The present research investigates the influence of surface roughness imparted by cold surface finishing processes on the localized corrosion resistance of stainless steel. Five different alloys were studied: ferritic AISI 430, martensitic AISI 430F, austenitic AISI 303, AISI 304L, and AISI 316L. It was demonstrated that the grinding process, executed on previously cold drawn bars, leads to an improvement in corrosion resistance according to the results obtained with electrochemical tests, namely, potentiostatic and potentiodynamic tests in chloride-rich environments, the salt spray test, and long-term exposure in urban and marine atmospheres. This allowed us to establish a trend among the different alloys regarding the resistance to pitting corrosion, which was assessed according to pitting potentials, critical chloride contents, and pitting initiation time. All the tests confirmed that surface finishing, as well as alloy chemical composition, is an important factor in controlling the corrosion resistance of stainless steel.

Inhibitors for the prevention of corrosion in reinforced concrete are chemical substances able to reduce carbon steel reinforcements corrosion without altering the overall properties of concrete. Today, many commercially available substances have a negative impact on human safety during either the inhibitor synthesis, their handling or application in field. Green corrosion inhibitors are nontoxic, biodegradable and environmentally biocompatible substances. They are generally made of extracts from natural plants or waste, which are abundantly available in several countries. The majority of green inhibitor molecules usually contain multiple bonds, aromatic rings, polar functional groups and electronegative atoms as P, N, S or O; the latter are able to coordinate with metal cations to form protective layers on the metallic surface of the reinforcements, so as to inhibit the development (initiation and/or propagation) of the corrosion process. In this review, the most recent achievements on the study and investigation of green corrosion inhibitors for concrete structures are presented and discussed. Inhibitors are classified based on their nature and inhibition mechanism. The inhibition effectiveness of the substances is compared with the well-established effective nitrite-based inhibitor, distinguishing between accelerated and long-term tests. Based on the available data, a summary of corrosion inhibitors efficiency is reported.

This research study describes recent advances in understanding the effects of the addition of organic acids, such as acetic, lactic, citric and phytic acids, on the process of plasma electrolytic oxidation (PEO) on Ti using an alkaline bath. As the plasma developed over the workpiece is central to determine the particular morphological and structural features of the growing oxide, the focus is then on the inter-relationships between the electrolyte and the resultant plasma regime established. In situ optical emission spectroscopy (OES) allowed us to verify a marked plasma suppression when adding low-molecular-weight anions such as acetates, resulting in short-lived and well-distributed discharges. Conversely, when more bulky anions, such as lactates, citrates and phytates, were considered, a less efficient shielding of the electrode caused the build-up of long-lasting and destructive sparks responsible for the formation of thicker coatings, even >30 µm, at the expense of a higher roughness and loss of compactness. Corrosion resistance was tested electrochemically, according to electrochemical impedance spectroscopy (EIS), and weight losses evidenced the coatings produced in the solution containing acetates to be more suitable for service in H₂SO₄.

This research describes the influence of two types of particles, namely rutile and anatase microparticles (average d < 5 µm), on the morphology, structure, and anticorrosive properties of PEO coatings on titanium produced in an alkaline solution based on NaOH and sodium metasilicates. The paper reports the experimental results relating to the study of the influence of the electrical regime and working frequency of the anodizing treatment on the interaction between the particles, the substrate, and the oxide to determine the optimal conditions that favour the incorporation of the particles and the production of a thick oxide. PEO coatings are characterized by using a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, and X-ray diffraction (XRD) testing. The electrochemical behaviour is evaluated by free corrosion potential monitoring and electrochemical impedance spectroscopy analysis (EIS) performed in a sulphuric acid solution. The particles are successfully incorporated into the coating under any electrical condition and at any frequency. However, only treatments carried out at 1000 Hz allow the production of coatings that combine a large thickness (up to 50 µm) and improved anticorrosion behaviour. In contrast, oxide layers produced at 20 Hz and in DC show a quite damaged structure, affecting their anticorrosion behaviour and resulting in lower corrosion potential and impedance values.