Effect of Monoethanolamine on Corrosion of A283 Carbon Steel in Propionic Acid Solution

This research studied the effect of monoethanolamine or MEA on corrosion of A283 carbon steels both in water and 5 vol.% propionic acid solution at boiling point temperature of solution. MEA concentrations ranging from 30 to 90 wt.% in water was used. The 5 vol.% propionic acid containing around 45 and 75 wt.% MEA additions (100:1 and 100:5) by volume in the test solution was studied. The carbon steel coupons were tested in a liquid phase, liquid and vapor phase and vapor phase. The weight losses of coupons were evaluated to calculate corrosion rate. A scanning electron microscope and X-ray diffraction were used to characterize the corrosion surface of coupons. The results showed that the corrosion rate order was in the liquid phase > in the liquid and vapor phase > in the vapor phase. MEA decreased the corrosion rate of A283 carbon steel both in water and 5 vol.% propionic acid solution containing around 45 and 75 wt.% MEA additions (100:1 and 100:5) by volume. MEA can be considered as corrosion inhibitor of carbon steel both in water and propionic acid solution. The formed layers of FeO(OH), Fe2O3 and Fe3O4 on the surface were detected to prevent a corrosion attack. The formed layer of Fe3C was also found and discussed. The more severe corrosion was in ferrite

Corrosion Behavior of Ni Steels in Aerated 3.5-wt.% NaCl Solution at 25ºC by Potentiodynamic Method

This work studied the corrosion behaviors of 15Ni, 23Ni, 31Ni and 40Ni steels in aerated 3.5% NaCl solutions at pH 2, 7, 10 and temperature of 25ºC. The observed microstructures of 15 and 23 wt.% Ni steels were partially martensite, but those of 31 and 40 wt.% Ni steels were fully austenite. Polarization curves of the nickel steels were measured by potentiodynamic technique. The corrosion potential (Ecorr), corrosion current density (Icorr), from which the corrosion rate (Rmpy) was calculated, pitting potential (Ep), primary passive potential (Epp) and passive current density (Ip) were evaluated form the polarization curves. The results showed that increasing nickel content increased the corrosion potentials but decreased the corrosion current density or the corrosion rate. Only pH 10, the passive characteristics of the 23Ni, 31Ni and 40Ni steels were observed. The pitting potentials and primary passive potentials of those three steels increased with nickel contents, but the passive current density decreased. Nickel improved general corrosion and pitting corrosion resistances of the tested steels in basic, neutral and acid 3.5% NaCl solutions. The effects of nickel and solution pH on general corrosion resistances of nickel steels were discussed

Microstructural and Diffusion Analysis of Au-Sn Diffusion Couple Layer Undergoing Heat Treatment at Near Eutectic Temperatures

Diffusion couples of pure gold and pure tin were created by mechanical cold rolling method. The couples were isothermally treated at temperatures slightly above and below the eutectic temperature near tin-rich region of the equilibrium phase diagram. Differences in the diffusion behaviors were observed as a function of treatment temperatures below (473 K) and above (498 K) the eutectic temperature. At the boundary, it was found that first solid state inter-diffusion was initiated which resulted in local compositional change and solid-state formation of intermetallic compounds. As the composition shifts away towards mixing, the growth of the intermetallic phases was monitored as a function of temperature and time. At temperature above the eutectic, there may be a liquid fraction as the interface isothermally melted. The kinetic involves dissolution of Au atoms into locallized tin-rich liquid. At below eutectic temperature, the formation and growth kinetic of phases follows a solid state diffusion mechanism. By investigation the exponent n values in the growth equation l = k(t/t0)n, the values were found to be in between 0.62 - 0.77 which implies that the kinetics of IMC formations experiment are controlled by both diffusion and intermetallic reaction. The bonding temperature was found to be faster and more reliable at bonding temperature slightly above the eutectic

Effective process safety management for highly hazardous chemicals

Process safety management (PSM) has been a critical consideration in the plants that handle highly hazardous chemicals (HHCs), flammable gases and liquids. This article introduces PSM standard by OSHA's 29 CFR 1910.119. Further, it highlights an effective PSM for HHCs and provides PSM practices of the industries in Thailand. Effective PSM can prevent or mitigate catastrophic releases of HHCs which can cause health problems, fires, explosions, and fatalities. It is a disciplined framework for managing the integrity of operating systems, safety critical equipment (SCE) and safe work practices. Effective implementation and audits of PSM system and the continual improvement are important. It requires the industries to execute suitable leading and lagging process safety metrics. The inclusive and integrated PSM intents, human factors, good design principles, recognized and generally accepted good engineering practices (RAGAGEPs), engineering and administrative controls, and integrity of operating and maintenance practices are substantial key roles. It is important that the PSM system should be risk-based under the ALARP concept because hazards and risks are not equal, and there are multiple risks and consequences to consider. In summary, the PSM effectiveness depends on, for example, process safety metrics, management review, audit findings and particularly workforce involvement

Comparison of the effect of non-polluted and underwater-volcano-polluted seawater on the corrosion resistance of different stainless steels

This work compares the effect of non‐polluted and underwater‐volcano‐polluted seawater on the electrochemical behavior of two different alloys, notably an austenitic stainless steel (SS) and a duplex stainless steel. Polarization measurements, potentiostatic passivation tests, electrochemical impedance spectroscopy and capacitance measurements were performed. Results show that the composition of the polluted seawater negatively affects the passivation kinetics of both AISI 316 SS and Alloy 900, decreasing the corrosion resistance of both alloys. Additionally, when both steels are compared, it can be concluded that passive films formed on Alloy 900 presented better protective properties than those on AISI 316 SS

Passivation behaviour of Alloy 31 (UNS N08031) in polluted phosphoric acid at different temperatures

The influence of temperature (20–80 °C) and chloride concentration (0.06–0.42 wt.% KCl) on the electrochemical behaviour of the UNS N08031 was studied in 40 wt.% polluted phosphoric acid solution. Passivation behaviour was investigated by using potentiostatic tests at different potentials. From the linear regions of the log i vs. log t transients, the parameter n was obtained. The results showed that the applied potential hardly affects on the passivation rate n. However, n values decreased when temperature increased. The values of n demonstrated that the passive film formed on Alloy 31 was compact and highly protective.The authors express their gratitude to the MAEC of Spain (PCI Mediterraneo C/8196/07, C/018046/08, D/023608/09 and D/030177/10), to Programa de Apoyo a la Investigacion y Desarrollo de la UPV (PAID-06-09) and to the Generalitat Valenciana (GV/2011/093) for the financial support and to Dr. Asuncion Jaime for her translation assistance.Escrivá Cerdán, C.; Blasco Tamarit, ME.; García García, DM.; García Antón, J.; Guenbour, A. (2012). Passivation behaviour of Alloy 31 (UNS N08031) in polluted phosphoric acid at different temperatures. Corrosion Science. 56:114-122. https://doi.org/10.1016/j.corsci.2011.11.014S1141225

Effect of temperature on passive film formation of UNS N08031 Cr-Ni alloy in phosphoric acid contaminated with different aggressive anions

tThe influence of temperature and the effect of aggressive anions on the electrochemical behaviour of UNSN08031 stainless steel in a contaminated phosphoric acid solution were evaluated. Stabilisation of thepassive film was studied by potentiodynamic polarisation curves, potentiostatic tests, electrochemicalimpedance spectroscopy (EIS) measurements, Mott Schottky analysis and X-ray photoelectron spec-troscopy (XPS). The stability of the passive film was found to decrease as temperature increases. The filmformed on the stainless steel surface was a n-type semiconductor and the XPS spectrum revealed thepresence of fluoride ions.Authors express their gratitude to the Ministry of Education of Spain (MHE2011-00202) for its financial support during the stay at University of Manchester, to MAEC of Spain (PCI Mediterraneo C/8196/07, C/018046/08, D/023608/09 and D/030177/10) and to the Generalitat Valenciana (GV/2011/093) for the financial support. The authors would also like to acknowledge the support of the School of Materials at the University of Manchester for providing analytical and technical support for the study.Escrivá Cerdán, C.; Blasco Tamarit, ME.; García García, DM.; García Antón, J.; Akid, R.; Walton, J. (2013). Effect of temperature on passive film formation of UNS N08031 Cr-Ni alloy in phosphoric acid contaminated with different aggressive anions. Electrochimica Acta. 111:552-561. https://doi.org/10.1016/j.electacta.2013.08.040S55256111