Numerical analysis of cathodic protection of a Q355ND frame in a shallow water subsea Christmas tree

This study develops a 3D model of a Christmas tree using cathodic protection technology and conducts numerical simulations on the Q355ND framework of a shallow Christmas tree. The boundary element method is employed for modeling, examining the distribution of protection potentials under varying corrosion layer breakage rates, anode numbers, and positions. The influence of sacrificial anode parameters on the cathodic protection effect of the Christmas tree is also investigated. The findings reveal that when the breakage rate of the anticorrosion layer reaches 35 % during Christmas tree operation, the sacrificial anode fails to provide complete protection. However, if the coating breakage rate is 10 %, reducing the number of anodes by six can still achieve a protection potential of −850 mV. Thus, it is imperative for Christmas trees to maintain a corrosion protection layer breakage rate below 35 %. Beyond this threshold, sacrificial anodes exhibit minimal effectiveness in preserving their integrity.