Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Effect of W and Mo on the corrosion behavior of low alloy steels in O2-H2S-CO2 humidity corrosion environment
Zhao, Qing-he (University of Science and Technology Beijing) | Liu, Wei (University of Science and Technology Beijing) | Zhu, Yi-chun (University of Science and Technology Beijing) | Zhang, Bin-li (University of Science and Technology Beijing) | Lu, Song-le (University of Science and Technology Beijing) | Lu, Min-Xu (University of Science and Technology Beijing)
Abstract The effect of W and Mo on the corrosion behavior of low alloy steels exposed to acid humidity corrosion environment containing O2, H2S, and CO2 was investigated using weight loss, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. The results indicate that both addition of W and Mo can improve corrosion resistance of low alloy steels, and the enhancement effect of W is better than Mo. Surface layers are mainly composed of FeOOH, Fe3O4, and small amount of S and Fe2 (SO4) 3·nH2O. Mo and W element in steels can be oxidized into MoO2, MoO3, and WO3, respectively, which can act as corrosion inhibitor during corrosion process. Mo steel have lower corrosion resistance than W steel, because the chemical transformation from MoO2 to MoO3 may form defects inside surface layers, and the smaller molecular mass and volume of MoO3 than WO3 makes MoO3 easier to move in surface layers and lower the resistance of anodic dissolution. Introduction The inner gas in vapor space of crude oil tankers (COTs) contains oxygen (O2, 1~5%), carbon dioxide (CO2, 1~13%), hydrogen sulfide (H2S, 500~3000ppm) and water vapor originating from transported crude oil. Electrolyte film have been observed to form on the backside of upper deck due to the day/night temperature change, and dissolution and chemical reaction of O2, H2S, and CO2 lowers the pH of the electrolyte film. Thus, severe corrosion occurs. Low alloy corrosion resistant steels has been developed by many researchers and steel corporations to provide high service stability and reliability for the upper deck in such corrosion circumstances due to its high economic values and corrosion resistant properties. A small amount of alloy elements, such as Cu, Ni, Cr, Mo, and W, are added into low alloy steels to form a dense and protective surface layers preventing the steel plates from further corrosion. The effect of Cu, Cr, and Ni on the corrosion behavior of low alloy steels in various corrosion environments containing O2, H2S, and CO2 have been reported by lots of researchers, but the effect of W and Mo was rarely reported. The aim of present investigation is to illustrate the effect of W and Mo on corrosion behavior of low alloy steels exposed to an O2-H2S-CO2 humidity corrosion environment.
- Materials > Metals & Mining > Steel (1.00)
- Energy > Oil & Gas (1.00)
- Transportation > Freight & Logistics Services > Shipping > Tanker (0.54)
Effects of chromium and H2S on corrosion performance of 3Cr steel under CO2-H2S environment
Lu, Songle (University of Science and Technology Beijing) | Liu, Wei (University of Science and Technology Beijing) | Fang, Zichun (University of Science and Technology Beijing) | Guo, Yuanyuan (University of Science and Technology Beijing) | Wang, Xuemin (University of Science and Technology Beijing)
Abstract Corrosion performance of 3%Cr steel in CO2 and CO2-H2S environments was investigated using high temperature and high pressure autoclave. Corrosion scales were characterized by XRD, SEM and EDS. The existence of Cr element and H2S both reduced general corrosion rates of 3Cr steel compared with API X60 steel. Under CO2 and CO2-low H2S partial pressure environments, the Cr-rich layer on 3Cr steel played a decisive role in inhibiting corrosion due to the hydrolytic action of Cr and the formation of chromium compound. Under CO2-H2S environment, 3Cr steel still exhibited higher corrosion resistance than carbon steel and would be a promising material option. Introduction CO2 corrosion is a common damage which happens in oil and gas production and transportation frequently [1, 2]. The low Cr alloy steel is suitable for tubing casing and pipeline steels with high corrosion resistance and low cost [3]. Cr element could lead corrosion scale to turn from crystalline state to amorphous state [4] and significantly improve density and adhesion of the corrosion scale formed in CO2 environment [5]. Due to the formation of self-repairable scale [6, 7], the Cr-rich layer played an important role in CO2 corrosion resistance [8]. The CO2 corrosion environment combined with H2S frequently exists in oil and gas industry [9, 10]. Although CO2-H2S corrosion of carbon steel has been studied widely [11-13], seldom studies have been carried out for corrosion process and corrosion mechanism of 3Cr steel in this environment [14]. The corrosion scale of 3Cr steel in CO2-H2S environment should be more complex than that in CO2 environment, and corrosion performance of 3Cr steel in this environment should also be different from that of carbon steel. In this paper, corrosion performance of 3Cr steel in CO2 environment and CO2-H2S environment with two H2S partial pressures had been studied, and API X60 carbon steel was used for comparison tests. The corrosion scales both X60 and 3Cr steels were analysed and discussed, which could help to further apply 3Cr steel properly in CO2-H2S environment.