MAKING A PATCH

1 If a small area on a wheelarch has corroded, it may be easier to cut out the rot, then weld in a patch. Start with an angle grinder and cutting disc to remove the rotten metalwork.

2 Cut out a clean piece of sheet steel to fit inside the hole. The piece of metal shown here extends beyond the arch, but it will be trimmed in situ after it has been welded in position.

3 Disconnect the battery and make sure you have a fire extinguisher to hand. Tack weld the new patch into position, making sure it remains flush with the rest of the wheel arch.

4 Trim off any excess sheet metal if required – this will make it easier to shape the edge of the patch against the rest of the wheel arch. Seam weld all the way around the patch.

5 Tidy up the weld with an angle grinder to achieve a smooth finish that’s flush with the rest of the wheel arch. You may need to return to welding if you spot any holes or gaps.

6 Protect the clean metal with paint, then blend it into the bodywork with a skim of filler and rub it down with wet and dry paper – repeat until you achieve a smooth finish.

7 Use an angle grinder to clean up the inside of the existing inner arch. This will help to weld the new inner arch to it. Clean metal is essential for good quality welding.

8 Trim the new inner arch, then fit it and secure with vice grips. Shape the top edge into the inside of the existing inner arch using a panel beating hammer.

9 Tack weld the top edge of the new inner arch to the clean metal of the existing inner arch. Use a pry bar or large screwdriver to push the top edge of the inner arch into position.

10 The temporarily fitted outer arch can now be removed. Using an angle grinder, carefully grind off the spot welds to remove the arch. This requires a steady hand to avoid damaging the bodywork.

11 We can now see the new inner arch we’ve just fitted and the remains of the old inner arch. The remains of the old inner arch can be trimmed off with an angle grinder.