海水流速对DH36平台钢阴极保护的影响

Effect of Flow Velocity on Cathodic Protection of DH36Steel in Seawater

利用自行设计的管流式海水循环实验装置模拟在0.20~2.00 m/s流速范围内的阴极保护情况,采用恒电流极化法进行阴极保护,通过电位的变化、电极宏观形貌和钙质沉积层的生成情况评价阴极保护效果。结果表明,流速越大,电位达到保护电位-800 m V(vs Ag/Ag Cl海水)时所需的电流密度越大;而且当流速大于1.20 m/s时,即使电位达到了保护电位仍可能发生明显的冲刷腐蚀;生成的钙质沉积层主要是单层的富镁层,只有电流密度较大时,才会在富镁层上进一步沉积富钙层。

A series of cathodic polarization experiments for DH36 steel has been performed with seawater flow in a range of flow velocities: 0.20, 0.40, 0.60, 0.80, 1.00, 1.20, 1.40 and 2.00 m/s in a pipe flow circulating seawater device. For each flow velocity, at least three different polarization current densities were chosen to perform galvanostatic cathodic polarization for 7 d. The results showed that the current density demand for an adequate cathodic protection(CP) increased with the flow velocity; the potential could be also polarized to achieve-800 m V vs the silver/silver chloride(seawater) reference electrode(Ag/Ag Cl [sw]) when the velocity was up to 1.00 m/s; however when the velocity was above 1.20 m/s, erosion- corrosion probably could occur even the polarization potential has achieved the protective potential; the calcareous deposits formed on the steel surface were most single magnesium- rich layers. Exceptionally, calcium- rich deposits could form on top of the magnesium-rich layer only when a very high current density was applied.