Hello there
So getting ready to tackle the n/s rear lower rust problem
I tried earlier this year to do a rust cure filler repair but as expected it's back so the next step is to cut out the rot and mig a piece in .
My question is what else do I need ,
I've have or will shortly
1 a mig welder
2 snips
3 angle grinder - with grinding and cutting discs
4 galvanised spray paint ( for behind the panel)
5 filler
6 primer and paint/lacquer
7 masking paper and tape

What I have not got yet is steel plate as I am not sure which thickness is required
So your help will be much appreciated

These photos are from my last repair , and if the permanent repair works good I will post a step by step

well I addressed lots of similar examples on minis when i was younger and learnt that rust usually starts on the inside where you can't see it and what are seeing now is 'the tip of the iceberg'.

you might find that once you hit that with the grinder that the rust extends much further round the arch and along the horizontal section than the picture shows so you will be faced with the quandrary 'how far do i go removing this rust?.

there will also be moisture in the joint between the two panels which will start attacking your workmanship as soon as you're finished!

it's a difficult shape to weld patches onto and the heat from welding will likely affect otherwise sound paint leaving a significant area to fill / paint afterwards.

in addition, when you have finished fixing that section rust will pop up elsewhere.

pretty sure thats not structural so I'd say don't use the mig:

1) use the grinder to remove paint and rust 30mm all around any visible defects
2) use a chisel etc to knock the affected area a few mm below the finished height
3) drill a few holes about 3-4mm here and there to make a key for the filler
4) scrape out as much rust as you can from front and rear
5) heat the area with a hot air gun to dry it out as best as you can
5) put on the filler / paint etc and finish the outside
6) (important) drill a hole somewhere that you can squirt some waxoil / wd40 in behind the repair to slow down further corrosion

Plus (if considering welding), you have all the AV electronics just the other side of that panel, these would all need to come out. If you can remove the air vent behind all of that you will see the extent of rust on the inside too... .
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dexion7@yahoo.com wrote:

well I addressed lots of similar examples on minis when i was younger and learnt that rust usually starts on the inside where you can't see it and what are seeing now is 'the tip of the iceberg'.

you might find that once you hit that with the grinder that the rust extends much further round the arch and along the horizontal section than the picture shows so you will be faced with the quandrary 'how far do i go removing this rust?.

there will also be moisture in the joint between the two panels which will start attacking your workmanship as soon as you're finished!

it's a difficult shape to weld patches onto and the heat from welding will likely affect otherwise sound paint leaving a significant area to fill / paint afterwards.

in addition, when you have finished fixing that section rust will pop up elsewhere.

pretty sure thats not structural so I'd say don't use the mig:

1) use the grinder to remove paint and rust 30mm all around any visible defects
2) use a chisel etc to knock the affected area a few mm below the finished height
3) drill a few holes about 3-4mm here and there to make a key for the filler
4) scrape out as much rust as you can from front and rear
5) heat the area with a hot air gun to dry it out as best as you can
5) put on the filler / paint etc and finish the outside
6) (important) drill a hole somewhere that you can squirt some waxoil / wd40 in behind the repair to slow down further corrosion