Almost all organic coatings used for corrosion protection contain various types of pigmentation, both for the sake of aesthetics and performance. By focusing on spatially resolved vibrational spectroscopy and electron microscopy, we demonstrate that the type of pigmentation has a fundamental effect on both localized and global degradation processes across the investigated coatings. Samples with white TiO2 pigments display low macroscale chemical degradation across the surface but do experience a significant change in topography. SEM-EDS imaging shows that µm-scale craters are formed around the TiO2 pigments. Nanoscale spatially resolved IR spectroscopy (AFM-IR) suggests that this local erosion is not triggered by reactions seen in coatings with other types of pigments. However, FTIR-ATR chemical imaging of coating cross sections confirmed that the TiO2 pigments also protects material beneath the surface, resulting in very shallow chemical degradation effects as compared to the other systems. Darker coatings, containing carbon black, experience moderate to high chemical degradation across the surface, and additionally the degradation propagates deep into the coatings. Overall, this paper highlights that single criteria should not be used when comparing the degradation of different coatings.

Corrosion and wear pose significant challenges to equipment operating in harsh environments. Thus, protective coatings are needed. Anti-corrosion and anti-wear coatings are traditionally fossil-based and often contain environmentally harmful additives. Achieving anti-corrosion and anti-wear coatings based on environmentally benign and sustainable materials is important and a significant challenge. This work focused on the development of organosolv lignin-based polyurethane (OS_lignin-PU) coatings. The coatings were synthesised and evaluated for corrosion protection using electrochemical impedance spectroscopy (EIS) and for wear properties using nanoindentation and nano scratch measurements. EIS revealed that the optimal lignin content for corrosion protection purposes in the OS_lignin-PU coatings was 15 wt%. Moreover, addition of 15 wt% lignin to the OS_lignin-PU coatings also enhanced their wear resistance, as evidenced by reduced thickness loss during tribometer tests. The nano scratch measurements revealed that OS_lignin-PU coatings containing 15 wt% lignin exhibited the lowest scratch depth and friction coefficient. It is found that the developed lignin-containing coating exhibits remarkable corrosion and wear resistance, making it a promising sustainable material in various applications for pursuing sustainable development.

Strongly attractive forces act between superhydrophobic surfaces across water due to the formation of a bridging gas capillary. Upon separation, the attraction can range up to tens of micrometers as the gas capillary grows, while gas molecules accumulate in the capillary. We argue that most of these molecules come from the pre-existing gaseous layer found at and within the superhydrophobic coating. In this study, we investigate how the capillary size and the resulting capillary forces are affected by the thickness of the gaseous layer. To this end, we prepared superhydrophobic coatings with different thicknesses by utilizing different numbers of coating cycles of a liquid flame spraying technique. Laser scanning confocal microscopy confirmed an increase in gas layer thickness with an increasing number of coating cycles. Force measurements between such coatings and a hydrophobic colloidal probe revealed attractive forces caused by bridging gas capillaries, and both the capillary size and the range of attraction increased with increasing thickness of the pre-existing gas layer. Hence, our data suggest that the amount of available gas at and in the superhydrophobic coating determines the force range and capillary growth.

Corrosion causes significant challenges in industrial settings, leading to economic losses and safety concerns. Previously, we developed a lignin-polydimethylsiloxane (lignin-PDMS) coating that exhibited high corrosion resistance. However, the adhesion of the developed lignin-PDMS coating to carbon steel was limited, affecting its overall performance. To address this, we incorporated dopamine (DOPA), known for its strong adhesive properties, as a pre-treatment before applying the coating. It was found that the adhesion and corrosion resistance of lignin-PDMS coated steel could be improved by adjusting the pH value of the DOPA solution. The steel treated with pH 4.5 DOPA solution showed two times higher adhesion strength to the coating than non-treated steel. After the DOPA treatment, the coating can maintain high barrier property for at least 3 months in 1 M NaCl solution, which is even better than commercial gelcoat, demonstrating super corrosion protection. Quartz Crystal Microbalance with Dissipation (QCM-D) and X-ray Photoelectron Spectroscopy (XPS) analyses confirmed the DOPA deposition on the steel surface. Our findings show that the DOPA-lignin-PDMS system is an environmentally friendly and efficient solution for enhancing the durability of steels in corrosive environments.

Corrosion and wear remain significant challenges for materials, causing substantial economic losses and safety risks. Anti-corrosion and anti-wear coatings provide an effective solution. However, traditional coatings are often fossil-based and contain heavy metals, posing environmental concerns. The drive for eco-friendly coatings has led to the exploration of green materials. This study combined lignin, an abundant organic material, and polydimethylsiloxane (PDMS), a known hydrophobic material, to address the challenges. Organosolv lignin was functionalised with (3-Aminopropyl)triethoxysilane (APTES), then chemically grafted on PDMS for the final coating synthesis. The optimised coating achieved through an eco-friendly process, exhibiting enhanced hydrophobicity and barrier properties, showing excellent long-term corrosion resistance in NaCl solution. The optimal coating formulation contained 15 wt% lignin and 40 wt% PDMS, demonstrating a high corrosion resistance (measured impedance of 1010 Ω·cm2), which remains effective even after 3 weeks of immersion in 1 M NaCl solution. This coating also showed good wear resistance, with a low friction coefficient evident from nano scratch tests.

In this study, molecular dynamics simulations were employed to analyze interactions between phospholipid membranes and human serum albumin (HSA) in the presence of mono- and divalent cations. Two types of membranes, composed of dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidylethanolamine (DPPE), were utilized. The results revealed that both systems exhibited high stability. The DPPE complexes displayed a greater affinity for albumin compared to DPPC. The high stability of the complexes was attributed to a high number of ionic contacts and hydrogen bonds. The presence of mono- and divalent metal cations significantly influenced the membrane’s capacity to bind proteins. However, these effects varied depending on the phospholipid composition of the bilayer. The studies confirmed the relatively low ability of DPPC to bind potassium ions, as previously observed by others. Consequently, the DPPC/HSA/K+ complex was found to be the least stable among the systems studied. While DPPC interactions were limited to HSA domains I and II, DPPE was able to interact with all domains of the protein. Both lipid bilayers exhibited substantial structural changes and characteristic curvature induced by interactions with HSA, which confirms the formation of relatively strong interactions capable of influencing the arrangement of the phospholipids.

Local heterogeneities can have significant effects on the performance of anti-corrosion coatings. Even small features can act as initiation points for damage and result in corrosion of the substrate material. Analysis methods with high spatial resolution and the ability to collect information relevant to crosslinking and degradation behavior of these coatings are therefore highly relevant. In this work, we demonstrate the utility of nanomechanical AFM measurements and nano-FTIR in investigating the nanoscale mechanical and chemical properties of two polyester coil coating clearcoats before and after weathering. On the nanoscale, weathering led to a stiffer and less deformable coating with less variation in the nanomechanical properties. Chemical degradation was quantified using changes in band ratios in the IR-spectra. Macro and nano-scale measurements showed similar trends with the latter measurements showing larger heterogeneity. Our results demonstrate the usefulness of the described analysis techniques and will pave the way for future studies of local properties in other coating systems and formulations.

Current methods for monitoring coating corrosion are limited by their inability to provide real-time data and dependence on external power sources. This study presents a novel in-situ corrosion monitoring system using a solid-liquid triboelectric nanogenerator (TENG) that converts mechanical energy into electrical signals for selfpowered sensing. TENG signals and electrochemical impedance spectra were measured on a dopaminemodified lignin-polydimethylsiloxane coating on steel in 1 M NaCl solution under no corrosion, indentation, pitting, and broken conditions, respectively. We extract time-frequency features from the TENG signals to predict the coating's corrosion condition by applying a customised convolutional neural network (CNN). By extracting time-frequency features from the TENG signals and applying a custom CNN, a prediction accuracy of 99 % for corrosion classification was achieved. Furthermore, the CNN regression model predicted coating impedance values with a high coefficient of determination (R2 = 0.98), demonstrating its effectiveness in tracking corrosion progression. The developed TENG also facilitates defect localisation via a matrix electrode beneath the coating. Our approach introduces a promising real-time technology for in-situ corrosion monitoring.

A fundamental understanding of the interactions between mineral surfaces and amphiphilic surface modification agents is needed for better control over the production and uses of mineral fillers. Here, we controlled the carboxylic acid layer formation conditions on calcite surfaces with high precision via vapor deposition. The properties of the resulting carboxylic acid layers were analyzed using surface-sensitive techniques, such as atomic force microscopy (AFM), contact angle measurements, angle resolved X-ray photoelectron spectroscopy (XPS), and vibrational sum-frequency spectroscopy. A low wettability was achieved with long hydrocarbon chain carboxylic acids such as stearic acid. The stearic acid layer formed by vapor deposition is initially patchy, but with increasing vapor exposure time, the patches grow and condense into a homogeneous layer with a thickness close to that expected for a monolayer as evaluated by AFM and XPS. The build-up process of the layer occurs more rapidly at higher temperatures due to the higher vapor pressure. The stability of the deposited fatty acid layer in the presence of a water droplet increases with the chain length and packing density in the adsorbed layer. Vibrational sum frequency spectroscopy data demonstrate that the stearic acid monolayers on calcite have their alkyl chains in an all-trans conformation and are anisotropically distributed on the plane of the surface, forming epitaxial monolayers. Vibrational spectra also show that the stearic acid molecules interact with the calcite surface through the carboxylic acid headgroup in both its protonated and deprotonated forms. The results presented provide new molecular insights into the properties of adsorbed carboxylic acid layers on calcite.

The formation of a bridging gas capillary between superhydrophobic surfaces in water gives rise to strongly attractive interactions ranging up to several micrometers on separation. However, most liquids used in materials research are oil-based or contain surfactants. Superamphiphobic surfaces repel both water and low-surface-tension liquids. To control the interactions between a superamphiphobic surface and a particle, it needs to be resolved whether and how gas capillaries form in non-polar and low-surface-tension liquids. Such insight will aid advanced functional materials development. Here, we combine laser scanning confocal imaging and colloidal probe atomic force microscopy to elucidate the interaction between a superamphiphobic surface and a hydrophobic microparticle in three liquids with different surface tensions: water (73 mN m(-1)), ethylene glycol (48 mN m(-1)) and hexadecane (27 mN m(-1)). We show that bridging gas capillaries are formed in all three liquids. Force-distance curves between the superamphiphobic surface and the particle reveal strong attractive interactions, where the range and magnitude decrease with liquid surface tension. Comparison of free energy calculations based on the capillary menisci shapes and the force measurements suggest that under our dynamic measurements the gas pressure in the capillary is slightly below ambient.