BWT system has zero impact on corrosion or coatings

31 Dec 2010
RWO’s CleanBallast disk filters

RWO’s CleanBallast disk filters

Bremen-based RWO, in cooperation with a leading European corrosion institute (SWEREA-KIMAB) and the classification society Germanischer Lloyd, has carried out thorough accelerated corrosion studies in treated full-salinity seawater with the CleanBallast ballast water treatment (BWT) system.

RWO has been a pioneer in this field, and thorough corrosion tests undertaken by independent institutes have proved that the CleanBallast BWT system with its EctoSys disinfection technology does not increase the corrosive properties. The tests simulated operation over an approximate entire lifetime of a ballast water tank/piping structure (approx. 40 years).

CleanBallast operates readily in waters with low and full salinity. The natural corrosiveness of those environments differs significantly with, for example, full salinity (>32PSU) being a very corrosive media to common construction materials. It is also well known that larger quantity of active chlorine has further negative effect on corrosion, increasing the wear rate of non-passivated metals, etc.

The disinfection unit ‘EctoSys’ utilised by the CleanBallast system is based on electrochemistry which operates very differently compared to, for instance, conventional chlorination or electrolysis systems using salt water (containing chloride), where a maximum production of active chlorine is desired. Instead, EctoSys produces short-lived mixed oxidants which, together, have a more striking and powerful effect compared to active chlorine. Thus, the EctoSys is not dependent on chloride content (salinity), but produces oxidants directly from the water. The negative effects of active chlorine on corrosiveness can effectively be avoided.

In natural brackish and full-salinity seawater, besides the short-lived oxidants hydroxyl radicals the disinfection unit EctoSys will produce only low levels (up to maximum 2mg/l) of more persistent oxidants, summarised as TRO (total residual oxidants). Being oxidizing agents, such substances in higher concentrations are relevant for corrosive properties of water. TRO will decay via interactions with, for example, dissolved organic matter.

Links to related companies and recent articles ...