Influence of robust drain openings and insulation stand-offs on corrosion under insulation behavior of carbon steel

CUI (corrosion under insulation) is among the key concerns for the integrity of process equipment and pipelines. Various measures to detect and fix the damages from CUI pose significant maintenance expenditures in hydrocarbons processing facilities. The key reason behind CUI is the limitation of thermal insulations to absorb the moisture and soak the underneath metal from wicking action. Other than CUI, trapped moisture in the soaked thermal insulations causes heat loss from process systems, thereby posing the risk of additional damage mechanisms and increased operating expenditures. This study addresses the impact of robust drain openings and insulation stand-offs on the CUI rate of carbon steel under four different testing conditions namely isothermal wet, isothermal wet-dry, cyclic wet, and cyclic wet-dry, respectively. Corroded specimens were further characterized using surface topography and scanning electron microscope. The impacts of temperature and moisture cycling on the corrosion attributes were also characterized using the linear polarization resistance method followed by an investigation of corrosion modes via optical microscopy. Insulation stand-offs in conjunction with robust drain opening resulted in the lowest corrosion rate. With insulation stand-offs and drain openings, the cyclic temperature conditions caused higher metal loss than that in isothermal conditions.

Experimental Substantiation of Parameters of Protective Electrochemical Polarization of Gas Pipelines in Frozen Soils

An urgent issue in the operation of Bovanenkovo-Ukhta gas pipelines in conditions of frozen and seasonally thawing soils is the refinement of parameters of anticorrosive electrochemical protection of gas pipelines. The article discusses the process of determining corrosion activity of water samples that differ in the degree of mineralization during sequential cooling to freezing using the polarization resistance method using an FT-360-40 liquid cryostat and IPC-pro potentiostat with a set of working and auxiliary electrodes.

Anti-tarnish silver alloys in system Ag-Cu-Zn-Si with the addition of aluminum

This paper presents investigations of aluminum addition influence on the corrosion characteristics of the sterling silver Ag-Cu-Zn-Si alloys. The procedure for obtaining Ag-Cu-Zn-Al-Si alloys in small ranges of predefined composition was also presented. Open circuit potential measurements, linear polarization resistance method and potentiodynamic polarization tests were employed to determine corrosion characteristics of the alloys. The materials were tested in a 0.01M sodium sulfide solution. It was shown that the addition of aluminum improves sulfidization resistance and corrosion characteristics. Best results are achieved for the alloy with the following composition 92.5% Ag, 1.9% Cu, 3.7% Zn, 1.6% Al and 0.3% Si.

Composition and

Principles of three component Iron-Cobalt-Tungsten alloys electrodeposition from complex Fe (III) based citrate electrolytes are discussed. It is shown, that deposition of ternary alloys proceeds through competitive reduction of cobalt and tungsten with iron. With increasing ligand concentration coatings are enriched with a refractory component; however, increasing current density favors a reverse trend. The effect of both current density and pulse on/off time on the quality, content of alloying metals and surface topography of electrolytic coatings were determined. The application of pulsed electrolysis provides increasing tungsten content up to 13 at.%, at current efficiency of 70–75%. Globular relief of Fe-Co-W coatings is caused by refractory metals incorporation, and crystalline and amorphous parts of structure are visualized by X-ray spectroscopy, including inter-metallic phases Co7W6, Fe7W6 along with α-Fe and Fe3C. The crystallite size of the amorphous part is near 7–8 nm. Corrosion resistance of the coatings is 1.3–2.0 orders of magnitude higher than the substrate parameters as follows from data of polarization resistance method and electrode impedance spectroscopy.

Design of anti-tarnish sterling silver Ag-Cu-Zn alloy and investigation of silicon addition influence on mechanical and corrosion characteristics

This paper presents investigations of the influence of silicon addition on the mechanical and corrosion characteristics of the sterling silver Ag-Cu-Zn alloys. The procedure for obtaining Ag-Cu-Zn-Si alloys in small ranges of composition was also presented. Vickers hardness tests and three electrochemical tests were performed on the samples in this study. Open circuit potential measurements, linear polarization resistance method, and potentiodynamic polarization tests were employed to determine corrosion characteristics of the alloys. The materials were tested in 0.9% NaCl solution, artificial sweat, 0.1 and 0.01 M sodium sulfide solutions. It was shown that addition of silicone increases hardness and generally improves sulfidation resistance and corrosion characteristics in near-neutral chloride solutions of the Ag-Cu-Zn alloys.

Corrosion of reinforced steel in the environment of blast furnace slag and steelmaking slag

This article focuses on corrosion of the steel reinforcement in the concrete where the blast or demetalized steelmaking slag as one of the components for fabrication was used. The slag from iron and steel production from U.S. Steel Kosice was used in the experiment. Steel reinforcement type S 235 (STN 11 375) were made by cold drawing. Chemical composition of slag in form of powder and slag leachates was analysed using X-ray fl uorescence spectrometry. Corrosion tests were carried out by measuring the polarization curves based on potentiodynamic polarization of steel samples exposed in leachate and also by polarization resistance method directly on the steel embedded in concrete and exposed in atmospheric precipitation. The results revealed differences in the corrosion rate, depending on chemical composition of the slag, which is closely related to its metallic and sulphur content.

Inhibitive Effect of Fatty Amide and Secondary Species on the Corrosion of Carbon Steel

The effect of hydrazine, N2H4 in the presence of fatty amide as corrosion inhibitor on corrosion of carbon steel in 3.5 wt% NaCl solution was studied by linear polarization resistance method (LPRM) at room temperature and static condition. The specimens’ surface analysis was done using atomic force microscope (AFM). The inhibition efficiency improved to more than 80% when 500, 100 and 2000 ppm of hydrazine were added to the inhibited solution containing 20 ppm fatty amide. The results obtained show that the inhibition effect is increased with increase of hydrazine concentration in inhibited solution. It indicates that hydrazine retards the reduction of oxygen in the corrosion process by reacting with dissolved oxygen in the solution and thus, further it reduces the corrosion rate of carbon steel.