Effect of Dissolved Oxygen Concentration on the Microbiologically Influenced Corrosion of Q235 Carbon Steel by Halophilic Archaeon Natronorubrum tibetense

The influence of dissolved oxygen concentration (DOC) on the microbiologically influenced corrosion (MIC) of Q235 carbon steel in the culture medium of halophilic archaeon Natronorubrum tibetense was investigated. The increase of DOC from 0.0 to 3.0 ppm was found to strengthen the oxygen concentration cell by promoting cathodic reaction. Meanwhile, the increased DOC also promoted archaeal cell growth, which could consume more metallic iron as energy source and aggravated the localized corrosion. When the DOC further increased to 5.0 ppm, the uniform corrosion was dominant as the biofilms became uniformly presented on the steel surface. Combined with the stronger inhibition effect of oxygen diffusion by the increased biofilm coverage, the MIC of carbon steel in the 5.0 ppm medium was weaker than that in the 3.0 ppm medium. From weight loss and electrochemical tests, the results all demonstrated that the carbon steel in the 3.0 ppm medium had the largest corrosion rate

Learning a Mid-Level Representation for Multiview Action Recognition

Recognizing human actions in videos is an active topic with broad commercial potentials. Most of the existing action recognition methods are supposed to have the same camera view during both training and testing. And thus performances of these single-view approaches may be severely influenced by the camera movement and variation of viewpoints. In this paper, we address the above problem by utilizing videos simultaneously recorded from multiple views. To this end, we propose a learning framework based on multitask random forest to exploit a discriminative mid-level representation for videos from multiple cameras. In the first step, subvolumes of continuous human-centered figures are extracted from original videos. In the next step, spatiotemporal cuboids sampled from these subvolumes are characterized by multiple low-level descriptors. Then a set of multitask random forests are built upon multiview cuboids sampled at adjacent positions and construct an integrated mid-level representation for multiview subvolumes of one action. Finally, a random forest classifier is employed to predict the action category in terms of the learned representation. Experiments conducted on the multiview IXMAS action dataset illustrate that the proposed method can effectively recognize human actions depicted in multiview videos

Effect of SO2 content on SCC behavior of E690 high-strength steel in SO2-polluted marine atmosphere

Slow strain rate tensile (SSRT) test in a simulated device was employed to investigate the effect of SO2 on stress corrosion cracking (SCC) behavior of E690 steel in SO2-polluted marine atmosphere. Results revealed that SO2 can greatly enhance the SCC susceptibility of E690 steel in marine atmosphere and the SCC mechanism in this environment is a combination of anodic dissolution (AD) and hydrogen embrittlement (HE). The increase of SCC susceptibility was attributed to the formation of a compact rust layer on steel surface that SCC microcracks can initiate from the bottom of cracks in the rust layer consequently. Moreover, hydrogen evolution was greatly enhanced with the increase of SO2 content, and SCC susceptibility increased rapidly as a result

Effect of Alternating Current on Corrosion Behavior of X80 Pipeline Steel in Near-Neutral Environment

The rapid development of energy, electricity, and transportation industries has created a market for steel pipes; however, buried steel pipelines near high-voltage transmission lines and electrified railways often experience alternating current (AC) corrosion at the damaged coating of pipelines; such phenomenon is mostly due to the resistance between the capacitance and inductance coupling, especially for long-distance pipelines in parallel operation. AC corrosion can cause pipeline corrosion perforation and stress corrosion cracking (SCC) in some cases, which has been a vital threat to the pipeline safety. In this work, the influence of AC on corrosion behavior of X80 pipeline steel was investigated in NS4 near-neutral solution by data acquisition technique, electrochemical test, immersion tests and surface analysis techniques. Results show that with the increasing of AC density, corrosion morphology changed from uniform corrosion to localized corrosion with many pits. Under the full AC interference, X80 steel occurred cathodic and anodic polarization which resulted in iron dissolution and hydrogen precipitation. The negative half wave AC would lead to hydrogen evolution and hydrogen induced anodic dissolution, the pits in X80 steel surface present sharp. However, under disturbance of positive half-wave AC, only anodic dissolution occurred and the pitting appeared spill shape and smoothly. Under various AC waveform interference, the corrosion products of X80 steel surface were different. Under full AC wave and positive half-wave interference, the corrosion products were loose, had have no alpha-FeOOH and occurred cracks; however, under negative half-wave AC interference, the corrosion products were denser and contained alpha-FeOOH which has protective effect on substrates

Effect of pH and hydrogen on the stress corrosion cracking behavior of duplex stainless steel in marine atmosphere environment

Electrochemical and stress corrosion cracking (SCC) behaviors of 2205 duplex stainless steel (DSS) of different microstructures in the marine atmosphere environment with various pH values and hydrogen charging current densities were investigated by employing electrochemical measurements and the slow strain rate tensile (SSRT) method. Results indicated that the resistance of 2205 DSS to pitting corrosion deteriorated as the pH decreased, and the susceptibility to SCC improved in spite of the decrease in pH or the increase in hydrogen charging current density. As compared to the microstructure of the as-received specimen, microstructures of the normalized and especially the quenched samples were more vulnerable to SCC

A Modelling Study for Predicting Life of Downhole Tubes Considering Service Environmental Parameters and Stress

A modelling effort was made to try to predict the life of downhole tubes or casings, synthetically considering the effect of service influencing factors on corrosion rate. Based on the discussed corrosion mechanism and corrosion processes of downhole tubes, a mathematic model was established. For downhole tubes, the influencing factors are environmental parameters and stress, which vary with service duration. Stress and the environmental parameters including water content, partial pressure of H2S and CO2, pH value, total pressure and temperature, were considered to be time-dependent. Based on the model, life-span of an L80 downhole tube in oilfield Halfaya, an oilfield in Iraq, was predicted. The results show that life-span of the L80 downhole tube in Halfaya is 247 months (approximately 20 years) under initial stress of 0.1 yield strength and 641 months (approximately 53 years) under no initial stress, which indicates that an initial stress of 0.1 yield strength will reduce the life-span by more than half

Enhancement resistance to microbiologically influenced stress corrosion of Cu-bearing steel against Bacillus cereus

Abstract Microorganisms are notoriously known to cause local corrosion and stress corrosion cracking (SCC), which seriously endangers the materials service safety. Cu can enhance antibacterial function of the material and reduce the vulnerability to hydrogen embrittlement (HE). However, the dilemma of how much Cu content generates the best resistance to microbiological corrosion and SCC arises. Here, we modified the Cu content in pipeline steel to obtain the best antibacterial effect to nitrate reducing bacteria Bacillus cereus and HE resistance. The findings offer a fresh perspective on how to design and prepare a steel that are both resistant to microbiological corrosion and SCC

Comparative study of the SCC behavior of E690 steel and simulated HAZ microstructures in a SO2-polluted marine atmosphere

Simulated microstructures of the typical CGHAZ, FGHAZ, and ICHAZ of an E690 welded joint were prepared with heat treatment at peak temperatures of 1300, 850, and 750 degrees C, respectively. Slow strain rate tensile (SSRT) tests were implemented to investigate the stress corrosion cracking (SCC) behavior of E690 steel and the simulated HAZ microstructures in a SO2-polluted marine atmosphere. Results revealed that E690 steel and its simulated HAZ microstructures all had a high SCC susceptibility in the simulated SO2-polluted marine atmosphere with a combined mechanism of AD and HE. The SCC susceptibility gradually increased in the following order: BM, CGHAZ, FGHAZ, and ICHAZ. The cracking mode of BM and CGHAZ was transgranular, whereas that of FGHAZ and ICHAZ was intergranular. The lower SCC susceptibility of BM and CGHAZ was probably due to the impeding effect of lath bainitic grain boundaries on SCC propagation, whereas the higher SCC susceptibility of FGHAZ and ICHAZ was attributed to the facilitating effect of M-A islands on crack initiation and propagation. (C) 2015 Elsevier B.V. All rights reserved

Effect of Hydrogen Charging on the Stress Corrosion Behavior of 2205 Duplex Stainless Steel Under 3.5 wt.% NaCl Thin Electrolyte Layer

The effect of hydrogen charging on the stress corrosion cracking (SCC) behavior of 2205 duplex stainless steel (DSS) under 3.5 wt.% NaCl thin electrolyte layer was investigated on precharged samples through hydrogen determination, electrochemical measurement, and slow strain rate tensile test. Results show that hydrogen charging weakens the passive film without inducing any obvious trace of localized anodic dissolution. Therefore, hydrogen charging increases the SCC susceptibility of 2205 DSS mainly through mechanism of hydrogen embrittlement rather than mechanism of localized anodic dissolution. 2205 DSS shows a more susceptibility to hydrogen under the TEL when hydrogen charging current density (HCCD) is between 20 and 50 mA cm(-2). The increasing trend is remarkable when hydrogen charging current density increases from 20 to 50 mA cm(-2) and fades after 50 mA cm(-2)