Corrosion Mechanism of L360 Pipeline Steel Coated with S8 in CO2-Cl− System at Different pH Values

The corrosion behavior of L360 pipeline steel coated with or without elemental sulfur (S8) in CO2–Cl− medium at different pH was studied. An autoclave was used to simulate the working conditions for forming the corrosion scale, and an electrochemical workstation with a three-electrode cell was used to analyze the electrochemical characterization of the corrosion scale. A wire beam electrode was used to determine the potential and current distribution, and scanning electron microscopy and X-ray diffraction were used to characterize the morphology and composition of the corrosion scale. The results showed that the deposition of S8 on the surface of the electrodes caused serious localized corrosion, especially under acidic conditions. The morphology and localized corrosion intensity index further proved that the deposition of S8 significantly promoted corrosion, especially pitting corrosion. Finally, a novel corrosion mechanism of L360 pipeline steel coated with S8 in a CO2-Cl− environment under acidic conditions was proposed, and we then modeled the theoretical mechanisms that explained the experimental results.

Phospholipids from plant materials as a corrosion inhibitor in oil production

The article presents the assessment results of carbon steel corrosion rate in 15% hydrochloric acid (aqueous solution) in the presence of phospholipids at 60 °C. The corrosion intensity was estimated from the rate of weight loss; the intensity of electrochemical corrosion was determined from the value of the corrosion current density. Phospholipids were isolated from vegetable oil waste. Surfactants of various operating principles were used as samples for comparison and enhancing the additives efficiency. It was found that the use of phospholipids under experimental conditions made it possible to provide protective properties up to 86.5% for phospholipids individually and up to 95% in a 50:50 mixture with a cationic surfactant.

Incidence of Pitting Corrosion Wastage on the Hull Girder Ultimate Strength

The paper focuses on the assessment of the hull girder ultimate strength, combined with random pitting corrosion wastage, by the incremental-iterative method. After a brief review about the state of art, the local ultimate strength of pitted platings under uniaxial compression is preliminarily outlined and subsequently a closed-form design formula is endorsed in the Rule incremental-iterative method, to account for pitting corrosion wastage in the hull girder ultimate strength check. The ISSC bulk carrier is assumed as reference ship in a benchmark study, devoted to test the effectiveness of the incremental-iterative method, by a comparative analysis with a set of FE simulations, performed by Ansys Mechanical APDL. Four reference cases, with different locations of pitting corrosion wastage, are investigated focusing on nine combinations of pitting and corrosion intensity degrees. Finally, a comparative analysis between the hull girder ultimate strength, combined with pitting corrosion wastage, and the relevant values, complying with the Rule net scantling approach, is performed. Based on current results, the modified incremental-iterative method allows efficiently assessing the hull girder ultimate strength, combined with pitting corrosion wastage, so revealing useful both in the design process of new vessels and in the structural health monitoring of aged ships.

Effect of shear stress on the wall of technological pipelines at a gas condensate field on the intensity of carbon dioxide corrosion

The object of the study is a section of the gas and gas condensate collection system, consisting of an angle throttle installed on a xmas tree and a well piping located after the angle throttle. The aim of the study is to assess the impact of the flow velocity and wall shear stress (WSS) on the carbon dioxide corrosion rate in the area of interest and to come up with substantiated recommendations for the rational operation of the angle throttle in order to reduce the corrosion intensity. In the course of solving this problem, a technique was developed and subsequently applied to assess the influence of various factors on the rate of carbon dioxide corrosion. The technique is based on a sequence of different modeling methods: modeling the phase states of the extracted product, three-dimensional (solid) modeling of the investigated section, hydrodynamic flow modeling of the extracted product using the finite volume method, etc. The developed technique has broad possibilities for visualization of the obtained results, which allow identifying the sections most susceptible to the effects of carbon dioxide corrosion. The article shows that the average flow velocity and its local values are not the factors by which it is possible to predict the occurrence of carbon dioxide corrosion in the pipeline section after the angle throttle. The paper proves that WSS has prevailing effect on the corrosion intensity in the section after the angle choke. The zones of corrosion localization predicted according to the technique are compared with the real picture of corrosion propagation on the inner surface of the pipe, as a result of which recommendations for the rational operation of the angle throttle are formed.

МАТЕМАТИЧЕСКАЯ МОДЕЛЬ КОРРОЗИИ ВНУТРИ МЕТАЛЛИЧЕСКИХ ВОДОПРОВОДНЫХ ТРУБ

In water supply systems, one of the most important factors is corrosion of pipelines from steel and cast-iron pipes, an increase in pressure losses, which reduces water flow and increases energy consumption. Excessive corrosion intensity is determined by

МАТЕМАТИЧЕСКАЯ МОДЕЛЬ КОРРОЗИИ ВНУТРИ МЕТАЛЛИЧЕСКИХ ВОДОПРОВОДНЫХ ТРУБ

In water supply systems, one of the most important factors is corrosion of pipelines from steel and cast-iron pipes, an increase in pressure losses, which reduces water flow and increases energy consumption. Excessive corrosion intensity is determined by

Corrosion of Hydrogen Storage Metal Alloy LaMm-Ni4.1Al0.3Mn0.4Co0.45 in the Aqueous Solutions of Alkali Metal Hydroxides

Corrosion of pristine AB5-type metal alloy LaMm-Ni4.1Al0.3Mn0.4Co0.45 in the aqueous solutions of alkali metal hydroxides of diverse composition and concentration was tested. Correlation was observed between the alloy corrosion intensity in various hydroxide solutions, and its electrochemical capacity in these electrolytes. Mm(OH)3, CoO(OH), and nickel metal aggregates were detected among the products of selective oxidation of the alloy. High intensity corrosion of the alloy was observed in RbOH and CsOH solutions leading to formation of ternary oxides at the surface of the alloy. Presence of rubidium and cesium ions in the electrolyte were found to create an additional driving force for lanthanides (La and Ce) to leave the lattice of the alloy, thus, enhancing its corrosion. Corrosion, together with mechanical degradation, were found to be the main reasons of deactivation of LaMm-Ni4.1Al0.3Mn0.4Co0.45 alloy upon elongated electrochemical treatment.

Modeling of Corrosion Rate and Resistivity of Steel Reinforcement of Calcium Aluminate Cement Mortar

Calcium aluminate cement (CAC) is a binder whose hydrated compounds change over time from cubic phases to hexagonal phases, producing an increase of porosity in reinforced concretes. Thereby, chloride ions, among other steel corrosion promoters, can enter the concrete more easily leading to an increase of the reinforcement corrosion process. When such a transformation of phases is completed, a characteristic value regarding both corrosion intensity (Icorr) and resistivity (related to the ohmic drop of the cementitious material) is reached, which depends mainly on the mix proportions of the material and the curing procedure. This paper presents the characteristic corrosion intensity values of steel embedded in mortars made of CAC after five years of exposure to either a 0.5 mol/l or 1.5 mol/l NaCl solution in order to be applied to estimate the service life of reinforced concrete made of calcium aluminate cement (CAC) which is used in real construction structures. Ohmic drop measurements are also presented to support the values obtained. The aim of this paper is to model the corrosion rate and resistivity of the steel reinforcement of calcium aluminate cement mortar with regard to environmental factors (temperature and chloride content) and mortar quality (water/cement ratio).