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.

The requirement for sustainable and environmentally friendly materials has led to the exploration of lignin as a potential candidate for protective coatings in various industrial applications. Recent researches demonstrate the feasibility of lignin-based coatings for enhancing wear and corrosion resistance. The lignin improved the coating's barrier properties and prevented corrosive electrolytes from contacting the metal. The lignin additives also functionalised wear resistance coating. This review points out the improvements in using lignin extraction to produce high-quality materials suitable for corrosion and wear resistance coating purposes. However, the application of lignin in coatings faces significant challenges, primarily due to its heterogeneous and complex nature, which complicates the attainment of uniform and reliable coating qualities. Moreover, it emphasises the need for further studies on lignin to harness lignin's potential. Future research needs include the development of standardised methods for lignin characterisation and modification, the exploration of novel lignin-based composites and the evaluation of lignin coatings in real-world applications. This review probes into the burgeoning field of lignin-based coatings, evaluating their potential for wear and corrosion resistance, and discusses the current state of research, challenges and future directions in this promising area.

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.

Microgels have been widely used for stabilizing emulsions due to their softness and stimulus responsiveness. Although ultrastable emulsions have been prepared by microgel nanoparticles, the role of electrostatic interactions on emulsion stability is still a controversial topic and further investigation of the effect of microgel deformability is required. In the present study, neutral poly(N-vinylcaprolactam) (PVCL) and charged poly(N-vinylcaprolactam)-co-methacrylic acid (P(VCL-co-MAA)) microgels were synthesized and further used as emulsifiers to stabilizing emulsion. The P(VCL-co-MAA) microgel has a swelling ratio larger than that of the PVCL microgel in water. The nanomechanical properties of the microgels in water were characterized by atomic force microscopy with using the tip of different radii. The result reveals that the P(VCL-co-MAA) microgel is more deformable than the PVCL counterpart. Stability tests of the emulsions showed that below the volume phase transition temperature (VPTT) of the microgels, both microgel types can stabilize the emulsions under various conditions. Unexpectedly, most of the emulsions still remain stable above the VPTT. Further increasing the temperature to 60 °C, P(VCL-co-MAA) microgel emulsions remained stable at a pH value above the pK_a of MAA while the emulsion was unstable below the pK_a. However, phase separation occurs in PVCL microgel-stabilized emulsions at 60 °C. These results demonstrate that electrostatic repulsion and deformability of the microgels can enhance the emulsion stability, providing insights into the rational design and preparation of ultrastable Pickering emulsions.

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.