to use POR15 then possibly some wax or grease might work. The inside of my mkiii's quarter panels all had wax/grease on them (probably from factory).

On the other hand. P0R 15 has other things to go with it. They make primers too n stuff. I used just P0R 15 on my airbagged truck. It held up real nice unless the surface of it got damaged. I dragged my truck on the ground. It's strong stuff but it can't resist the weight of the entire vehicle scraping on it. Also on another spot I didn't let it dry and drove it in the rain on a gravel road. Once the surface of it gets damaged it is possible to peel off huge sections of it. My advice to a guy using P0R 15 is to follow the instructions, apply it in the directed temperatures, and let it dry completely. I still believe that if you get a full surface covering of P0R 15 with no imperfections(it's really not that hard just don't get it on your hands) then it will hold up very very well. Plus it is designed to work over rust as well as prevent further rust damage. Which is good because it is pretty much impossible to sand off ALLLLL the rust 100%

 

[89soup]

You want a self-etching rust prohibitive primer... I used to use one on bare metal and I cannot remember the name of it right now... It was a green substance you could just wipe onto bare metal if you were going to be storing it for a short time before priming. A short time turned into a year before i had primed it and it was still clean.

 

[Daugherty_3]

You want a self-etching rust prohibitive primer...

I second using a self etching primer. stuff does wonders. I etch all my panels and it stops it from rusting.

 

[Daugherty_3]

double post.

 

[Chaingun]

Well i spent some time on the phone with mastercoat and por15 customer service today, and after some thought i'm going with the mastercoat. On top of the primer which according to the data sheets can withstand anything por15 can, and they have a product that seems to be very similar to the wax like coating that was used by toyota already. it can be thinned a bit and sprayed on interior panels with something like a wand sprayer, check it out. http://www.masterseriescoatings.com/index/inner-panel-protector/ gonna order some of that and the silver base coat (it's brush on) and the metal prep and i'll report back afterward. after i cut the wheel wells back out and treat them i'll get them reinstalled and hopefully get on with the restoration.

 

[planemos]

Wow that seems like the better choice. P0R 15 is sensitive to UV light I guess mastercoat isn't. Good job!

 

[eraezer]

As far as I know you can't use putty on top of etching primers.
I'm using 2-comp. epoxy primer and that seals it up good.

 

[Chaingun]

hoping for as little putty as possible, it makes sense that putty wouldn't stick well to etched panels due to the zinc coating. that mixes with primers and paints but body putty would be too thick to absorb it. i'm willing to try anything out while i get the patches ready, but i'm fairly certain i'm going to get good results from the encapsulating primer i ordered, weld through primer first, two coats of mastercoat, then the interior panel sealer once it's all welded together. some questions for the masters here. panels that are not quite flush with each other... should i cut them back a bit and put patch between the old panel and the new one or can they be stretched out a bit to mate together? the few seams the better i think.