Rust pitting, to patch or not to patch?

[evan9eleven]

Hi everyone!

New to the bodywork forum, but I do all my own mechanical work on the car. After 10 years of ownership I finally decided to strip it down for rust repair and a full glass out respray. I am doing all the rust repair myself, and it will be up to the bodyshop to make everything look pretty at the end.

The car has very little rust, except for a few of the common places: windshield corners, fender/tub/cowl joints, and where the upper and lower B-pillars meet.

I should mention that I have a TIG welder and decent skills using it.

My noob question is as follows: how bad does rust pitting need to be to justify cutting out and patching an area? As an example, in one windshield corner there are no pinholes, but quite a lot of deep pitting (see pics.) I can’t grind all of it away or the area will likely get too thin. However, I definitely don't want to have more problems in a few years. I'll patch if I have to, but this type of fabrication is new to me and I'm not well equipped to make complicated or curved pieces.

All advice welcome!

[ChrisHamilton]

What's in the pics, media blast it then use a quality epoxy primer. You don't want to grind away rust as it will just thin everything in that area. Media blast then look at the condition of the panel. Very thin, holes etc. require patching. Poke around with something like a sharp pointed end tool of some sort (words are escaping me ATM). If you can poke through then replace. If everything seems solid then you are probably good. Exception would be when you have deep pitted rust in areas. Then replacement is an option.

What I see in those pics doesn't approach replacement level. Actually looks pretty good. You do want to media blast it though. That is the best way and really the only viable way to do it and remove all the rust. (there are exceptions but I mean DIY)

You can get a "spot blaster" very affordably. The time you save versus sanding, wire wheel, etc will pay for it ten fold. You don't need a huge compressor to run one of the small spot blasters either.

Zendex spot baster is a good one
https://www.google.com/search?client=firefox-b-1&sca_esv=596256598&sxsrf=AM9HkKnDt4bkb4gsRfHLhv0j A2fSvSSJjQ:1704577295737&q=zendex+spot+blaster&sa= X&ved=2ahUKEwiDkdGh3cmDAxXaMVkFHVWoAEYQ7xZ6BAgME AE

TP Tools has a good one to.
https://www.tptools.com/Speed-Blaster-and-Hot-Spot-Spot-Blaster-Kit,7206.html

Those would be the only two I'd recommend. Stay away from the Chinesium knockoffs.

[BwshGulbleSheep]

Originally Posted by ChrisHamilton

Poke around with something like a sharp pointed end tool of some sort (words are escaping me ATM).

Awl

[evan9eleven]

Thanks for the tips!

I'll see about getting a media blaster.

[Dpmulvan]

Those spot blasters are junk and a waste of $100 bill. It will take you 3 days using that POS. Blasting without at least 12cfm is fruitless and without dry air forget it. You’ll spend more time unclogging the thing than blasting.

[evan9eleven]

Good to know! Other suggestions for getting the rust out of the pits then, before cleaning and going at it with epoxy primer?

There are no areas I can poke through in the windshield corners, and just one pinhole another spot on the inner fender which I will weld up.

[pottsalot]

Ospho is an acid type option to rid the rust. Hard to tell by the pictures how deep the pits are. Check out a product called All-Metal if epoxy won’t fill them in….. Easy to work with . Great for car body work as it will not let base metal rust under it like bondo does.

[Conda Green 71t]

It would be REALLY nice to not have to cut open that section of the car. I think that providing there is decent thickness remaining in the metal right there leaving as-is would be my choice. I do agree that media blasting is the best way to clean it [pending whatever equipment you choose to buy for that job]

In regards to you noting that you can TIG weld I would say that that is the neater way to do it for small patches versus using the MIG.

[ChrisHamilton]

If you do use Ospho, make sure you neutralize it before applying epoxy. Otherwise the epoxy wont adhere.

To neutralize you would simply re-wet the treated area with Ospho, keep it wet with Ospho for 10-15 minutes, taking care not to let it dry. You can use a wire brush or scotchbrite pad to help remove some of the crud while doing this. After the 10-15 minutes simply rinse with water thoroughly and quickly dry. It is now neutralized.

Same procedure would apply to any phosphoric acid based product. Epoxy and acid films don't work well together. Often if epoxy is applied over a phos. acid treatment that hasn't been neutralized properly it will simply peel/tear off after the epoxy sets up.

If one is ever in doubt always defer to what the manufacturer of the paint product going over an acid treatment says rather than what the acid treatment manufacturer says. Very important.

[ChrisHamilton]

Originally Posted by pottsalot

Ospho is an acid type option to rid the rust. Hard to tell by the pictures how deep the pits are. Check out a product called All-Metal if epoxy won’t fill them in….. Easy to work with . Great for car body work as it will not let base metal rust under it like bondo does.

USC All metal and the Evercoat Metal2Metal is simply ground aluminum in a polyester filler base. It's body filler. That's all. It's a gimmick type product designed to look like lead. It was originally marketed to be used on A and B pillars of American cars when a quarter panel or roof skin was replaced. Lead was used there by the OEM's and those two fillers were marketed as a replacement for lead. It's not a product that will stop rusting of metal under filler.

Epoxy applied first to bare metal then any filler work over epoxy is the modern and best way to apply filler. Mercedes has been requiring that any repair involving filler be done over epoxy since the mid 90's. All OEM's recommend that process now. Epoxy first then filler will last many times longer than filler over bare metal. Adhesion is greatly improved as well. Really the only way filler should be used on anything of value or importance.

[962porsche]

Originally Posted by ChrisHamilton

USC All metal and the Evercoat Metal2Metal is simply ground aluminum in a polyester filler base. It's body filler. That's all. It's a gimmick type product designed to look like lead. It was originally marketed to be used on A and B pillars of American cars when a quarter panel or roof skin was replaced. Lead was used there by the OEM's and those two fillers were marketed as a replacement for lead. It's not a product that will stop rusting of metal under filler.

Epoxy applied first to bare metal then any filler work over epoxy is the modern and best way to apply filler. Mercedes has been requiring that any repair involving filler be done over epoxy since the mid 90's. All OEM's recommend that process now. Epoxy first then filler will last many times longer than filler over bare metal. Adhesion is greatly improved as well. Really the only way filler should be used on anything of value or importance.

Chris you're 100% correct!!!!
I was going to say the same thing but I'm so tired of pointless debates.

[evan9eleven]

Thanks for all the input guys.

I will be applying epoxy primer first, anywhere I'm down to bare metal. The pitting isn't too bad, and for the most part stands up to being poked with an awl except in one fender area, which I've already patched.

Anyone have experience with Evaporust? I'm sure I'm opening up a can of worms by asking that, but it doesn't hurt to ask.

[962porsche]

Evapor-rust is a fantastic product I have used it countless times restoring motorcycles with fuel tanks that are rusted inside. but in no way would I even think about using it for what this topic is about.
personally I don't like rust treatment , rust converters and such !
I'm a firm believer in a situation like this with rust in the corners of the windshield fillers to spot mid blast the rust down to clean metal. then epoxy prime it if you have a few pits you wanted to fill skim it with a quality body filler spray a little build primer on it and your done.
little hand held spot blasters are very low cost and so is blasting media.

[ChrisHamilton]

Originally Posted by 962porsche

Evapor-rust is a fantastic product I have used it countless times restoring motorcycles with fuel tanks that are rusted inside. but in no way would I even think about using it for what this topic is about.
personally I don't like rust treatment , rust converters and such !
I'm a firm believer in a situation like this with rust in the corners of the windshield fillers to spot mid blast the rust down to clean metal. then epoxy prime it if you have a few pits you wanted to fill skim it with a quality body filler spray a little build primer on it and your done.
little hand held spot blasters are very low cost and so is blasting media.

Yep. Totally agree. Really the only effective way to do it.

[evan9eleven]

Thanks for the tips everyone! The spot blaster worked lik a charm.

[Bill Douglas]

Wow. that looks good Evan.

I've had good luck with this stuff. It's a rust converter (phosphoric acid I guess) and the good thing about it is it's a clear epoxy. A few coats and it appears to be water proof, oxygen proof etc. Then a light deglaze, primer and the top coats.

[evan9eleven]

Originally Posted by Bill Douglas

Wow. that looks good Evan.

I've had good luck with this stuff. It's a rust converter (phosphoric acid I guess) and the good thing about it is it's a clear epoxy. A few coats and it appears to be water proof, oxygen proof etc. Then a light deglaze, primer and the top coats.

Thanks Bill, I have a rattle can of the Brunox stuff, and I used it after sandblasting the battery box area. Worked like a charm and made for a nice primer layer.