Probing the Anti-Corrosion Behavior of X65 Steel Underwater FSW Joint in Simulated Seawater

Abstract

To detect the corrosion resistance of a friction stud welding (FSW) joint in simulated seawater (a 3.5 wt% NaCl solution), the pulse electrochemical deposition method was used for electroplating Ni coating with different duty ratios (50%, 80%, and 100%) on the surface of FSW joint. The microstructure and surface structure of the coating were observed by micro-spectroscopy and other characterization methods. The corrosion behavior of the coating was analyzed by means of macroscopic electrochemical testing. The local corrosion law of joint surface and coating surface defects were innovatively explored by using micro-zone electrochemical scanning system. The coating characterization results showed that, as the duty ratio continues to increase, the coating surface becomes denser and smoother, and the corrosion products such as Fe2O3, Fe3O4, and FeOOH are generated. The results of macroscopic electrochemical experiment indicated that the coating with 100% duty ratio has the lowest corrosion current density and the maximum polarization resistance. The scanning vibrating electrode technique results showed that the corrosion current density in the defect area is higher than that in the coating area, and the maximum corrosion current density decreases with the increase of duty ratio. The localized electrochemical impedance spectroscopy results indicated that the localized impedance at the welded zone was the largest, and with the increase of the pulse duty ratio, the impedance diffusion in the defect area was decreasing.

Erosion–Corrosion Behavior of Friction Stud Welded Joints of X65 Pipelines in Simulated Seawater under Different Flow Rates

“…Since sea sand on the seabed is not uniformly distributed, it was mixed and stirred in this experiment to deposit the sand at the bottom, preparing for experiments at different flow rates. A 3.5% NaCl solution was selected as the experimental solution, with the addition of sea sand particles with sizes of 0.25 mm, 0.5 mm, and 1.0 mm to simulate their presence in seawater [ 2 ]. The mass fraction of sea sand used in the experiment was 3.5 wt%, and the experimental pressure was 1 MPa at room temperature.…”

“…Due to the growth of the offshore oil industry, friction stud welding has become a popular method for welding underwater pipelines. This technique is not affected by high-pressure environments and produces high-quality weld joints [ 1 , 2 ]. Considerable research has been conducted on the mechanical properties, technological processes, and metallographic changes of friction stud welded joints.…”

“…Considerable research has been conducted on the mechanical properties, technological processes, and metallographic changes of friction stud welded joints. However, due to their relatively weak corrosion resistance, there is a growing need to investigate the corrosion behavior of these welded parts [ 2 , 3 , 4 ].…”

“…Ma [ 4 ] employed friction stud welding to join the stud with X65 steel, and investigated the interrelation among microstructure, microhardness, chemical composition, and local electrochemical behavior in a 3.5% NaCl simulated seawater solution. Ma [ 2 ] innovatively studied the localized corrosion behavior of the joint surface and coating surface defects using a microarea electrochemical scanning system in a 3.5% NaCl simulated seawater solution. The findings indicate that the corrosion resistance at the weld seam is superior to other areas.…”