Six weeks exposure tests were run with CuNi 70 30 (C71500) and CuNi 90 10 (70600) tubes in a flow
loop with artificial ASTM seawater (pH 8.2; flow rate 0.5 m/s) at room temperature and 40°C in the
absence and presence of 1 ppm hydrogen sulfide. The effect of hypochlorite addition (0.5; 1.0; 3.0 ppm;
sensor controlled) was investigated on tube surfaces i) in the as-received surface condition, ii) after
conditioning with additive-free artificial seawater and iii) after conditioning with artificial seawater
containing 1 ppm bisulfide. The conditioning was performed for 6 weeks at room temperature under
access of air.
On a non-conditioned as-received tube surface the presence of hypochlorite increases the mass loss rate.
The effect increases with the hypochlorite concentration and decreases with increasing temperature
(40°C). Pre-conditioning of the inner tube surface with additive-free artificial seawater is beneficial to
improve performance in the presence of hypochlorite.
The presence of bisulfide in the flowing seawater significantly decreases the corrosion resistance of both
types of CuNi alloys in the as-received surface condition, as well after 6 weeks conditioning with
additive-free and bisulfide containing seawater.