Door sill rust

[Borbus]

I've noticed on my '10 Mk6 there is rust on the front door sills on both sides. On the driver's side there are some that are clearly caused by scuffing, probably from shoes etc. But on both sides there is a spot much further back that couldn't be caused by driver/passenger scuffing but probably by the door itself. Here is a picture of it on the passenger's side where it is the worst:



I started to address the driver's side scuffs before with touch up but it looks like this will need a fair bit more work. I'm thinking sanding down to metal, then a rust converter? Then primer? Then touch up paint? I guess because it's on the sill I won't have to make such a stellar job of it. And if the scuffs which are more in the middle look really bad I might get some door sill protector thingies off ebay.

Anyone done this before?

[SRGTD]

The area of corrosion looks as if it’s on the sill directly below the B pillar if that’s the front edge of the rear door on the right hand side of the picture.

From memory (it’s over 4 years ago since I had my mk6 so I could well be wrong ), there’s a rubber strip / seal that runs along the bottom of the doors. If a small sharp stone or other similar piece of debris has ever been lodged on the narrow flat section of the sill, then when the door’s been closed, it’s possible that a stone could’ve been pushed into the bottom of the B pillar by the rubber strip / seal and penetrated the paintwork down to the metalwork.

As the corrosion looks quite advanced in that area - it looks as if the metal has been eaten away quite badly at the top of the area of damage - I wouldn’t leave it too much longer before getting it repaired, otherwise it’ll only get worse.

It’s years ago since I tackled any corrosion on a car’s bodywork - it would’ve been in the late 1970’s on an old Vauxhall I owned at the time . You may find when you’ve removed all the loose and bubbling paint that the area you’re left with to repair / repaint is quite large, but with any job like this, preparation is key so spend plenty of time on the preparation stage.

You’ll need to make sure you remove all the loose paint and rub down the exposed rusty metalwork to bare metal with appropriate grades of wet and dry paper. Use plenty of water when rubbing down, and ensure the edges of the existing paintwork are feathered into the area to be repainted so there’s no ‘step’ between the existing surrounding paint and the area to be repainted. I’d also be treating the bare metal area with a rust converter product to ‘kill’ and remaining corrosion and then I’d use a car body filler to fill any small hollows or areas where the corrosion has ‘eaten’ into the metal. Rub down the filler once it’s hardened with appropriate grades of wet and dry paper so it’s smooth and level with the surrounding metalwork - again using plenty of water.

You should then be ready for repainting. If you’re having to paint out in the open, pick a day when it’s not windy! I’d recommend using aerosol (rattle) cans - not applying the paint by brush - to ensure a smooth finish. Mask up surrounding areas well to avoid paint overspray, and apply paint in thin, light coats, allowing plenty of drying time between coats. I’d also recommend not spraying right up to the edge of the masking tape, otherwise you’ll have a ‘hard edge’ between the new and existing paint when you remove the tape. Leave the repainted area for a few days and then polish the repainted area and surrounding paintwork to blend the new paint into the existing surrounding paint. Apply a couple of coats of wax or sealant for protectIon.

Good luck with the repair! 

[Borbus]

Yeah, that's the front edge of the rear door. The funny thing is the exact same area is scuffed on both sides, but hasn't rusted anywhere near as badly on the driver's side. So I doubt it was cause by a stone but rather the door seals themselves. The seals are kind of doubled up in that area so would rub more on the paintwork.

Thanks for the advice. I'll be giving this a go soon. My last car had rust around the rear arches which always looked bad but I never considered trying to do anything about it as it seemed such a daunting task. But since this is only in the door sill I think I could tackle it. Also since it's the door sill it has built in edges so less blending to attempt.

Would I need to use primer at all if I'm using a rust converter?

[SRGTD]

Would I need to use primer at all if I'm using a rust converter?

I would, as it will provide a good surface for the colour coat to adhere to.

[barrym381]

Take it to Vw ask them to sort it under the 12 years corrosion warranty although rust will always come back

[SRGTD]

I don’t know how successful the OP would be claiming in successfully claiming for their corrosion under VW’s corrosion warranty, which in 2010 was quite restrictive as it only covered through-rusting from the inside of a panel to the outside. Details of VW’s corrosion warranty from a 2010 Golf brochure;

12-year Body Protection Warranty.
The internal body sections and panels of the Golf are covered against rusting through from the inside for 12 years. Naturally, the Golf must be cared for in compliance with the operating instructions. Please consult your authorised Volkswagen retailer or repairer for full warranty details

The OP’s corrosion looks as if it’s the result of the paintwork being damaged on the surface of the sill panel and rusting on the surface, rather than from the cavity inside the sill. No harm in taking it to VW and asking them though - nothing ventured, nothing gained as the saying goes, although I wouldn’t be surprised if they declined to make good the corrosion..

VW don’t seem to have a very good track record of honouring corrosion warranty claims - quite a few cases on various forums over the years of the front wings rusting on Passats and mk5 Golfs  - either as a result of the foam support pads between the inner and outer wings becoming permanently waterlogged and causing the wing to rust, or the edge of the plastic wheel arch liner rubbing through to bare metal on the reverse side of the wheel arch flange. Many of these claims were either denied or only a partial contribution from VW - with them often citing that the car doesn’t have a full VW service history (what relevance is a full service history to a corrosion issue?), corrosion is the result of an external influence or - in the case of the plastic wheel arch liner rubbing through the paint - corrosion being caused by a ‘mechanical defect’ .

Although, as said above, no harm in making a claim - the worst they can do is to decline it.

[barrym381]

I’ve claimed on this warranty 3 times now once with my s3 Audi and I had both my mk5 gti done wings sills and a tailgate all free of charge u just need to be firm with them

[Borbus]

I forgot to post an update for this. I repaired this last summer pretty much how SRGTD said!

First I sanded everything down as much as I could, then I applied some Hammerite Kurust. It goes on like milk and goes black when it's cured:



Then I masked everything off ready for spraying primer. I saw somewhere a tip that if you roll the paper like you won't get sharp lines that are easy to see. I didn't mind the sharp line at the bottom because it goes with the panel crease, though:



Then I sprayed some automotive etching primer:



That black bit is just some dust that landed after it dried.

Then I used Hycote Tornado Red acryrilic spray: https://www.amazon.co.uk/Hycote-Volkeswagen-Tornado-Touch-Aerosol/dp/B008CE64T2



I'm quite pleased with it. It doesn't look perfect by any means, but who looks that closely in the door sill? When I was doing this job I did think all of this would be hidden when the door was closed, but actually when just the primer was on loads of grey primer was visible on the sill with the door closed! But still, it looks fine and you'd never know it's there. Hopefully I won't have to do this in any more visible places, but if I do have to it's not that hard and looks loads better than rust.

A year later it does have some tiny bubbles under it but still feels solid. I reckon it will be fine now.

[SRGTD]

@Borbus - that looks a pretty good job. I remember from the days of owning older cars with minimal rust protection back in the late 1970’s I regularly did rust repairs to keep them looking decent.

Keep an eye on your sill repair - the rust can sometimes come back even if you do a thorough job with good preparation. If it does ever resurface (hopefully not), then it’s easier to deal with if you catch it early.