Atomic Force Infrared Microscopy (AFM-IR), also known as Photothermal Induced Resonance (PTIR), is a scanning probe spectroscopic technique that enables chemical characterization with submicron spatial resolution. This capability is especially valuable in corrosion science, where the chemical composition and phase distribution of metal alloy microstructures play a critical role in corrosion initiation, progression, and the formation of reaction products—key factors that determine long-term material performance. In this study, PTIR and infrared microspectroscopy were employed to investigate the influence of microstructure on corrosion product formation on ZnAlMg-coated steel exposed to SO₂-containing humid air. The analysis revealed that MgSO₄·7H₂O and MgSO₃·nH₂O predominantly form in eutectic regions. High-resolution PTIR measurements further showed preferential corrosion of microscopic MgZn₂ phases within the lamellar binary eutectic. This localized corrosion is attributed to micro-galvanic coupling, where MgZn₂ acts as the anodic site and Zn-rich phases serve as cathodic regions. These findings underscore the significant role of microstructural phase distribution in corrosion behavior and demonstrate the utility of PTIR for spatially resolved chemical analysis for complex metallic alloys.

The corrosion performance of line-produced prepainted galvanized steel products was investigated upon the distance to the seashore in temperate environment over 8-year exposure. The rate of underpaint corrosion from cut-edge was estimated and depended on the agressiveness of the site and the angle of exposure. The delamination at cut-edge in sheltered conditions can be predicted from corrosivity category on steel and zinc and may be connected to the distance to the seashore. The extent of blistering decreased when extending the distance to the seashore particularly in rinsed situations underlining the importance of seawater aerosols but also wetness and condensation for blistering formation and propagation

The corrosion of metals in soils is a major problem for asset managers within the infrastructure and energy sectors. Usually, the soil corrosivity class is defined using standards and field tests. In the context of solar park structures' durability, the present study was conducted for 2 years, in which the corrosion behavior of carbon steel, pure zinc, and hot-dip galvanized steel was investigated through exposure to a variety of global unsaturated soil environments. Test sites included sandy and clay soils with varying pH levels and electrical resistivities. Corrosion was evaluated through visual inspection, mass-loss measurements, and characterization of corrosion products using Raman and Fourier transform infrared spectroscopy. Results highlight the critical influence of soil moisture, oxygen availability, resistivity, and sulfates on corrosion rates. Notably, the Fe/Zn corrosion rate ratio highlighted the material-specific sensitivity to soil chemistry. Severe localized penetration and zinc coating consumption were observed in poorly-drained saline sandy soil, challenging the predictive accuracy of the current DIN 50929 standard

The Erichsen cupping test is widely used to evaluate formability and adhesion of coil-coated materials, as it produces strains comparable to industrial forming. In the present work, a hot-dip galvanized steel with a polyester/melamine primer and topcoat was selected. Mechanical deformations were applied using a spherical indenter at penetration depths of 1-6 mm. Coating thickness along the deformation profile was measured on cross-sections by optical microscope. The effective contact area of the coating with the electrolyte in the electrochemical cell was determined by 3D scanning. Electrochemical impedance spectroscopy in a 0.5 M NaCl solution over 72 h was used to assess water uptake and anticorrosion performance, following methodologies developed in previous studies. The influence of coating thickness and effective contact area on the EIS-calculated water uptake was examined. A deformation threshold (≥5 mm) was identified, above which blister initiation was strongly accelerated. Failure mechanisms such as cracks in the Zn layer and loss of coating adhesion leading to blistering were characterized using electrochemical measurements and post-mortem SEM-EDS observations. The approach provides relevant dielectric and electrochemical markers for understanding how mechanical deformation influences water uptake and failure in coil-coatings

This paper is dedicated to long-term atmospheric corrosion behaviour of magnesium alloys. Five different magnesium alloys, namely, AZ31, AM60, AZ61, AZ80, and AZ91, were exposed for 4 years under harsh conditions at the marine corrosion site of Brest (France). From the results, the corrosion performance increased in the following order: AZ31 < AM60 < AZ91 < AZ61 < AZ80. The corrosion was highly localised during the first year of exposure, but more general corrosion prevailed after long-term exposure. All materials followed a power law with rather similar kinetics of corrosion. The observed difference in the corrosion performance of the alloys was explained by the amount of secondary phases as well as that of the Al-content in the α-Mg phase

In the present study, ex situ Fourier transform infrared (FTIR) chemical imaging and in situ electrochemical impedance spectroscopy (EIS) were combined to investigate the ageing process of a polyester/melamine coil-coated steel. The samples were first subjected to a QUV accelerated weathering test for 250 h up to 2000 h, followed by immersion in a 0.5 M NaCl solution to assess water uptake and polymer matrix plasticization. FTIR analyses revealed chemical degradation, including chain scission and the formation of polar groups, between 500 h and 2000 h of QUV exposure. Degradation effects were observed throughout the whole topcoat, with more significant degradation occurring near the surface. EIS measurements indicated greater water uptake with increasing QUV exposure, highlighting two regions of water sorption: an initial rapid Fickian diffusion region and a slower non-Fickian region. The time constant (τ) analysis, which was extracted from the EIS data and related to the dielectric manifestation of the glass transition, confirmed polymer matrix plasticization due to water uptake. Despite UV-induced degradation, the polymer maintained effective protective properties, as evidenced by the high low-frequency impedance unaffected by UV exposure or immersion duration (1 week). This methodology successfully identified ageing markers, providing a framework for studying UV degradation mechanisms, water uptake, and polymer mobility in anticorrosion coatings. 

The initial formation of corrosion products in pure humid air on magnesium alloys AZ91 and AZ31 was studied using infrared reflection absorption spectroscopy (IRRAS), infrared spectroscopic imaging, and SEM-EDS. The kinetics of corrosion product formation were monitored in situ with IRRAS during exposure to humid air (95% relative humidity) under two different CO2 concentrations: low (≤1 ppm) and ambient (400 ppm). For low CO2 concentrations, the primary corrosion product detected on both alloys was magnesium hydroxide (Mg(OH)2). In contrast, under ambient CO2 conditions (400 ppm), magnesium hydroxy carbonate was the dominant product. After 16 h of exposure, the amount of magnesium converted into corrosion products was approximately 8–10 times higher under low-CO2 conditions compared to ambient levels. The smaller formation of corrosion products but increased magnesium carbonate formation on AZ91D is attributed to its higher aluminium content compared to AZ31. Corrosion attack and product formation were largely localised to the centre of the α-phase in AZ91D, with the β-phase likely serving as sites for cathodic reactions.

This work aims to assess the susceptibility to stress corrosion cracking (SCC) of additively manufactured (AM) 316L stainless steel by laser-based power bed fusion (PBF-LB) and compare its performance with conventional manufacturing (CM), i.e. wrought 316L. Also, the influence of different surface conditions was analyzed. Potentiodynamic polarization tests in artificial seawater were used to obtain electrochemical properties, such as pitting breakdown potential (E<inf>bd</inf>) and corrosion potential (E<inf>corr</inf>). Stress corrosion cracking susceptibility was measured using U-Bend specimens, using concentrated artificial seawater droplets, simulating non-rinsing atmospheric conditions in marine environments. The specimens were exposed to temperatures between 40 and 60 °C and relative humidity of 40 %. For the AM specimens, two surface conditions were tested: as built and after machining process. A higher threshold temperature was observed for 316L-AM, indicating a better SCC resistance, than the 316L-CM, hence L-PBF can be used as an alternative manufacturing route for replacing 316L-CM as better properties were achieved. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and superficial residual stress measurements were used to aid the discussion of the SCC results. These tests revealed better passive layer properties in the AM material and formation of strain-induced martensite in the CM after bending, leading to higher residual stress

During the 2000s, the concept of cathodic protection (CP) shielding was first raised in open literature and remains debated between coatings professionals. The mechanism of CP shielding, and its understanding continue to be studied for different coatings with different approaches and using various techniques. From the CP shielding factors to the assessment methods, the published literature merits a deep analysis to capture the established knowledge and identify the research gaps to further tackle the issue for reliable coated buried structures. A holistic approach to this topic seems necessary where coatings ageing, cathodic protection, electrochemistry, and transport processes should be considered. In the first part of the present review, the recent works related to the understanding of CP shielding, coatings properties were considered before discussing the mechanisms involved underneath coatings. Transport phenomena and their relationship with cathodic protection performance in the presence of chemical and microbiological processes are discussed in the second part. Finally, CP shielding assessment methods and modeling works are presented and discussed from different perspectives. 

New environmental regulations have led to major changes in aluminum corrosion protection by prohibiting, for example, Cr(VI). Thus, the assessment of the corrosion behavior of Cr-free systems under atmospheric conditions is a major topic of interest for the aerospace industry. One major difficulty in this task is the lack of robust and reliable accelerated corrosion test(s) in this field. The aim of the present study is to compare the results of various accelerated corrosion standards (ASTM B117, ISO 4623-2, VCS 1027,149) to results obtained after 5 years of exposure at a marine atmospheric site in Brest, France. Additional accelerated corrosion tests were designed by varying several parameters in the VCS 1027, 149, such as the salt concentration, the time of wetness, and the relative humidity. The different modes of failure obtained in accelerated corrosion tests on the painted samples were then compared to field exposures in a marine atmospheric site. The first results obtained showed that the developed tests are more representative of service conditions than standard tests. © 2024 by the authors.