An electrochlorinator makes chlorinated water (sodium hypochlorite, NaOCl or "bleach") from seawater or (artificial) brine, using electricity. The chlorinated water is used as disinfectant cleaning agent in a heat exchanger. No other chemicals are required.
When a low voltage DC current is applied to two graphite electrodes submerged in seawater, electrolysis occurs and sodium hypochlorite (NaOCl) is generated instantaneously. This is classified as a non-hazardous chemical although still a very effective disinfectant. The only byproduct, hydrogen, is safely vented into the atmosphere.

Waste water treatment
Oil platforms
Floating production, Storage and offloading (F.P.S.O.) vessels