Advances in Corrosion and Protection of Materials (Second Edition)

1. Introduction and Scope

As modern civilization, through its extensive use of metallic materials, has given rise to progressively more aggressive environmental conditions, corrosion resistance has become a prominent issue. The foundations of this challenging scenario are based on a solid understanding of corrosion mechanisms and protective methods. The current knowledge in this field is rapidly growing from intense research activity.

In its second edition, this Special Issue will provide a forum for the corrosion research community as a source for new developments and innovations in this field.

2. Contributions

This volume comprises 11 research papers that cover different topics related to corrosion mechanisms and protection methods of metallic materials. In the first paper, Jiménez-Come et al. (contribution 1) developed a model based on artificial neural networks (ANNs) to predict the corrosion susceptibility of different stainless-steel grades in simulated biogas environments. The precision and accuracy values reached 96.8% and 96.6%, depending on the input data. The breakdown potential of the stainless steel was considered a relevant parameter to attain high-precision modeling, along with its composition, indicated by the pitting resistance equivalent number (PREN).

Gardic et al. (contribution 2) studied the effect of 1-Phenyl-5-mercaptotetrazole (PMT) as a corrosion inhibitor for the Cu24Zn5Al alloy in sodium sulfate solution. Depending on the PMT concentration, the formation of a protective film on the surface of the copper alloy was attained, decreasing its corrosion rate.

Buier et al. (contribution 3) prepared cresol-red loaded chitosan coatings on zinc substrates as a protective method in sodium sulfate solutions with different concentrations. The anionic cresol-red interacted with positively charged chitosan, acting as a corrosion inhibitor for zinc. The corrosion resistance was monitored for up to 55 days by electrochemical impedance spectroscopy, increasing with respect to the initial immersion time due to the interaction between the cresol-red dye and the chitosan layer.

Rodic et al. (contribution 4) combined two protection strategies to protect commercially pure aluminum substrates from corrosion. They prepared one hybrid Si-O-Zr sol–gel coating and, thereafter, a 100 nm thick Al₂O₃ layer produced by thermal atomic layer deposition (ALD), which was used to seal the coating pores. This strategy was effective at improving the corrosion resistance of the aluminum substrate.

Gaona-Tiburcio et al. (contribution 5) tested the effectiveness of anodization treatment to protect Ti CP2, Ti-6Al-2Sn-4Zr-2Mo, Ti-6Al-4V, and Ti Beta-C from corrosion in sodium chloride and sulfuric acid solutions. The corrosion protection ability of the anodized layer was dependent on its thickness and, ultimately, on the alloy’s composition. The anodized films were less uniform for alloys with higher concentrations of β-stabilizing elements.

Anodizing is also an important corrosion protection method for magnesium and its alloys. Braga et al. (contribution 6) explored this strategy to improve the corrosion resistance of the ZK60A Mg alloy (Mg-Zn-Zr), using graphene oxide as an additive in an anodizing bath. The corrosion resistance was dependent on the graphene oxide concentration added to the solution, which was maximized at 1 g/L due to a better distribution within the anodized film.

Jiang et al. (contribution 7) studied the influence of different surface defects (point and line defects) on the corrosion resistance of carbon steel–titanium composite plates in a simulated marine solution. These composites are typically used for structural applications, such as bridges, pipelines, and offshore platforms. The corrosion mechanism was affected by the relative thickness between the carbon steel and titanium plates.

Graphene oxide coatings can be deposited on magnesium alloys to improve their corrosion resistance. This approach was used by Silva et al. (contribution 8), who produced graphene oxide coatings on the AZ91D Mg alloy using a simple immersion-based process and an intermediate silane layer to promote better adhesion to the substrate. Corrosion resistance was remarkably affected by the coating morphology, which, in turn, depended on the concentration of graphene oxide in the coating-forming solution.

The galvanic corrosion between Cu and Au in print circuit boards (PCBs) takes place during the etching process, which is part of PCB manufacturing. Shin and Oh (contribution 9) evaluated the corrosion inhibition efficiency of sodium dodecyl sulfate (SDS) and polyethylene glycol (PEG) in the galvanic corrosion of Cu/Au couples. PEG showed a better inhibition efficiency than SDS. In another publication (contribution 10), cetyltrimethylammonium bromide (CTAB) and betaine were evaluated as corrosion inhibitors for the same type of galvanic couples. The best inhibition efficiency was obtained for betaine (99.1%), which adsorbed copper and gold surfaces, while CTAB preferentially adsorbed on copper surfaces and exhibited an inhibition efficiency of 92.3%.

Orabi et al. (contribution 11) evaluated the A. orientalis L. extract (AO) as a green corrosion inhibitor for aluminum in acidic solutions. Using electrochemical tests and DFT simulation studies, the inhibition mechanism of the AO extract was identified. It exhibited a mixed-type inhibition mechanism (anodic and cathodic) and reached approximately 68% inhibition efficiency.