Is not sanding a rusted rock chip but rather using rust stopper good advice when touching up the paint?

[R826583]

I have around six stone chips on my Polo, two of which appear to have rusted. I have been planning to buy a touch up pen (from: www.cartouchuppaint.com.au) to prevent further rusting or damage to the paint. The advice given to me was to not sand the rust on the paint chip (which is only a few millimetres wide) and to rather apply a rust stopper. The website sells a bundle with the rust stopper pen + metal primer pen + paint pen (found here: www.cartouchuppaint.com.au/buy/product/ ... 2-tupw-cat). Is this good advice or should I rather use a very small sandpaper disk (a few millimetres wide) to manually sand away the rust then prime + paint over it?

[iichel]

any rust that you'll take of with sanding will be profitable. the rust stopper is a chemical compound that reacts to the rust and has a limited capacity.
my advice would be to carefully sand it as good as you can, and then apply the rust stopper.

[R826583]

That was my initial feeling that physically removing the rust would be advantageous. I’ll make a super tiny sanding disk using a hole punch and a toothpick to sand out the rust. Will it matter if the rust stopper goes on the bare metal? I imagine that I will be able to sand until I reach the pure metal beneath the rust. I don’t think it will matter if the rust stopper does contact the pure metal. Either way I’m keen to get rid of these chips!

[2226]

For sanding, use a pencil with an eraser. Cut small disc of sandpaper and glue it to the end of the eraser. You can then twist the pencil to do the sanding. This will also feather the ends of the chipped paint and probably give a much nicer finish.

Rust converter usually seems to convert the top rust layer, but that depends on how thick the rust is and how well the converter penetrates.
For a paint chip I'm sure that rust is purely superficial and rust stopper/converter will get in there, but I'd rather remove as much of the rust as possible anyway.

Sand it back a bit until you see some metal then use the rust stopper/converter to get the small rust pits left behind. It'll be acid so will etch the surface a bit and act like a primer.

[amer6R]

The issue with you using the rust converter just on top of that, that the rust usually bleeds around that area under the paint.
You can use white vinegar after sanding to convert the rust and take it off. you can soak a tissue paper with vinegar, and stick it to that spot. leave it 5-10 minutes than use a Scotch-Brite to clean any dust deposits. then wash with water, dry, antisil and prime. for best results use dtm primer. (direct to metal)

If you are to use rust converter, then apply it leave it for 24hrs then paint over it.

[R826583]

I’m hoping that the rust is localised to the one spot and that it hasn’t spread under the paint. I’ll find out when I start sanding hopefully. Why would I use vinegar rather than rust converter?

My current plan is to sand using some sandpaper on the end of a pencil down to pure metal -> clean the metal site ->rust converter (24hrs) -> primer (let dry) -> colour coat and maybe a clear coat if I can find one.

[R826583]

What has happened with my comments! Typical Australian internet I can’t see a way to delete the duplicates.

[amer6R]

vinegar is faster, you dont have to wait 24hrs and it also converts rust.
It basically makes the rust wash away, like when you are hand washing plates after dinner.
You can use both methods.

[R826583]

Ok I will give it a go! Thank you.