Study On Galvanic Corrosion Law Of Typical Electric Couple In Marine Engineering Equipment Under Simulated Deep Sea

Dissimilar metals were commonly employed in the ocean engineering equipment which was used in deep-sea environment. Inherently, this would lead to galvanic corrosion,destroy the equipment, and even cause the inestimable losses to the national economy and national defense. Studies on the theoretical of the galvanic corrosion occurred in the deep-sea was the base of corrosion control, which contributed to the improvement of design and construction of national ocean engineering equipment, was urgent and important.The objective of this work is to study the galvanic corrosion of some Galvanic Couples(GC) in simulated deep-sea environment at different pressure, temperatures and different dissolved oxygen content through a self-designed device by means of electrochemical techniques, weight loss measurements and microscopic characterization methods. The galvanic couples contain low-alloy steel 907/B10 copper nickel alloy, low-alloy steel907/TA2 titanium alloy, low-alloy steel 921/B10 copper nickel alloy, low-alloy steel921/TA2 titanium alloy, low-alloy steel 907/921/B10 copper nickel alloy, low-alloy steel907/921/TA2 titanium alloy, low-alloy steel 907/921/HDR duplex stainless steel.The results indicated that temperature and dissolved oxygen content have important effects on the couples of the galvanic corrosion. The corrosion rate of low-alloy steel 907 would increase from 0.025mm/a to 0.25mm/a with the pressure rise, while it decreased from 0.20mm/a to 0.14mm/a for 921.The dissimilar Galvanic Couples(GC) in simulated deep-sea environment showed consistency that the galvanic potential was positive when coupled, and then gradually stabilized within 20~40h after negative shift rapidly.For duplex couples, the galvanic current density have a trend of gradually decreasing with the pressure increasing from 0 to 10 MPa expect 921/B10 GC. Both elevated temperature and dissolved oxygen content would aggravate the galvanic corrosion. When the dissolved oxygen content was lower than 10 ppm, the galvanic current density had a linear increase with the dissolved oxygen content rise apparently.For three-phase coupled GC, when the pressure was below 10 MPa, anode creation mainly occurred in 907 of 907/921/B10 GC. The galvanic corrosion rate had little difference between 907 and 921 when 907/921 and TA2 coupled. Anode creation mainly occurred in 921 of 907/921/HDR GC. With the increase of temperature makes all three couples of 907, 921 galvanic corrosion rate increases. The rise of temperature made a contribution to the increase of corrosion rate of 907 and 921 in three-phase coupled GC.