Study on the Surface Corrosion Resistance of Titanium Steel Composite Plate in Simulated Seawater
Titanium steel composite plate combines the excellent corrosion resistance of titanium material with the advantages of high strength and low cost of steel, and is an indispensable structural material for corrosion-resistant equipment such as pressure vessels, chemical reaction vessels, heat exchangers, and petroleum transportation pipelines.
Welding is a key means of manufacturing titanium steel composite plates, and the quality of welding directly affects the service life of the composite plates. The welding of titanium steel composite plates belongs to the category of dissimilar material welding. Currently, commercial titanium steel composite plates in China are mostly formed by explosive welding. Due to the instantaneous high temperature and strong impact force generated by the explosion, there may be welding defects such as impurities, pores, and cracks at the joint interface of the composite plate. In recent years, laser welding using high-energy density laser beams as heat sources has rapidly developed due to its advantages of strong local heat input, small thermal impact range, and good controllability. Especially with laser additive manufacturing technology, melting welding of titanium steel dissimilar materials becomes possible by adding an intermediate transition layer. Based on powder feeding laser additive manufacturing technology, the research team has successfully prepared titanium steel composite plates with mechanical properties that meet the requirements of the national standard GB/T 8547-2019
Request TA2/S30408 titanium steel composite plate.
Titanium steel composite plates are used in harsh environments, and harsh environmental factors can accelerate the failure of the welded structure of the composite plate. Corrosion failure is one of its common failure forms. Once the titanium steel composite plate fails, it will seriously affect the reliability of the equipment and pose a threat to personal and property safety.
Starting from the manufacturing process of titanium steel composite plates, this article studies the surface corrosion resistance of explosion welded titanium steel composite plates, additive manufactured titanium steel composite plates, and stress relieved additive composite plates using a simulated 3.5% NaCl solution of seawater as the corrosive medium.
Experimental materials and methods
There are three methods for comparing and analyzing the corrosion resistance of surface coatings
Titanium steel composite plate.
(1) Annealed explosive composite plate TA2/Q345R;
(2) Original additive manufacturing composite board TA2/S30408 (including Cu intermediate layer);
(3) Additive manufactured composite board TA2/S30408 after stress relief annealing (300 ℃, 4 hours of insulation).
Use a wire cutting machine to cut the electrochemical sample (sample size 5 mm × 10 mm × 5 mm), wash the sample with anhydrous alcohol, and blow dry it. The surface of the non test specimen is brazed to the copper wire, ensuring good contact. Then, the test specimen is placed face down in the cold embedding mold, and finally, epoxy resin is poured into the mold for curing and molding. After demolding, the surface of the sample is polished with 5-20 μ m metallographic sandpaper (from coarse to fine) on a water mill, polished with 1 μ m diamond solution and 0.3 μ m alumina suspension, rinsed with anhydrous alcohol, and dried for later use. Electrochemical performance testing was conducted using an electrochemical workstation (CHI660E) with a 3-electrode system. The working electrode was the titanium layer on the test surface of the sample, the counter electrode was a graphite electrode, and the reference electrode was a saturated calomel electrode (SCE). The corrosive medium is a 3.5% NaCl solution, and the volume of the corrosive solution for each group of samples is not less than 100 mL. Perform AC impedance and polarization curve tests after the potential stabilizes. The amplitude of the AC impedance test is 5 mV, and the scanning frequency is controlled between 0.1 Hz and 10 kHz. The polarization curve scanning starts at 50 mV below the self corrosion potential and ends at 1.5 V, with a scanning speed of 5 mV/s. Finally, use an electronic balance to weigh the sample before and after corrosion, and calculate the corrosion rate using the weight loss method.
