Corrosion x2. This is the same crap that was in my SDL's original radiator. Corrosion like that comes from lack of maintenance, coolant that was left in there WAY too long and the corrosion inhibitors broke down and quit doing their job.

No wonder this radiator was so much heavier than the new one. Probably about a 50% weight gain from all the extra crap it's carrying around in the tubes.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]