Benjamín Valdez Salas

Effect of H2S on corrosion in polluted waters: a review

Abstract The present article provides an overview of the effect of hydrogen sulphide (H2S) on corrosion in polluted waters, including sea, river, brackish, geothermal and sewage waters. H2S is a weak, reducing acid which originates from sulphide minerals by natural acidification and/or from sulphur – bearing, decaying organic matter by bacterial action. Human and industrial activities increase the generation of corrosive gases, dissolved in water: CO2, H2S and NH3. Carbon steel, stainless steel, aluminium alloys and copper base alloys are corroded by H2S, producing metallic, non-stable sulphide films. The H2S content in various waters, the electrode potential pH (Pourbaix) diagrams for Fe and Cu in H2S containing systems, and the electrochemical and corrosion performance of steel in oxygen depleted, H2S polluted waters, which indicate active corrosion behaviour, are presented and discussed.

Interesting Behavior of Pachycormus discolor Leaves Ethanol Extract as a Corrosion Inhibitor of Carbon Steel in 1 M HCl: A Preliminary Study

The purpose of this paper is to evaluate the inhibitive action of an ethanol extract from the leaves of Pachycormus discolor (EEPD) on the corrosion of carbon steel in 1 M HCl at different temperatures; gravimetric method and electrochemical tests were conducted. Potentiodynamic polarization was used at room temperature and resistance polarization at different temperatures. Thermodynamic adsorption parameters are shown in order to demonstrate the spontaneous adsorption. The inhibition of EEPD was performed via adsorption of the extract species on the carbon steel surface. The ethanol extract obeys Langmuir adsorption isotherm. Potentiodynamic polarization results indicate that the ethanol extract acts as a mixed type inhibitor. The results revealed that the inhibition efficiency (IE) of EEPD increases (when the concentration is increased). Phytochemical and FTIR analyses are also presented in this work. It was found that the IE increases with the temperature in a 2.0% v/v solution which showed 94.52% IE at 25∘C and 97.89% at 75∘C.

Copper Corrosion by Atmospheric Pollutants in the Electronics Industry

Hydrogen sulphide (H2S) is considered one of the most corrosive atmospheric pollutants. It is a weak, diprotic, reducing acid, readily soluble in water and dispersed into the air by winds when emitted from natural, industrial, and anthropogenic sources. It is a pollutant with a high level of toxicity impairing human health and the environment quality. It attacks copper forming thin films of metallic sulphides or dendrite whiskers, which are cathodic to the metal substrate, enhancing corrosion. H2S is actively involved in microbially influenced corrosion (MIC) which develops in water, involving sulphur based bacteria, in oxidizing and reducing chemical reactions. H2S is found in concentrated geothermal brines, in the atmosphere of geothermal fields, and in municipal sewage systems. Other active atmospheric pollutants include SOX, NOX, and CO. This investigation reports on the effects of H2S on copper in microelectronic components of equipment and devices, with the formation of nonconductive films that lead to electrical failures.

Micro and Nano Corrosion in Steel Cans Used in the Seafood Industry

The use of metal containers for food preservation comes from the early nineteenth century, has been important in the food industry. This type of packaging was developed to improve food preservation, which were stored in glass jars, manufactured for the French army at the time of Napoleon Bonaparte (XVIII century), but were very fragile and difficult to handle in battlefields, so it was decided the produce metal containers (Brody et al, 2008). Peter Durand invented the metallic cans in1810 to improve the packaging of food. In 1903 the English company Cob Preserving, made studies to develop coatings and prevent internal and external corrosion of the cans and maintain the nutritional properties of food (Brody, 2001). Currently, the cans are made from steel sheets treated with electrolytic processes for depositing tin. In addition, a variety of plastic coatings used to protect steel from corrosion and produce the adequate brightness for printing legends on the outside of the metallic cans (Doyle, 2006). This type of metal containers does not affect the taste and smell of the product; the insulator between the food and the steel, is non-toxic and avoid the deterioration of the food. The differences between metal and glass containers, as well as the negative effects that cause damage to the environment and human health are presented in Table 1. The wide use of steel packaging in the food industry, from their initial experimental process, has been very supportive to keep food in good conditions, with advantages over other materials such as glass, ceramics, iron and tin. The mechanical and physicochemical properties of steel help in its use for quick and easy manufacturing process (Brown, 2003). At present, exist a wide variety of foods conserved in steel cans, but in harsh environments, they corrode. Aluminum is used due to its better resistance to corrosion, but is more expensive. With metal packaging, the food reaches to the most remote places of the planet, and its stays for longer times without losing its nutritional properties, established and regulated for health standards by the Mexican Official Standards (NOM). The difference between using metal cans to glass (Table 1) indicate greater advantages for steel cans (Finkenzeller, 2003). In coastal areas, where some food companies operate, using steel cans, three types of deterioration are detected: atmospheric corrosion, filiform corrosion and microbiological corrosion. Even with the implementation of techniques and methods of

Corrosion in the Food Industry and Its Control

From ancient times human beings have survived on a diet consisting on a relatively few species of plants and animals, domesticated and then cultivated and grown. Three cereals, wheat, rice and corn, supply the need of human energy, protein and vitamins requirements for the network of metabolic processes to maintain normal body function and temperature. In a prehistoric era, indigenous peoples all over the world were moving in inhospitable grounds obtaining their daily sustenance by hunting and gathering fruits, seeds and roots. Actually, the three largest markets worldwide, according to their production extent, the number of consumers and their economic and social significance are the food, energy and water markets. Furthermore, their increasing scarcity and soaring prices lead to a global critical situation. The demand for increased food supply is related both, to population increase and personal and family income. Consequently, the food market is the largest one, including all the inhabitants of this planet, about seven billion, since everyone eats! The organized food production and supply starts with the agricultural revolution, developed and implemented in the fertile valleys of the rivers Tigris-Euphrates in Mesopotamia and the Nile in ancient Egypt. Afterwards the food industry expanded, avoided widespread famine and ensured that sufficient food is supplied for all people to stay healthy. Current food research had been largely stimulated by rapidly growing world demand but technological advances in food processing, equipment and production plants have also contributed. A most significant aspect in the search of new nutritional food is the requirement for adequate protein in regions where meat and fish are not available. Additionally, advances in the food industry (FI) such as preservation, packaging and storage facilitate food delivery and minimized health hazards. Space flight conditions have stimulated the creation of space food which meets highly demanding standards for conservation and to be ready for easy digestion e.g. solid dehydrated food easily converted into liquid or paste food. Techniques for preserving food from natural deterioration following harvest or slaughter dated to prehistoric times applying drying, salting, fermentation of milk and fruits and pickling of vegetables. Modern techniques include canning, freezing, dehydration, cooking under vacuum and addition of chemicals. The principal causes of food spoilage are growth

Characterization of steel surface under cathodic protection in seawater

Purpose – The purpose of this paper is to characterize the surface of steel under cathodic protection while submerged in seawater, to understand the mechanism that controls the operation of the protection system.Design/methodology/approach – Steel rods were immersed in seawater and NaCl solution with applied cathodic protection. The experimental methodology included monitoring of corrosion potential (Ecorr), galvanic current (Igalv) protection potential (Eprotection) and the depolarization potential of steel during the time of exposure. In addition, the chemical composition of the steel surface was assessed using a Scanning Electron Microscope (SEM).Findings – In this research it was determined that the effectiveness of the CP system was mainly attributable to the formation of an iron oxide film on the steel surface.Research limitations/implications – It is necessary to carry out analysis of the chemical composition of deposits formed on the steel surface, perhaps using X‐ray diffraction (XRD), to verify ...

The Importance of Teaching Science and Technology in Early Education Levels in an Emerging Economy

In the context of technological dissemination sessions aimed at prospective students at the Polytechnic University of Baja California in the city of Mexicali, Baja California, the importance of engineering and its role in scientific and technological progress was stressed, as well as its role in scientific and technological progress as drivers of economic development in the region. A group of 2,154 students from 20 different institutions of public high school education answered a survey designed as an evaluation tool for a career path or technology area of interest. The survey results show that students have a low preference for engineering careers. Moreover, these results were augmented with an additional study on the high attrition of students in engineering schools in the city of Mexicali, Baja California, also conducted by the authors. It raises the importance of teaching science in the early education levels, which aims to prepare scientists and technologists needed for the development of research and innovation as a foundation for economic prosperity and welfare of an emerging economy such as Mexico.

Synthesis of Carbon Nanofibers with Maghemite via a Modified Sol-Gel Technique

Carbon nanohybrid material (CNF/γ-Fe2O3) was obtained via a modified sol-gel technique consisting of two steps: functionalization of carbon nanofibers (CNF) in H2SO4/HNO3 followed by synthesis using Fe(NO3)39H2O. As a result, the iron content of the CNF/γ-Fe2O3 was increased by more than twice from about 40% to about 87% mass percent, compared to the pristine CNF and oxidized CNF specimens, as proved by energy dispersive X-ray fluorescence. Scanning electron microscopy images exhibited “cumulus“ on the CNF/γ-Fe2O3 specimen surface, which showed the highest iron mass percentage, proved by energy dispersive X-ray spectroscopy. Transmission electron microscopy images confirmed attachment of γ-Fe2O3 cumulus to the inner and outer surfaces of the CNF walls after synthesis. The characteristic peaks of Fe 2p3/2 and Fe 2p1/2 appeared in the XPS spectra obtained on CNF/γ-Fe2O3. In addition, X-ray diffraction (XRD) results indicated formation of γ-Fe2O3 during the synthesis process. The Raman spectrum of the CNF/γ-Fe2O3 sample displays peaks with positions close to characteristic peaks of highly crystalline and monodisperse maghemite nanocrystallites. The synthesis of CNF/γ-Fe2O3 leads to an increase in the hydrophilicity of CNF and magnetic properties at room temperature.

La motivación de las mujeres por las carreras de ingeniería y tecnología

Resumen En los ultimos tiempos, las mujeres han incursionado con mayor frecuencia en el campo de la ingenieria, una de las carreras con mayor auge a nivel internacional. Sin embargo, la matricula de las mujeres en Mexico ha tenido un creci- miento lento: solo corresponde al sexo femenino alrededor de 30% de la poblacion total de estudiantes que cursan algun programa relacionado con ingenieria. Con el fin de dilucidar la motivacion de la eleccion de esta carrera entre las mujeres, se aplico una encuesta a las alumnas inscritas a la carrera de Ingenieria Aeroespacial de la Facultad de Ingenieria de la Universidad Autonoma de Baja California, en el semestre 2014-1. Asimismo, se indaga el modelo de desempeno futuro de las estudiantes mujeres inscritas en carreras de ingenieria, en el municipio de Mexicali. Los hallazgos demuestran que no existe un modelo femenino a seguir, por lo que se propone la inclusion de un modelo Ciencia, Tecnologia, Ingenieria y Matematicas ( STEM , por sus siglas en ingles), en la Facultad de Ingenieria, para incrementar la inclusion, preferencia y matricula de mujeres en esta area del conocimiento.

Poster Paper: Image Analysis for Automatic Characterization of Nanomaterials

Nowadays, the development of new technology depends strongly on nanomaterials study, which is carried out usually by microscopy techniques allowing the images acquisition of materials for their posterior characterization. When this feature extraction is performed through a human observer it can become slow, laborious and subjective, a situation that has generated great interest in image analysis because it has the potential to overcome this problematic. This paper proposes a system based on image analysis for automatic characterization of nanomaterials. The system consists of four stages: preprocessing, segmentation, feature extraction and validation. Results of applying these stages on images acquired with different microscopy techniques are shown. Finally, some challenges and opportunities in this area are discussed.