Protective Pigments Research Articles

The Electrochemical Impedance Study of Corrosion Protection of Bronze by Waterborne Organic Coating/Phosphonic Acid Protective System

The use of organic coatings is the most common method for corrosion protection of metals. However, the majority of the organic coatings are solvent borne. Nowadays, there is a great interest for their replacement by more environmentally friendly waterborne coatings. Unfortunately, their application poses practical problems due to their poor surface wetting, lower level of protection as well as the corrosion of metal substrate. This problem is especially pronounced in protection of bronze cultural heritage due to the requirement that coating does not change the visual appearance of the substrate, which limits the use of protective pigments in the coating. In addition, coating must successfully protect, not only the bronze substrate, but the adhering patina as well.This work examines the use of waterborne acrylic coating in combination with pretreatment by a long-chain phosphonic acid as a solution for protection of bare and patinated bronze surface. Electrochemical impedance spectroscopy studies are conducted on bare and chemically patinated bronze protected by waterborne coating or by combined protection system phosphonic acid/waterborne coating. In this way it is possible to evaluate the influence of phosphonic acid pretreatment on overall coating protection. Studies are conducted under various aging conditions, including the continuous immersion into artificial acid rainwater, climatic chamber with NO2 introduction and outdoor exposure. The obtained results show that phosphonic acid pretreatment improves the overall corrosion protection level of acrylic coating as the phosphonic acid acts as a corrosion inhibitor. However, some differences in the EIS spectra evolution in time are observed when comparing the results from different aging conditions. This differences are related to the coating swelling and underlying patina transformation under studied corrosion conditions. Acknowledgment: This work was fully supported funded by the Croatian Science Foundation under the project IP-2019-04-5030

Microscopic Raman study of fungal pigment using the genetically amenable rock inhabitant Knufia petricola as a model organism

Fungal pigments such as melanin and carotenoids are distinctive markers of animal and plant pathogenic fungi as well as their environmental relatives. These complex pigments play important roles in pathogenicity and stress tolerance while also being useful as biomarkers. Accordingly, it is important to be able to identify in situ the pigments in black fungi, a group of clinical and environmental importance. In this study, wild-type and genetically modified strains of Knufia petricola A95 and wild fungal cells attached to ancient rock were investigated for their spectroscopic and microscopic Raman features and morphological appearance. Knockout mutants of melanin synthesis genes pks1 (polyketide synthase), sdh1 (scytalone dehydratase), and both pks1 and the carotenoid synthesis gene phd1 (phytoene desaturase) were studied We applied two different Raman microscopes using two lasers, with 633 nm and 488 nm wavelengths. We analyzed and compared Raman spectra between the measured reference substances and the mutant and wild-type strains. In the wild strain WT:A95, the peaks close to melanin peals were found at 1353 cm−1 and 1611 cm−1. There are no characteristic melanin peaks at 1580–1600 cm−1 and around 1350 cm−1 at the spectrum of the Δpks1/Δphd1 mutant and the Δsdh1 mutant. The Δpks1 mutant spectrum has the peaks at the beta-carotene v2 C-C in-plane stretch at 1155 cm−1 and v3 C-CH3 deformation at 1005 cm−1. The peaks of carotenoids and melanin were found in all mutants and the wild strain, except the Δpks1/Δphd1 mutant. Raman spectra allow for discrimination between the various pigments. Hence, interactions between natural fungal melanin, as well as other protective pigments, and complex environmental matrices can be characterized on a range of spatial and temporal scales.

In English

Nanocomposites containing components with semiconductor, ferroelectric, and ferromagnetic properties have attracted considerable attention of specialists due to the range of possible applications, including catalysis and electrocatalysis, electrode materials for solar and fuel cells, capacitors, electrical and biosensors, anti-corrosion coatings and much more. In recent years, both fundamental and applied interest in this direction of research is due to the possibility of creating a new type of controlled microwave devices and tools. The aim of the work is to develop methods for the synthesis of nanostructured NiCo composites based on BaTiO3 and TiO2, as well as to find the differences and regularities of their physicochemical properties. Two series of samples with different content of NiCo nanoparticles based on titanium oxide (TiO2) and barium titanate (BaTiO3) were obtained. NiCo particles were obtained by the method of chemical precipitation of nickel and cobalt carbonates in equal parts from a hydrazine hydrate solution at the temperature of 350 K. The results of X-ray phase analysis indicate the chemical purity of the obtained samples. The values of ε′, ε″ at a frequency of 9 GHz for the NiCo/BaTiO3 system are twice as high compared to NiCo/TiO2 for the corresponding values of the NiCo content, which is due to the higher values of ε′, ε″ of the initial barium titanate. Electrical conductivity of NiCo/BaTiO3 system changes by six orders of magnitude, which indicates the formation of a continuous percolation cluster of metal particles on the surface of dielectric BaTiO3 particles. The composites are heat-resistant up to 630K, as shown by the method of thermogravimetry and pronounced magnetic properties. The program for calculating frequency dependences of reflection and absorption coefficients in a complex form has been developed. EMF absorption for composites from the radiation frequency and the position of the minima of these characteristics, which agree satisfactorily with the experiment. The obtained composites can be promising components for obtaining composite systems and paints for protection against electromagnetic radiation.

Investigation of the Physiological Effects of Plant Conditioners in Field Experiments of Winter Wheat

Our study aimed at to test the effects of two different plant conditioners on some morphological parameters, yield and grain quality of winter wheat (Babona) in a field experiment with medium plots, and to investigate some physiological parameters closely related to yield quantity and quality at the beginning of ear emergence by in vivo field measurements. At the beginning of ear emergence we determined the relative chlorophyll content of leaves (SPAD value), moreover leaf reflectance was measured with a portable spectroradiometer to produce spectral vegetation indices that can be used to evaluate the effects of treatments on chlorophyll, carotenoid, anthocyanin and water content of leaves, and to infer photochemical efficiency and stress sensitivity. The results were strongly influenced by the unfavourable rainfall distribution during the growing season. Precipitation deficit in spring significantly reduced the development of the crop stand (yield was below the national and county levels), and its effect was also observable in quality parameters (low raw protein and gluten content), but the positive effect of treatment 1 was detectable: higher yield and quality, higher plant height and ear length compared to the control. At the beginning of ear emergence, some spectral vegetation indices indicated the positive effect of treatment 1 despite the drought: chlorophyll content and photochemical activity of leaves were higher, and higher stress sensitivity and protective pigment concentration in the control.

Fire Resistance of a Building Element with Intumescent Fire Protection: Standard Assessment and Express Analysis

Introduction. The paper considers the problem of fire resistance assessment of building structures with intumescent fire protection. For the results reliability, a fire test should be carried out only when the intumescent coating at the facility is ready, which will make it possible to detect hidden factors of violation of its quality and prevent collapse in case of a possible fire. The work objective is to test the express analysis of intumescent coatings in comparison with standard methods for fire resistance assessment.Materials and Methods. The elements of building structures covered with fire-resistant intumescent paint Defender M Solvent with different diluent content were studied. The fire resistance of the coatings was determined by two methods. The first one is an express analysis. The following indicators were recorded:– general appearance of the coked cellular material (CCM);– swelling coefficient;– CCM compressive and shear-tear strength of the boundary layer.The second one is a standard approach according to the requirements of ISO 834-75 (GOST 30247.0-94). The indicators were:– time to reach the critical temperature;– critical deflection during heating.Results. In addition to the above indicators, testing also took into account the amount of diluent. The CCM swelling coefficient, CCM compression force, tensile strength and density were considered. The revealed patterns are systematized in a table. The obtained indicators were compared with the technical requirements for the material. The period during which the steel substrate of the sample reaches a critical temperature is recorded. It is established that with an increase in this time, the coefficient of swelling of the protective layer (CCM) and its shear-tear strength increases. At the same time, the values of compressive strength and CCM density decrease. When the intumescent paint is diluted beyond the norm, the fire protection parameters deteriorate and the fire resistance limit R45 is not reached. The research results are visualized in the form of diagrams. They confirm that the express analysis makes it possible to reasonably judge the suitability or unsuitability of the paint for fire protection, if the required fire resistance limit is R45.Discussion and Conclusions. In comparison with the results of the application of standard techniques, the effectiveness of the express analysis technique and the correctness of the results of the assessment of intumescent fire protection were confirmed. In construction conditions, an express CCM analysis will be sufficient to determine the quality of an intumescent fire retardant coating.

Comparative biodeterioration at air interfaces of adipate-based polyester polyurethane coatings by fungal microcolonies of Aureobasidium sp. W12

Understanding conditions that enable environmentally common microbes to aggressively deteriorate polymer materials are important for predicting and controlling the environmental fates of these materials. For protective paints and coatings in terrestrial environments, processes at air interfaces are among important factors to understand. Here, we track fungal biodeterioration at air/solid polymer interfaces under nutrient limitation and high humidity, using polymer compositions common in commercial polyester polyurethanes. A fungal isolate, Aureobasidium sp. W12, was collected from an aircraft and identified as a polyester degrader through screening assays. Two polyadipate-based materials were then used for W12 coating deterioration analysis: a commercial polyester polyurethane, Irogran® PS455–203, and a model polyester urethane, PEA-HM. Single and micro-aggregated cell clusters distributed within ∼1.5 mm diameter regions were prepared on the polymer surfaces and incubated with no supplemental nutrients at >95% relative humidity for up to 13 days. Coating deterioration was semi-quantitatively monitored through ester carbonyl loss by transmission FTIR spectroscopy and both materials were rapidly deteriorated, although at different rates. With ∼0.5 monolayer cell surface coverage, PEA-HM showed about 6 × greater molar ester deterioration versus Irogran® over the first 24 h. By 13 days, the polyester fractions of Irogran coatings were deteriorated to an average depth of about 0.1 µm, while PEA-HM coatings about 1 µm thick were completely deteriorated in 5 days within and beyond cell covered regions. Localized analysis of non-uniform PEA-HM deterioration showed that quantities on the order of 10 individual Aureobasidium yeast cells could locally deteriorate through 1–2 µm of PEA-HM coating within 12 days (with deterioration rates up to about 2 × 10−6 µmol ester / (cell × day)). These results correlate conditions and polymer properties that promote high deterioration potentials of Aureobasidium W12 microcolonies at air / coating interfaces.

Studi Eksperimen Laju Pertumbuhan Biofouling Pada Pelat Baja Dan Aluminium Dengan Lapisan Pelindung Lilin Dan Minyak Di Pantai Boom Banyuwangi

Indonesia is a maritime country with a tropical climate and has various biofouling species. The existence of fouling in a marine structure has a large impact on losses if it is not addressed immediately. Antifouling is needed to overcome the presence of fouling. Various development efforts to inhibit, prevent and eliminate biofouling continue to be made. Generally, the method used by the public is by using commercial antifoulant protective paints with heavy metal main components such as TBT (tri-n-butyl tin). However, currently various studies have proven that TBT compounds are not only toxic to biofouling biota but also harmful to other marine organisms. Further research is needed to find antifouling alternatives that do not contain toxic compounds and are more environmentally friendly. This study was designed to determine the growth rate of marine growth in steel and aluminum plate materials at Boom Banyuwangi Beach by using a protective coating in the form of oil and wax. From the results of the research designed, it can be analyzed the efficiency of using protective layers of oil and wax with steel and aluminum materials on the growth rate of marine growth according to the conditions of the waters of Boom Banyuwangi Beach. The use of oil protectors on steel and aluminum test specimens resulted in more efficient results in inhibiting the growth rate of biofouling than the use of wax protectors

Micro combustion calorimeter for development of fire protective paints

Micro combustion calorimeter for development of fire protective paints

Analytical Investigations of XIX-XX Century Paints: The Study of Two Vehicles from the Museum for Communications of Frankfurt.

Over the centuries, humans have developed different systems to protect surfaces from the influence of environmental factors. Protective paints are the most used ones. They have undergone considerable development over the years, especially at the turn of the 19th and 20th centuries. Indeed, between the two centuries, new binders and pigments have been introduced in the constituent materials of paints. The years in which these compounds have been introduced and spread in the paint market allow them to be defined as markers for the dating of paints and painted artifacts. The present work is focused on the study of the paints of two vehicles of the Frankfurt Museum of Communication, i.e., a carriage and a cart, that was designed for the German Postal and Telecommunications Service roughly between 1880 and 1920. The characterization of the paints was performed through in situ non-invasive techniques, i.e., portable optical microscopy and multispectral imaging, and laboratory non-destructive techniques, i.e., FT-IR ATR spectroscopy and SEM-EDS. The analytical investigation and the comparison with the data reported in the literature allowed us to determine the historicity of the paints, which are all dated before the 1950s.

Synthesis of Blue Gahnite (ZnAl2O4:Co, Nd): A Cost-Effective Method for Producing Solar-Reflective Pigments for Cool Coatings.

Developing strategies for the green synthesis of novel materials, such as pigments for protection from solar radiation, is a fundamental research subject in material science to mitigate the heat island effect. Within this perspective, the current study reports on the synthesis of blue pigments of ZnAl2O4:M (M = Co2+ and Co2+/Nd3+) using recycled metallic aluminum (discarded can seal) with reflective properties of Near-infrared radiation. The pigments were characterized by XRD, SEM, XPS, UV-Vis, NIR diffuse reflectance spectroscopy, and CIE-1976 L*a*b* color measurements. The wettability of the coatings containing the synthesized pigments was also evaluated. The structural characterization showed that the pigments present the Gahnite crystalline phase. Colorimetric measurements obtained by the CIEL*a*b* method show values correlated to blue pigments attributed to Co2+ ions in tetrahedral sites. The pigments exhibit high near-infrared solar reflectance (with R% ≥ 60%), with an enhancement of nearly 20% for the pigment-containing neodymium when applied in white paint, indicating that the prepared compounds have the potential to be energy-saving color pigments for coatings.

Scytonin in gypsum endolithic colonisation: First Raman spectroscopic detection of a new spectral biosignature for terrestrial astrobiological analogues and for exobiological mission database extension

Microbial colonisations of gypsum from Eastern Poland (Badenian, Middle Miocene age) were investigated by Raman microspectrometry with a rarely used excitation 445 nm excitation. Zones of microbial colonisation in selenitic gypsum endolithic outcrops comprise algae and cyanobacteria, which commonly contain the photosynthetic and protective pigments carotenoids, scytonemin and gloeocapsin. Diagnostic bands differing from those of scytonemin have been identified in black colonies in gypsum outcrops at Chotel Czierwony (Poland). Raman spectral signatures of scytonin are reported here for the first time in two endolithic specimens identified by the band wavenumbers predicted from DFT calculations. The strong or medium strong intensity Raman bands observed at 1603, 1585, 1559, 1435, and 1424 cm−1. Other weaker bands were located at 1676 (sh), 1660 (sh), 1649, 1399, 1362, 1342, 1320, 1294, 1272, 1259, and 1052 cm−1. The first observation of the Raman spectrum of scytonin in the cyanobacterial colonisation of gypsum facilitates the inclusion of this new biomolecular signature in the library of unique Raman spectra of biological pigments invaluable for detection of traces of life in frame of the planetary missions.

Exploiting HOPNO-dicopper center interaction to development of inhibitors for human tyrosinase

In human, Tyrosinase enzyme (TyH) is involved in the key steps of protective pigments biosynthesis (in skin, eyes and hair). The use of molecules targeting its binuclear copper active site represents a relevant strategy to regulate TyH activities. In this work, we targeted 2-Hydroxypyridine-N-oxide analogs (HOPNO, an established chelating group for the tyrosinase dicopper active site) with the aim to combine effects induced by combination with a reference inhibitor (kojic acid) or natural substrate (tyrosine). The HOPNO–MeOH (3) and the racemic amino acid HOPNO-AA compounds (11) were tested on purified tyrosinases from different sources (fungal, bacterial and human) for comparison purposes. Both compounds have more potent inhibitory activities than the parent HOPNO moiety and display strictly competitive inhibition constant, in particular with human tyrosinase. Furthermore, 11 appears to be the most active on the B16–F1 mammal melanoma cells. The investigations were completed by stereospecificity analysis. Racemic mixture of the fully protected amino acid 10 was separated by chiral HPLC into the corresponding enantiomers. Assignment of the absolute configuration of the deprotected compounds was completed, based on X-ray crystallography. The inhibition activities on melanin production were tested on lysates and whole human melanoma MNT-1 cells. Results showed significant enhancement of the inhibitory effects for the (S) enantiomer compared to the (R) enantiomer. Computational studies led to an explanation of this difference of activity based for both enantiomers on the respective position of the amino acid group versus the HOPNO plane.

An insight into the variation of the antioxidative and antibacterial activity of extracts from populations of the subalpine and montane lichen Cetraria islandica

Lichens are supra-organismal symbiotic systems found in most environments. Environmental factors, such as temperature, altitude, precipitation, UV irradiation, or pathogens, significantly influence the physiology of lichens, and thus their secondary metabolism. The thalli of the same lichen species from different environments exhibit variation in the production of secondary metabolites and protective pigments. We selected two populations of the lichen Cetraria islandica from habitats differing in altitude, temperature, and precipitation. Then we compared their antioxidative and antibacterial activity. The lichen thalli were divided into two parts: the upper parts were exposed to light and the lower parts hidden from extensive radiation. The results show that the thalli from harsh alpine environments have higher 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical scavenging activity suggesting better tolerance to oxidative stress. On the other hand, the individuals from milder montane environments generally produce more secondary metabolites, leading to increased antibacterial activity of the extracts. The extracts of C. islandica containing fumarprotocetraric and paraconic acids exhibit inhibitory effects against gram-positive bacteria (e.g. Staphylococcus aureus) and some lower activity against gram-negative bacteria (e.g. Escherichia coli).

Using of acoustic resonance for detection and identification of hidden defects in polymer layered composites

A method of non-destructive testing is proposed, which combines the acoustic load of the object of inspection and interferometric control of its surface displacements, formed as a result of an acoustic wave resonance in a hidden defect. The method is aimed at solving the problem of detection and identification of subsurface defects formed in structural elements made of polymer layered composite materials or contain protective paint coatings. At the same time, the defect is considered as an acoustic resonator filled with a medium in which only a longitudinal acoustic wave propagates. Usually such media are air or water. The novelty of the method is that it allows us not only to detect a hidden defect and establish its location, but also to determi¬ne its dimensions. The scheme of the experimental installation is given and the method is described. The research of the detection and identification of subsurface defects that most often occur in practice was conducted with the help of the model of the experimental installation. In products made of polymer layered composites, such defects are unbounded areas between layers during construction, internal damages such as cracks and areas of crumpling during its operation. The results of the experiments proved the effectiveness of the proposed method. The described method is also suitable for detection and identification of blistering of protective paint coatings, provided that they are filled with liquids or gases in which transverse acoustic waves do not propagate.

Novel multifunctional acrylic paint from sugarcane bagasse: Photoluminescence, photochromism, hydrophobicity and anticorrosion

Novel graphene oxide-based waterborne acrylic emulsion paints were prepared for multifunctional smart coatings with long-persistent photoluminescence, anticorrosion, hydrophobic and photochromic properties. Environmentally friendly graphene oxide nanosheets were successfully prepared through ferrocene-catalyzed oxidation of sugarcane bagasse agricultural waste under muffled conditions. An acrylic polymer was combined with graphene oxide and lanthanide-doped strontium aluminate nanoparticles to create innovative photoluminescent paint for use in safety marking. The graphene oxide nanosheets were used in the acrylic paint as crosslinker, as well as drying and anticorrosive agent. Different concentrations of lanthanide-doped strontium aluminate nanoparticles were tested. As a result of its unique characteristics, graphene oxide has become an appealing reinforcing agent that can be used in protective paints. The produced acrylic/graphene oxide/lanthanide-activated aluminate coatings were applied onto tinplates. The dispersion of phosphor was improved in the paint matrix by using the phosphor in the nanoscale form (4–8 nm). The morphological properties of the graphene oxide nanosheets were studied. Different research analysis methods were used to examine the morphologies of the applied paints. Photoluminescence spectra and CIE Lab properties were used to analyze the applied paints transparency and colorimetric properties. The photoluminescent transparent paints showed green emission at 518 nm when excited at 365 nm. The prepared paints demonstrated high photostability and durability. Scratching resistance, hydrophobicity, and corrosion resistance were all examined.

Quality evaluation of organic protective paints using terahertz pulse imaging technology based on wavelet packet energy method

It is particularly important to make quality evaluation for paint spraying process. This work presented an efficient method based on wavelet packet energy for terahertz non-destructive evaluation of organic protective paint. The wavelet packet energy analysis algorithm was summarized. Various coating structures were experimentally investigated using terahertz pulsed imaging system and the relative wavelet energy and the Shannon entropy of the detected signal were calculated as wavelet energy indexes. The proposed algorithm was performed on the evaluation of coating unevenness and the identification of hidden corrosion defect. The results demonstrated that the wavelet energy indexes are sensitive to coating structure change when compared to the terahertz peak-finding method, and it allowed more accurate estimate of micro corrosion defect. Therefore, the proposed approach based on wavelet packet energy could be recommended for quick quality evaluation of organic coating with terahertz non-destructive technology.

IN-VITRO MELANOGENESIS, CYTOTOXICITY AND ANTIOXIDANT ACTIVITIES OF Peltophorum pterocarpum LEAF EXTRACTS

Melanin is a protective pigment against cellular damage and skin cancer. Peltophorum pterocarpum has been used for centuries to treat skin diseases like eczema and psoriasis. However, whether P. pterocarpum leaf extract can affect melanin synthesis with the advantage of antioxidant defense against ultraviolet (UV) radiation remains to be investigated. We aimed to examine the melanogenesis, cytotoxicity, and antioxidant activities of P. pterocarpum leaf extracts. A two-dimensional (2D) cell culture model was employed to demonstrate the effect of P. pterocarpum extracts on melanin synthesis. The cell viability of B16-F1 melanoma cells was measured by Neutral Red Uptake (NRU) assay. Antioxidant activity was accessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2’,7’-dichlorodihydrofluorescein diacetate (DCFH-DA) assays. The ethanol extract of P. pterocarpum dose-dependently increased the melanin content and displayed cytotoxicity to B16-F1 melanoma cells at the highest concentration. In contrast, the equal amounts of the aqueous extract significantly inhibited melanin synthesis and did not show any cytotoxic effects on B16-F1 melanoma cells. The P. pterocarpum ethanol extract had a significantly higher total phenolic and flavonoid content than the aqueous extract and was more effective at scavenging DPPH free radicals and intracellular ROS induced by UVB, with IC50 of 519.24 ± 122.57 vs 1798.45 ± 143.09 µg/mL and 878.00 ± 23.50 vs 1379.00 ± 21.81 µg/mL, respectively. These findings suggest that the pro-melanogenic and anti-melanogenic activities of P. pterocarpum extract with antioxidant capacity against UVB-induced cellular damage are affected by the total phenolic and flavonoid contents.

Characterization and Evaluation of Water-Based Ecological Paint for Protection of Wood Materials Coated Using Dipping Technique

The aim of this study was to characterize and evaluate the performance of two wood species, pine (Pinus sylvestris L.) and spruce (Picea abies Karst.) used for wooden furniture in outdoor coated with a water based ecological paint and subjected to artificial weathering. Another task of this research was to investigate the potential of the application of paint using dipping method in alternative to traditional brush or spraying coating application methods, since, if wood samples are grouped in stacks, the processing time can be reduced, compared to samples painted singularly. From the analysis of the dipping parameters, such as time and paint concentrations, more practical and specific knowledge was obtained regarding this painting method.From the characterization of the painted samples and from the measurements of color changes during artificial weathering it was observed that coated wood surfaces have similar optical properties also in case of different dipping times, although the type of wood could affect the performance of final product during artificial weathering test as in case of spruce wood samples, specifically those prepared with the shortest dipping time: for these samples a lower resistance to weathering and higher color changes were observed.

The Influence of Distinct Seasons on the Succession and Diversity of Bacteria on the Anticorrosive Coatings Surfaces in a Marine Environment

Epoxy resin has been frequently used as a coating paint for anticorrosion protection because of its excellent chemical properties. However, the long-term succession of bacteria colonizing coatings surfaces in the different seasons of the year remains uncharacterized. In this work, amplicon-based 16s rDNA sequencing was used to characterize the tempol change of bacterial communities growing on the epoxy resin surfaces. The results showed that bacterial diversity indices on spring and autumn immersion samples were higher than that of the samples immersed on summer and winter samples. Proteobacteria was found to be the dominant bacteria of all different seasons and accounted for 57.9% of the total sequence. Gammaproteobacteria and Alphaproteobacteria were the dominant classes in all of the samples, whereas the most abundance bacteria at the genus level had the significant differences with a change of season. Firmicutes also displayed a distinct temporal change pattern in that it was the second abundance in the summer and autumn samples, but had a marked decrease in the other season samples. These results demonstrated that bacterial community composition underwent obvious changes over the distinct seasons of a year. This study will be helpful for the seasonal change of bacterial diversity and development of corrosion-resistant paints.

The location of adsorbed water in pigmented epoxy-amine coatings

Pigmentation can exacerbate problematic water uptake into protective paints, leading to detrimental effects such delamination, swelling and plasticization. Potential underlying mechanisms include poor adhesion between the pigment and binder, the formation of hygroscopic interphase regions close to the pigment particles, and internal stress. Here, we demonstrate the use of nanoscale chemical mapping using AFM-IR and nanothermal analysis to investigate the contribution of these mechanisms directly for model coatings based on diglycidyl ether of bisphenol-A (DGEBA) cross-linked with triethylenetetramine (TETA). Whilst moisture uptake increases in the presence of a microscale silica matting agent, no chemical interphase could be detected close to the wax-coated particles. Instead, nanothermal analysis reveals attenuated thermal expansion of the polymeric binder and raised Tg values, supporting favourable polymer-pigment interaction and an increase in internal stress in the polymeric network. This is confirmed by mapping water distributions directly using AFM-IR, where no accumulation at the intact pigment-polymer interface/interphase is detected. Finally, further evidence is provided by bulk thermal analysis, where increased plasticization and desorption enthalpies demonstrate that water sorption into the bulk polymer binder increases as a function of added pigment volume concentrations.