What would be the best way to stop this rust and stop it from spreading?

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1973 280 - Sold
1980 300SD - Sold
1982 240D - Stolen
1988 300E - Sold
1989 260E - Sold
1989 560SEL
1994 E420 - Sold
1997 E420
2005 CL500

It's my understanding that the rockers rust from the inside out. So it may be they are worse than they look.

You might be able to clean up those spots and spray the inside of the rocker with a rust preventative to slow the progression and get several more years out of them.

I'm sorry to say that that is also my experience - grind off as much of the rust as you can. If you're not too keen on using a grinding wheel an angle grinder with a wire brush attachment is more forgiving. Then go for some sort of rust treatment "system".

I've been using POR15 and KBS products. These both use a water based degreaser, then a zinc solution rust killer, and a pretty good paint for over the top. This paint won't come in the colour to match your car though so you'll then have to treat it with a tie coat primer and then the normal undercoat / colour coat / clear varnish (if applicable for your colour coat). Lots of work to get it back looking like new...

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!