Volume 37, Issue 2

Over the decades, corrosion has resulted in loss of lives accorded with damage costs in almost all engineering fields. Thus, it is seen as an environmental threat with catastrophic attributes, which calls for day-to-day research on its final resolution. Recent studies have proven organic green corrosion inhibitors (OGCIs) from plant extracts with biodegradable, environmentally accommodative, relatively cheap, and nonharmful features as the most perfect approach of tackling the problem. This review gives succinct discussion on the mechanisms, classifications, and active functional groups of OGCIs. Measuring ways and factors influencing their efficiency are presented. Also, various plant extracts used as OGCIs in preventing material corrosion in corrosive media coupled with their respective findings, applied characterization techniques, and future challenges are presented. The significance of values obtained from simulating presented mathematical models governing OGCI kinetics, adsorption isotherm, and adsorption thermodynamics is also included. In conclusion, recommendations that will broaden the usage of OGCIs from plant extracts for inhibiting corrosion of materials are presented for prospective researchers in the field of corrosion.

Environment quality, clean energy and worldwide water scarcity have been established today as central disciplines in modern science, engineering and technology. The innovative desalination technology of saline water (SW) contributes to alleviate these problems by producing fresh water from SW, mainly seawater and brackish water. Desalination plants (DPs) have a high level of corrosion risk as they handle and process aggressive SW under severe operating conditions, which include filtration, heat exchange, distillation, evaporation, agitation and circulation and high flow velocities, often turbulent. These SW, that is, sea, brackish and brines, cause localized corrosion such as pitting, crevice, galvanic and stress corrosion. In addition, biological fouling and mineral scaling are frequent nuisances that alter the equipment surface performance and induce corrosion. Two main technologies are used to obtain potable water and a brine for disposal: thermal evaporation and membrane separation, called reverse osmosis. The main way to minimize corrosion is the correct selection of corrosion-resistant materials for the fabrication of DP equipment, structures, installations and machinery. To protect the DP materials, industrial paints, polymeric coatings and rubber linings compatible with the DP fluids are applied. Cathodic protection with sacrificial anodic metals and/or impressed direct electrical current and corrosion inhibitors are supplied.

Corrosion affects the usefulness of metallic materials used in the construction of an effluent treatment plant (ETP). The present report investigates the corrosive and inhibitive properties of the chemicals present in the effluent of paper mill and distillery industries. Chemicals such as chloride, chlorophenols, phosphate, calcium, nitrite, and nitrate enhance corrosion, whereas the presence of sulfate, potassium, organic matter, and melanoidins (color) inhibits corrosion at an acidic pH level in distillery and paper mill effluents. A finding shows that pH level has an important role in increasing or decreasing the effect on corrosivity of effluents.

In many industries and processes, heat exchangers are of vital importance as they are used to transfer heat from one fluid to another. These fluids can be corrosive to heat exchangers, which are usually made of metallic materials. This paper illustrates that corrosion is an important problem in the operation of heat exchangers in many environments, for which no straightforward answer exists. Corrosion failures of heat exchangers are common, and corrosion often involves high maintenance or repair costs. In this review, an overview is given of what is known on corrosion in heat exchangers. The different types of corrosion encountered in heat exchangers and the susceptible places in the devices are discussed first. This is combined with an overview of failure analyses for each type of corrosion. Next, the effect of heat transfer on corrosion and the influence of corrosion on the thermohydraulic performances are discussed. Finally, the prevention and control of corrosion is tackled. Prevention goes from general design considerations and operation guidelines to the use of cathodic and anodic protection.

In recent years, a renewed interest in studying the electrochemical corrosion behavior of lead anodes during zinc electrowinning is probably due to the particularly high sulfuric acid concentrations in zinc electrolyte where lead alloy anodes have high cell voltage and high corrosion rate of lead. The high corrosion rate of lead alloy resulted in Pb contamination on zinc deposit. In zinc electrometallurgy, the electrolyte from a zinc-rich ore contains a significant amount of Mn 2+ . Mn 2+ in the zinc electrolyte results in forming an oxide film on lead anodes during electrolysis. Pb-0.7% Ag anode is generally used in the zinc industry. To improve the technical performance and decrease product cost, other anodes, such as Pb-Ca or Pb-Ag-Ca or Pb-Ag-Ti or Pb-Ag-Se alloys were tested. Till now, none of them has succeeded in the substitution of Pb-Ag anodes in the zinc electrowinning. As an alloying element, silver in small quantities is considered because of the benefits that generates on the anode during electrolysis. During zinc electrolysis, lead dissolution into the zinc electrolyte can be harmful to the quality of zinc deposit. However, the lead silver alloy anode can decrease the lead content in the zinc deposit by pre-treated methods such as blasting and preconditioning.

A series of analyses were conducted on samples of an austenitic type 304 stainless steel that exhibited a high degree of sensitization (DOS) after being subjected to a solution annealing treatment at 1050°C. The DOS was detected by electrochemical potentiokinetic tests. Examination by scanning electron microscopy of etched samples revealed the presence of δ-ferrite within the austenitic matrix, and of the segregation of chromium and nickel in either phase; images obtained by atomic force microscopy revealed localized attack at the austenite/δ-ferrite interface. It was found that the DOS and the ferrite number of the steel were reduced as the material was held at the solution temperature for longer times. Aging at 650°C showed precipitation of chromium carbides at grain boundaries and at the austenite/δ-ferrite interface; this treatment increased the DOS.