Rear suspension mount corrosion

When I decided to have the frame powder coated on my 1984 Zg1300 I sent it off to the P/ coasters for the usual blasting then black gloss finish the next day I received a call from the guy doing the work that I needed to go to his shop because of a problem, instantly I new that he had blasted through the frame at the suspension mountings, (had this on two Z1100 shafts) sure enough there was a gaping hole, while I was there I told him to carry on and blast both sides on that and the other mount, the blasting cut through the "steel" like the proverbial knife through butter which surprised me as the media used was Aluminium Oxide..
It was a relative easy fix shaping 2mm plate and welding up, just before I finished the last weld on each o poured oil into the "cups " then sealed them.
It is worth checking these areas as they are prone to rottingI forgot to get pics but have attached one of the area I am talking about..

Well I thought I had attached a photograph