Yes this is normal for an old car that's hasn't been kept in "garage queen" conditions. On my rear trailing arms I noticed that they were unusually thick arms, thicker than the pics I had in the manual, so I poked one with a scredriver and a thick layer of dried clay and dirt cracked and dropped off! it must have been at least 1 cm thick, encrusted right around all the suspension bits...
Until it cracked it looked like old suspension arms and joints and was cammoflaged perfectly. A whole heap of prodding later and I had enough gunk to fill have a bucket with dirt!!!
Needless to say, I'd go over the whole car with a scredriver and start poking. If it's there in the hinges, it's got to be covering other hidden bits and pieces too like it was on mine. The more you remove, the merrier
