The invention provides a method for heating a liquid (20) in a heater (100), wherein the heater (100) comprises a heating element (110) and a counter electrode (120), wherein the method comprises (i) heating the liquid (20) in the heater (100) by heating the heating element (110) to a temperature in the range of 120-250° C., and (ii) applying an AC potential difference between the heating element (110) and the counter electrode (120), wherein the AC potential difference varies with an AC frequency (f) in the range of 200-2500 Hz and has an amplitude in the range of 1-5 V, and wherein the liquid flows in the heater (100) between the heating element (110) and the counter electrode (120).