Fiat Tipo rusty sills

Whilst I was fitting an alarm to my Tipo at the weekend, I came to remove the lower trim panel over the sill. Unfortunately, it came off with the screw still in much to my surprise, and upon looking down I noticed a large
hole on the inner sill where the screw had come from :( The strange thing is the outer sill is still rock hard, did Fiat not galvanise the inner sills?
Next question, how on earth do I go about repairing it?
Hellraiser..........>
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Well most go for the glass fibre loaded resin in a tube, if the hole isn't too big. A lot depends on how acessible the hole is, if it is accessible from underneath then a welded patch is the other option. Next important thing is to find how and where the water is getting in. Finally any repair needs waterproofing, multiple coats of Hammerite seem quite good, they have to be applied within so many hours of each other, but in this heatwave each coat dries quickly.
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This could be much worse than you think. The rust you see could be penetrating from the outside in. I came across a small hole on the outer sill and when I removed some of the rubberised coating, the rust extended along the sill, especially around the seam between the floor pan and the underside of the outer sill.
The sad reality is that it appears Fiat still use crap steal but put a coating of zinc in an attempt to improve the cars durability. I have seen exposed steel on cars such as BMWs that does not rust to anywhere near the same extent, even without any protective coatings.
Put the car on ramps and use a screwdriver to check for perforated panels along the seams. The rust proofing will apear fine, so use some force to press through it.
If it is badly rusted, you need it welded - you cannot use fibreglass. Small holes can be repared with fibreglass, however.
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