INTERNAL CATHODIC PROTECTION OF SEAWATERPIPING SYSTEMS EVALUATION BY USE OF COMPUTER MODELLING ANDCOMPARISONS TO EXPERIMENTAL RESULTS

摘要

Cathodic protection is used on seawater piping systems both to control galvanic couplingphenomena between equipments as well as to prevent crevice corrosion initiation at criticalareas.An extensive programme has been undertaken in order to evaluate the use of cathodicprotection on nickel base alloys and highly alloyed stainless steels. A full scale seawater loopmade of alloy 625 has been implemented and cathodic protection parameters such aspotentials and current distribution along the pipe have been measured for variousenvironments including natural seawater and chlorinated seawater. Comparisons between zincgalvanic anodes and impressed current cathodic protection have also been made.In addition to full scale corrosion measurements, computer modelling has been carried outusing the Boundary Element Method software PROCOR. The numerical results have beencompared with the experimental results for a series of experiments and after determining therelevant polarization input data.Experimental and computer modelling accord well and show that the internal protection ofalloy 625 is limited to small distances both in natural seawater and in chlorinated seawater.