Sorting out the rust in a Mercedes Sprinter

[kamas]

Recently got a Sprinter and noticed a few spots of rust. One area concerns me a bit and not too sure how to tackle it.

There is a bit of rust in the rear wheel arch, in the seam. It's only a few inches long but visible on the outside as well.

What is the best way to get it sorted that does not involve welding ideally?

Was thinking of cleaning the rust out as much as possible, then using Bilt Hamber Deox gel.
This would be followed by either:

1. Jotamastic 90 ALU + U-POL GRAVIGARD on the underside
2. Rust-Oleum CombiPrimer + Rust-Oleum CombiColor

Any one method is better for this particular application? Worried that I will not be able to get 100% of rust out of the seam and Jotamastic will fail.

As an aside, any recommendations for a white topcoat for Jotamastic? Was going to get Jotamastic 90 ALU for its better rust protection and overcoat white on the inside of the van.

 

[fizzy]

Jotamastic every time. Brushed on for that.
On the inside no need for anything fancy - even a spray can - just roughen up the epoxy paint first.
I have a new sprinter on hire - the rust traps on them are awful - even my mates old Fiat van has better protection - so much for German quality.

 

[Domdom]

I would be using a rust converter before the Jotun.

UPOL also do GraviTex which is (allegedly) overpaintable. Cellulose based and goes on nicely enough. Gives good stonechip protection.

 

[octo0072000]

thought sprinters was made in Spain i know the MB100 was so could have changed now

 

[Alan Reynolds]

Sprinters seem a bit notorious for rust. A friend bought a second hand one and because it’s not used much, it seems to sprout new rust spots weekly. On top of that te turbo went, the brakes needed new disks and pads, the front shocks and top mounts need replacing and the power steering rack has now got a lot of slack on one side and needs to be replaced and it has various engine error codes that keep popping up.
On the other hand my 55 plate lwb Iveco in ten years has no rust, needed just the normal tyres and brakes and I replaced the back axle as The whine got on my nerves eventually, even though it had been there since I bought it.

 

[Dcal]

Wire brush in a 4 inch grinder to get rid of the rust and seam sealer you can reach (both sides) then something like Fertan rust remover which should creep into the joint. Let that cure then sand the bare steel with 80 or 100 grit sand paper.
Apply one coat of Jotun 87 or 90A by brush. Let that cure overnight then apply seam sealer over any gaps (both sides) let that cure then another coat of Jotun blended into the "keyed" existing paintwork and then stone chip and /or top coat of your choice.
That should last longer than the rest of the van.

The key thing is sealing the remaining rust, that you can't get at, from moisture and oxygen.

 

[charlysays]

Good old Merc rust, pretty much the only premium vehicle brand to drag rust issues kicking and screaming into the 21st century lol.

Looks like you have caught it at a good time where you can ensure it doesn't shorten the life of the vehicle.

I agree with all above that your best bet is Jotamastic. My favourite is 90 Aluminium winter grade. The standard hardener isn't much use in UK winters in unheated workshops. The alu adds increased barrier effect and more resistance to cathodic debonding. You can use Colad mixing cups to mix it (3.5:1 ratio), use the 7:1 scale then add 10% extra hardener in the thinners column and that gets you 7:2 (same as 3.5:1) near as damn it.

What I found worked best for surface prep was thorough needle scaling with the needles at an angle to the substrate, keep the edges sharp by regularly grinding them flat on a bench grinder when they go rounded- this removes 90% of the rust and gets into the craters too and blasts away unwanted paint and seam sealer and underseal too. Then straight bristle wire wheels at low RPM (I use a cheap silverline right angle air drill), I usually attack from several angles to get good coverage over pitted steel, then key it up with 40-60 grit using mini DA and/ or abrasive sponge pads. The straight bristle wheels are great at getting right into seams and the low RPM prevents them polishing the rust. I usually rake out seams with a pick tool too to get out the worst then get the wire wheel in there. Obviously depends on the tools you have but basically aim for St3 surface prep. St2 is the bare minimum.

I would use a rust killer type product in the seam only, worked in well, then go again with the wire wheel. I use 45% phosphoric acid usually, work it in let it dry in the seam then wire wheel out again, then blast it out with brake cleaner but any good rust killer or converter should do the job. As already said you want to seal that all up well both sides for a permanent fix.

 

[Onthespotwelding]

Sprinters rust worse than transits these days!

 

[knighty]

Sprinters rust worse than transits these days!

better engines!

I'm slowly dumping transits and moving over to sprinters