Four coin. inhibitors were used to avoid pptn. of CdSO4 and SrSO4 after mixing of incompatible water from oil industry with seawater. The tests were carried out according to a developed method at 70 degrees C under pressure 50 bar, at flow 2 cm(3)/min and for 50 min. For 2 inhibitors, a min. concn. 50-60 ppm was detd. at which easy brine flow for 50 min was possible. For 2 other inhibitors, even the increase of their dose to 1000 ppm did not protect the mixt. against pptn.