Corrosion inhibitors are commonly used to reduce the effects of corrosive processes in metallic materials. However, many compounds are toxic and expensive and have negative effects on the environment. There is growing interest in replacing petroleum inhibitors with biodegradable inhibitors, such as plant extracts. Barley agro-industrial waste (AW) is a source of compounds with great inhibitor activity, and its use is desirable for minimizing the amount of AW. The aim of this paper is to demonstrate the application of an AW extract as a corrosion inhibitor for stainless steel AISI 304 in H 2 SO 4 . The efficiency of this acid extract was evaluated by weight loss measurements, scanning electron microscopy (SEM) analysis, open circuit potential (OCP) measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization curves (PP). The proposed extract exhibited an inhibition efficiency of up to 97% and was physically adsorbed in the metallic surface. The SEM images indicated that the addition of the extract decreased metal oxidation. The electrochemical results for steel in the presence of the AW extract acted as a mixed-type inhibitor, likely changing the cathodic mechanism reaction on the uncovered surface. The AW extract can thus be used as an organic corrosion inhibitor.
The current studies aim to apply natural products as corrosion inhibitors, once the most used compounds are mostly toxic to the environment and to humans. The present paper purposes the application of an aqueous extract of agro-industrial waste (AEAW) to inhibit the corrosion of stainless steel AISI 304 in sulfuric acid. Gravimetric and electrochemical experiments were performed. The gravimetric experiments revealed that the extract acts as an inhibitor for stainless steel, showing inhibitory efficiency up to 81.6%. The electrochemical tests show that the AEAW makes the steel surface more noble. The extract acts by adsorption in the metallic surface, following a Temkin isotherm. The results indicate that the AEAW is a promising substitute of conventional organic compounds as a corrosion inhibitor to AISI 304 stainless steel in sulfuric acid.
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This work proposes the development of a niobium phosphate coating (PNb) to replace the zinc phosphating, which is very aggressive to the environment and human health. The metallic material utilized was carbon steel (SAE 1010), which was coated with sunbathing - gel containing phosphate and niobium. A traditional zinc phosphate coating was used for comparison of results. The samples were characterized by scanning electron microscopy (SEM), dispersive energy spectroscopy (DES), open circuit potential, electrochemical impedance spectroscopy and anodic polarization. The results demonstrated that the samples coated with niobium phosphate have more surface nobility and greater corrosion resistance.
Some metals prior to receiving a layer of paint should be submitted to a treatment of metal surface, since they are subjected to corrosion. This work aims the obtaining and characterization of a coating based on ceramics of cerium and / or zirconium for metal surfaces treatment. The ceramics were obtained by immersing the aluminum alloy 3003 and the carbon steel (SAE 1010) in the polymeric resin of citric acid and ethylene glycol according to the Pechini method. The characterization of the samples was performed using the following techniques: scanning electron microscopy (SEM), open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and Potentiodynamic Anodic Polarization (PAP). It was confirmed that the coatings of cerium and / or zirconium presented themselves as promise in the treatment of metal surfaces, because both showed good resistance, protecting the metal from corrosion.
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