the older style frames used copper based anti seize lube.. well you were supposed to. many never did and the chemical solutions of salts and aluminum with alloy bolts caused oxidation. when the bolts do come out... it's white powder corrosion.. do not breathe that and wear gloves. Nasty stuff.
Once you get the bolts out put em in a bucket and pressure wash them, clean up good. You can get crafty with a longer bolt, cut off the head, into cordless drill, some copper lube and in out kind of thing if the frame threads are loaded with corrosion. load up the threads with the copper lube on the cleaned up bolts and put em back together with new white washers and top washers and cleaned up bolts. Good to go and leak free.
