What's the proper plumbing term?

[tewald (Terrill Ewald, CPI, MD# 31310)]

What’s the correct term for the stuff around the drain nut? Corrosion?
Scum? left from prior leak.

[mlarson (Michael Larson, WI Lic. # 1672-106)]

What’s the correct term for the stuff around the drain nut? Corrosion?
Scum? left from prior leak.

Evidence of past leaks

[rcloyd (Russell Cloyd, KY LIC #166164)]

Waste material on drain nut, evidence of past leakage.

[lkage (Larry Kage, CMI)]

Evidence of past leaks

Agree…