Petrochemical equipments made of austenitic stainless steel are often used in the environment of acetic acid solution. Premature corrosion failure led by acetic acid solution containing Cl− or Br− occurs in service. In the present paper, corrosion behavior of AISI316L austenitic stainless steel and SAF2205 duplex stainless steel in acetic acid solution containing Br-ion was studied by measuring the corrosion weight loss and Potentiodynamic anodic polarization curve. Effects of temperature and Br− concentration on the corrosion behaviors of AISI316L and SAF2205 material were investigated. The research results show that the corrosion rate markedly increases and pitting potential rapidly decreases with increasing temperature and Br− ion concentration. The pitting resistance of SAF2205 stainless steels is superior to AISI316L. For sensitized AISI316L and SAF2205 stainless steels, the similar rules were founded with increasing Br− concentration; sensitizing treatment will lead to decrease in corrosion resistance. Pitting induced by Br ion preferentially occurred at austenitic boundaries for sensitized AISI316L stainless steels, whereas pitting preferentially occurred at austenitic boundaries, ferrite-austenite boundaries and ferrite boundaries for sensitized SAF2205 duplex stainless steels.
Purpose
This paper aims to analyze the high temperature (200°C) corrosion behavior of 2205 duplex stainless steel in acidizing stimulation solution containing hydrochloric acid (HCl) and acetic acid.
Design/methodology/approach
The corrosion rate of 2205 duplex stainless steel in all kinds of acid solutions was calculated through immersion tests and electrochemical test. The corrosion product composition is analyzed by X-ray diffraction analysis. The element composition and element distribution before and after corrosion were analyzed by an X-ray energy spectrometer. The corrosion morphology of the steel surface was observed by a scanning electron microscope. Both static and dynamic corrosion experiments were carried out at 200°C.
Findings
The results show that 2205 duplex stainless steel has excellent corrosion resistance in low to high concentration acetic acid solutions, but increasing the concentration of Cl− in acetic acid solution will accelerate the corrosion rate. Low concentration HCl solution can cause serious corrosion to 2205 duplex stainless steel. The system of HCl and acetic acid will produce a synergistic effect on corrosion of 2205 duplex stainless steel and accelerate the corrosion. Sb2O3 is a good corrosion inhibitor synergist for high-temperature acidizing stimulation solution.
Originality/value
The amount of HCl that is used in acidizing stimulation is usually determined by the dissolution effect of the acid on the rocks, but for ultra-high-temperature reservoirs, the amount of HCl should be based on reducing the corrosion of oil and gas wells.
The oxide-scale structure and pickling behavior of oxided 2205 duplex stainless steel in the electrolytes containing hydrochloric acid were investigated. The oxide scales mainly consist of two layers: the outer layer is dense Fe2O3, and the inner granular is FeCr2O4 spinel. During the pickling process, pittings form around the boundaries of FeCr2O4 particles or interfaces of two kinds of oxides, which results in that the electrolyte can directly react with the chromium-depleted layer along the pittings to produce an “undercut” effect so that the pickling efficiency is improved markedly. The pickling mechanism was discussed, and the model was established.
Some ways of estimating the values of the intrinsic viscosity of chitosan were analyzed. It was shown that the method of Irzhak and Baranov for estimating the current value of the intrinsic viscosity allows to adequately estimates the conformational state of the macromolecular coil and its degree of swelling.
Corrosion inhibition effect of 1-butyl-3-methyl-1H- benzimidazolium iodide for 2205 duplex stainless steel in hydrochloric acid solution