text: Mechanical seals of boiler feedwater pumps often show signs of electrical corrosion. The relative movement between the sliding ring and the stationary ring provokes static charging which is not diverted due to the very low conductivity of the boiler water (below one micro-Siemens per cm [μS/cm]). Within short periods of operation – in some cases, only a few hundred operational hours – pieces having the size of fingertips break off from the sliding and/or the stationary ring and cause rapid increases in leakage current. Diamond-coated (DLC) mechanical seals avoid this problem and extend durability remarkably.