The near side sill on my 1992 Jaguar XJS was bubbling at the front.   The rest of the sill was still in excellent condition.  I used a 1mm cutting disc on my angle grinder to cut the bad section out and cleaned the rest with a wire brush wheel.

I cut a piece of steel to go in hole and bent it to the correct curve.

The patch welded in.

The finished repair, painted and lacquered.