Electrochemical Behaviour of High-Temperature High-Lithium Bromide Solutions on Low Alloy Steels

Electrochemical behavior of low alloy steels with high temperature and high concentration of lithium bromide solution Guo Jianwei, Liang Chenghao (College of Chemical Engineering, Dalian University of Technology, Dalian 116012, Liaoning, China) The electrochemical behavior of Mo42- for low alloy steels. The results show that Mo42 as an anode corrosion inhibitor can promote passivation, blocking the anode and cathode reactions. When the concentration of N%Mo4 reaches 200 mg/L, the active dissolution of the low alloy steel can be effectively suppressed. Addition of Cr and Ni elements to low-alloy steels improves corrosion resistance, while AI elements deteriorate corrosion resistance. The Mo element participates in the film formation process, and the coordinated action of Cr and Mo elements enables the A steel to pass through at a lower Na2Mo4 concentration.

Lithium bromide solution is a strongly alkaline corrosive medium. It has strong corrosion to carbon steel, low alloy steel, stainless steel, copper and its alloys, which are often used in bromine coolers. Corrosion not only affects the service life of the equipment, but also the hydrogen generated by the corrosion reaction will destroy the pressure balance between the high pressure cylinders, generate rust, and block the piping and nozzles to reduce the thermal efficiency and even cause shutdown. In addition, galvanic couples and residual stresses caused by contact with various metals can exacerbate the broccoli machine's etched holes and breakages, which can have catastrophic consequences. The study of carbon steel in lithium bromide solution shows that simultaneous use of OH and Mo42 as corrosion inhibitors can effectively inhibit the activity of dissolution. However, there are few reports on low alloy steels. This paper discusses the effect of boiling Na2Mo4 concentration in 55% LiBr+0.07mol/LLiOH solution on the electrochemical behavior of low alloy steel.

Table 1 Chemical composition of low-alloy steel (wt. Working area of ​​the electrochemical sample is 10mmX10mm, non-working surface coated with silicone insulation, and connected with copper wire. Soaking the sample is 30mmX20mmX2mm. The sample is polished by water sanding paper to 800 rinse with deionized water, degreasing the propylene glycol, and drying after use.

The immersion test was carried out in a stainless steel case, an autoclave (50 mm in inner diameter, 65 mm in height) containing PTFE. The sample was deoxygenated with high-purity gas in a 90 mL test solution for 1 h. The system was kept in an AT-S13 incubator at a preset temperature for 200 h. After the sample was removed, 50 C of 3 mol/L HCL and hexamethylenetetramine were used. The corrosion rate was determined by the weight loss before and after the sample was washed for 10 min. Its calculation formula is: density of material, 7.87g/cm3; A: surface area, cm2; T: test time, h. Electrochemical test under three-electrode system, using HA-501 potentiostat, reference electrode is The Ag/AgCl electrode and the auxiliary electrode are Pt electrodes. The experimental medium was configured with 55% LiBr+0.07mol/LLiOH and different concentrations of Na2MoO4 solution using analytical reagents. Heating to boiling (145°C) After the corrosion potential (Ecorr) is stabilized, the cathode and anodic polarization curves are measured at a scanning speed of 20mV/min. The anode is polarized and the potential corresponding to 100M/cm2 is identified. Determine the polarization resistance Rp steel polarization curve for the pitting potential Eh. 20mV (45°C) (/cm 2) Scanning speed 5mV/min a) Anodic polarization b) Cathodic polarization is determined by strong polarization Fig. ± Tuffian's slope ba, bc of the anode and cathode, calculated to obtain corrosion rate