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Due to the shape of the front of our cars the hood and especially the front of the roof right above the windshield are very prone to stone chips. Easiest thing is to keep up on it with touch up paint before it starts to rust.
 

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For something small like that I don't bother with primer or clear on top. Just use a good touch up paint with a brush. The pens are worthless. My objective is to stop the rust, not make it look good.

My experience has been if I want it to look perfect or close to I'm far better off to spray the entire panel. Way too much work for a touch up job.
 

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Rust converter then touch-up paint.
Rust converter only gets the surface of the rust. It doesn't form some kind of magic seal like they'd have you believe. It must be removed first and then rust converter used to get rid of any small bits that you can't see with your eye and only then painted. It'll come back otherwise.
 

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Sorry for my absence and thank you for the helpful replies!

I sealed the air out using vaseline whilst mulling over what to do.. and my plan is to A) touch up the spots temporarily.. but as I like the car I'm considering B) getting the roof resprayed.

I have spoken to a few a detailers and bodyshops and been advised that if the spots aren't exposed to air, the rust shouldn't progress, at least it will inhibit progress for a long time ie months maybe years, and can be monitored for any bubbling under the paint. It does seem to look worse in the pics than IRL btw.

A) For the touch up I have picked up..

Fibreglass pencil.. to pick back any loose paint
Isopropyl alcohol to degrease
A little polish
Rust convertor.. I see some debate going on here! This is what I've got : Kurust
Professionally mixed paint to match the car colour code (I also have a Mazda touch up stick - but this should be better)
Some cocktail sticks
Quality lacquer..

So plan is scratch out the visible rust with the pencil (yellow area of the spot below), degrease, apply some rust convertor, paint, polish the spiders legs/tracks slightly so they aren't prominent (up to red circle), then liberally apply lacquer to cover in excess of the area of concern.. buff it all up, and shouldn't look too bad. As air cannot reach the rust, I'm told this should hold up for a decent while, according to bodyshops I've spoken to "as long as I keep the car". 🤷‍♂️

Any good? I could of course sand back to the red line..



That said.. I'm likely to go for

B) Roof respray. I've had quotes of £300, £400, £1000+, and £1400 GBP.

The higher quotes were from places that deal with insurers who made a bit of a fuss about removing the sharkfin (seems like you just remove some trim and carefully reach into the headline?), and they also wanted to remove and replace the screen and more. As the screen is not bonded to the roof (correct me if I'm wrong!) and no rust seems to be that near the screen, I don't see that being necessary?

The chap who quote me £400 came recommended by three trusted friends, reckons the window seal can be pulled forward (will that damage it?) and the respray look good as new. I'm inclined to go with him. He actually encouraged me to just touch up as described and monitor so wasn't hustling for work.. but I'm OCD so would like to have confidence the problem is gone for say ..4..5 years. I've been advised by a paint sprayer that it may needs spot sand-blasting to ensure that? Sounds a bit OTT to me..

Anyway.. any thoughts.. ? This will be my first respray if I go that route..

BTW I believe @arathol is correct and it's stone chip X bird poop lime. Personally until the paint is lifted I'm not convinced those 'tracks' are rust underneath.. everybody says it is.. sure.. but can you find a picture of a similarly rusted stone chips? I reckon it's paint stress caused by the lime, that has crackled from the point where the stone chip delaminated it. If you look at paint damage from bird poop it can stress paint without causing rust. I'm probably wrong, but that's my theory atm. Definitely the legs/tracks appeared within 2-3 weeks, and were all under bird muck. Seems like rust would take longer to do that..
You're quite correct on the point of seal it up so no air or moisture gets in and there will be no rust. Good call with the vasoline, it will help. I did something similar with my old car. I wanted one more year out of it and the brake lines and oil pan were all rotting out. Coated them in multipurpose grease, worked great.

Here's the problem. It's nearly impossible to make that perfect seal. You also have to consider the underside of the metal that you can't see also. Even paint is not perfect.

Rust converter products do indeed work if used correctly. They're not meant to simply cover up on top of significant rust and hope it holds. Unfortunately they're usually sold as such.

Por15 is an interesting product but very expensive.

The respray is a great option if you want to pay for it but don't get the cheapest one. Body work is so expensive because it is insanely labor intensive. Something I know from my own experience :) wasted many hours trying to repair rust on old cars!

Bottom line is the rust must be removed and metal properly treated before spraying any new paint on it or you'll be wasting your money.

As mentioned before, if you're only looking to hold it back for a few years and you don't care what it looks like you're already on the right track.
 

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Thank you.. from the 'bottom line' here.. I'm guessing if it were your car you would be sanding back to that red circle at least :)

Another suggestion I've had is to do just that, prime it, sand it, then just wrap the roof. If the car was white I might be keen on that!

I think that would make the car very hard to sell if the need arose...
Well having had similar stone chips go to rust on my car, I stripped the rust, treated the metal, painted with touch up since that's all I had, and then buffed it to feather it in. So sort of yes :)
 
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