Paint Adhesion Research Articles

The study on performances of environment-friendly colorless chemical conversion coatings on aluminum alloy

With the increasingly high requirements on the appearance of electronic equipment and environmental protection, conventional chromate chemical conversion coatings on aluminum alloys gradually showed some shortcomings, such as the color difference in appearance and harm to human health and the environment in the process. In this paper, three kinds of environment-friendly colorless chemical conversion coatings (LANTH-613, ALTRCHR-250, YMT-631) were prepared by using 5056 and 6061 aluminum alloy samples and visually observing the appearance of the coatings. Then, the performances of the coatings, such as the morphology, corrosion resistance, electrical contact resistance, and paint adhesion, were characterized by scanning electron microscope, salt spray test, electrical contact resistance test, and cross-cut test, respectively. As a result, we proposed YMT-631 colorless chemical conversion coating could be used alone as a long-term protective coating for aluminum alloy parts that require the natural appearance of aluminum in electronic equipment, by which corrosion resistance and adaptability in the harsh environment could be significantly improved.

Microstructure and corrosion resistance of chromate conversion coating on cold sprayed aluminum alloy 2024

This paper examines the microstructure and corrosion resistance of chromate conversion coating (CCC) on cold sprayed (CS) aluminum alloy 2024. CCC is an effective surface treatment for aluminum aircraft alloy to improve paint adhesion as well as corrosion resistance. Although the studies of CCC on wrought aluminum alloy have been extensively conducted, understanding the interaction of CCC applied to CS deposits has not yet been addressed in the literature. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and focused ion beam (FIB) were employed for investigating the microstructure of CCC on CS2024 deposits. Potentiodynamic testing, electrochemical impedance spectroscopy (EIS), and immersion testing were performed to probe into corrosion performance of CCC on CS deposit. The results demonstrated that unique intermetallic networks inside the CS deposit formed CCC with more heterogeneous microstructure compared to CCC on wrought counterparts. Although wrought and CS 2024 presented similar corrosion resistance within a short exposure time (<48 h), CCC on CS deposits was more susceptible to corrosion damage, revealed by EIS with an extended exposure time (>48 h). Additionally, distinctive corrosion propagation of CCC on CS deposits along intermetallic networks and prior particle boundaries was seen from the immersion test.

LDH conversion films for active protection of AZ31 Mg alloy

• Zn−Al and Li−Al LDHs with Li-, Mo- and W-based corrosion inhibitors were prepared. • Zn−Al LDH W and Li−Al LDH Li showed the highest corrosion resistance. • XRD, FTIR and XPS analysis confirmed the incorporation of inhibitors. • Active corrosion properties were confirmed by SVET analysis for the Zn−Al LDH W layer. • An inhibition corrosion mechanism is proposed based on several phenomena. Zinc aluminium (Zn-Al) and lithium aluminium (Li-Al) – layered double hydroxides (LDH) coatings with incorporated inhibitors (Li−, Mo− and W−based) were successfully synthesized on AZ31 Mg alloy. Zn−Al LDH W and Li−Al LDH Li showed the highest corrosion resistance and were selected for further evaluation. SEM cross−section examination revealed a bi−layer structure composed of an outer part with loose flakes and a denser inner layer. XRD, FTIR, and XPS analysis confirmed the incorporation of the inhibitors. Post−treatments with corrosion inhibitors containing solutions resulted in the selective dissolution of the most external layer of the LDH coating, reducing the surface roughness, hydrophilicity and paint adhesion of the layers. Active corrosion properties were confirmed by SVET evaluation for the Zn−Al LDH W coating. The proposed active corrosion mechanism involves the ion−exchange of aggressive Cl − ions, deposition of hydroxides and competitive adsorption of W−rich corrosion inhibitors.

Coal tar-derived conductive pigment/polyvinylidene fluoride composite for Joule heating

The fast-increasing demand for high-performance carbon conductive paints has motivated the use of inexpensive precursors and easy-to-manufacture methods to scale up production. The performance of carbon conductive paints highly depends on the precursor types, carbonization conditions and the coordination between carbon pigment and binder. This work investigated the effect of precursors (by-products of coking industry including coal tar pitch, anthracene oil, naphthalene oil, and washing oil) on the structure and properties of carbon pigment, as well as the influences of binders polyvinylidene fluoride (PVDF), styrene-butadiene emulsion, and acrylic emulsion on the electrothermal properties and adhesion of carbon paint coating. The conductive pigment prepared from coal pitch has nano-sheet structure, high sp2 content, large sp2 cluster size and high disordered structure, resulting high carrier concentration and mobility, and low volume resistivity. The carbon conductive coating fabricated from coal pitch-based pigment and PVDF (PC-PVDF) has good electrothermal properties, excellent stability, low volume resistivity, good adhesion and corrosion resistance. The electrical conductivity of carbon-PVDF composites prepared from coal tar pitch, anthracene oil, naphthalene oil, and washing oil as precursors were 15.7, 3.0, 4.4, and 4.0 S/m, respectively. Coal pitch-derived conductive pigment-PVDF carbon coating exhibits excellent Joule heating performance, i.e., up to 147 °C at 20 V when heating at 122 °C/min, uniform temperature distribution, and excellent reusability. This work demonstrates the potential application of coal pitch-based pigment-PVDF coating for Joule heating.

Influence of Zinc Coatings Mechanical Pre-Treatments for the Formation of Environmentally Friendly Passivation Duplex Anti-Corrosion Systems

Abstract The paper content is focused on the various evaluation methods of mechanical pre-treatment of hot-dip galvanized surface performed in order to increase the organic paint adhesion (both synthetic and waterborne). Emphasis was placed on low volatile organic compounds (VOC) values in coating systems. Corrosion degradation of the tested coatings was also monitored. The mechanical surface pre-treatment was performed using a standard technology, so-called sweeping, with synthetic corundum with F40 grain size (these samples served as a standard). Alternative methods that can be used in operations without blasting equipment were also investigated. These included regrinding with two different grain sandpapers (P40 and P100) and regrinding with a corrosion resistant steel brush (wire diameter 0.3 mm). The surface texture was evaluated in accordance with the ČSN EN ISO 4287 standard. Corrosion-mechanical resistance was evaluated by a pull-off adhesion test (according to the ČSN EN ISO 4624 standard) and in a salt spray environment (according to the ČSN EN ISO 9227 standard). Based on the obtained results, mechanical pre-treatment with a corrosion resistant steel brush and possibly P100 grit sandpaper can be recommended, as pre-treatment with these tools showed statistically the best corrosion-mechanical properties.

Synthesis and characterization of polymerizable surfactants based on ethoxylate alcohol cinnamate for emulsion polymerization

A new polymerizable surfactant (surfmer) has been synthesized by esterification of (cinnamic acid) with nonionic surfactant (alcohol ethoxylate). The chemical structure of the prepared nonionic surfmer was characterized by mass spectroscopy. The surface-active properties of the prepared surfmer alongside its self-assembly properties were investigated by measuring electrical conductivity, The measured critical micelle concentration (CMC) of (EO/PO) cinnamate (surfmer) was (0.01mol/L). The order of the polymerization reaction for surfmer was found to be 1.3 and 2.8 using vinyl acetate (VAc) monomer and butyl acrylate (BuA) respectively; the rate of the reaction was faster in case of (BuA) at the same reaction conditions. The rate of conversion of (BuA) was slightly affected by increasing the surfmer concentration however the (VAc) shows a greater reduction of the rate of conversion by increasing the surfmer concentration. the morphology of poly(BuA) particles show more polydispersity and poly(VAc) looks nearly monodisperse better morphology (more defined and spherical particles) with this surfmer more than poly(BuA) at the same conditions. The number of polymer particles Nt was found to increase by increasing surfmer concentration. Increasing the surfmer concentration decreases the surface charge density for both Poly(VAc) and poly(BuA) particles, however, the lattices produced using prepared surfmer show good mechanical stability. Industrial application of prepared poly(VAc) homopolymer using the surfmer as a wood adhesive and the co-polymers latex of poly (VAc/BuA) in paint was carried out and compared with similar commercial types, from the results it was clear that superior properties of adhesion properties, water resistance in wood glue, on the other hand, great improving paint adhesion and washability and water-resistant of the paint for the emulsion latex prepared using cinnamate surfmer.

Surface quality of laser paint removal of marine steel: a comparative study using a Gaussian beam and a flat-top beam.

The spot mode has a great influence on the effect of laser paint removal, but it has not been clarified. This paper studies the influence of a Gaussian beam and a flat-top beam on surface quality. The results show that for the laser paint removal with the Gaussian beam, the surface hardness, corrosion resistance, and adhesion of marine steel improved significantly. The surface hardness increased by a factor of 20.8% compared to the original substrate, and the paint adhesion increased by 32.7%. For the flat-top beam, the surface quality of the substrate is unchanged, but the cleaning efficiency was observed to be 20% higher than that of the Gaussian beam. This paper can provide technical support for the control of surface cleaning quality in the laser paint removal process.

Permanganate loaded Ca-Al-LDH coating for active corrosion protection of 2024-T3 alloy

Ca-Al-Layered Double Hydroxide (Ca-Al-LDH) coating was explored on 2024-T3 aluminium alloy by in situ growth methodology following a 1 h treatment at atmospheric pressure. Mn-based species were successfully incorporated into the Ca-Al-LDH structure by a low-temperature post-treatment (Ca-Al-LDH-Mn). Both LDH coatings disclosed a flaky-like morphology and low thickness (~0.6 µm). Ca-Al-LDH-Mn coating showed optimal paint adhesion and the highest long-term corrosion resistance in 3.5 wt% NaCl solution. Evaluation of scribed LDH specimens by SEM/EDS techniques up to 7 days of immersion in 3.5 wt% NaCl solution revealed that the presence of Mn species in the Ca-Al-LDH-Mn provided active corrosion protection.

Investigation of anodised surface complexity and its correlation with surface hydrophilicity using fractal analysis

Anodising is a process of developing oxide coating on surface of metal electrolytically to improve its corrosion resistance. However, there has been inadequate research on the impact of the anodised surface characteristics on hydrophobicity or hydrophilicity. Surface roughness and porosity are often used to quantify surface characteristics, while each alone could not be enough to reflect all complexity of the surface. Hence, the fractal theory utilised to quantify the complexity of the anodised surface and decode its relation with the hydrophobicity or hydrophilicity of the surface. In this study, experiments of anodising for aluminium 6061 were carried out with three concentrations of electrolyte (3.5, 2.5 and 1.5 mol) and three current densities (1.0, 1.5 and 2.0 A/dm2). In addition, the surface characteristics after anodising was studied by using Scanning Electron Microscopy (SEM) analysis. Furthermore, surface roughness measurement was performed to obtain the surface roughness profile for fractal analysis. Moreover, a hydrophobicity test was implemented on anodised samples to obtain the contact angle between the water droplet and the surface. The outcomes showed that higher fractal dimension of anodised surface resulted in a smaller contact angle presenting a more hydrophilic surface. Furthermore, anodised samples with higher current density and concentration of electrolyte will result in higher fractal dimension and hence lower contact angle indicating the anodised surface will become more hydrophilic. Therefore, it is shown that measurement of fractal dimension is a reliable indicator for predication of surface wettability after anodising in order to improve the paint adhesion.

Evaluation of Conversion Coatings Without Hexavalent Chromium for Aerospace and Defense Applications

Conversion coatings containing hexavalent chromium are currently used in aerospace and defense manufacturing on various aluminum alloys to provide corrosion protection and enhanced adhesion of subsequent coatings. However, hexavalent chromium is toxic to humans with negative health effects from acute and chronic exposure. Regulatory mandates have accelerated a global effort to replace hexavalent chromium-containing materials because of their toxicity. A consortium was established to evaluate safer conversion coating materials, including the chemical processing of the surfaces prior to applying the conversion coatings. Four conversion coatings without hexavalent chromium were compared against a hexavalent chromium-based conversion coating for the following tests: coating weight, electrical contact resistance, paint adhesion, bare and painted neutral salt fog corrosion tests, painted SO2 salt fog corrosion test, and painted outdoor beachfront corrosion test. The test results for the four conversion coatings without hexavalent chromium were encouraging since several candidates exceeded some of the specification requirements or consortium expectations. In particular, the Socosurf TCS/PACS conversion coating performed well in the coating weight, electrical contact resistance, paint adhesion, and corrosion tests. The results of this evaluation provide significant progress toward providing a replacement material for a traditionally hexavalent chromium material application on aluminum.

OPTIMASI SETTING PARAMATER CLEANLINESS, KETEBALAN, DAN JENIS CAT PADA MATERIAL BAJA A572 TERHADAP DAYA REKAT CAT

The manufacturing process consists of several stages, one of them is the finishing stage. The finishing stage at PT. Supra Surya Indonesia consists of surface preparation process and painting process. The adhesion of the paint must meet the criteria to get good protective quality for the product. In the painting process, there are always defective products that must go through the repair stage before packing. Process parameters such as cleanliness level of the material surface and paint thickness need to be considered and the selection of the type of paint will affect the results of painting. Based on the problems above, it is necessary to research the analysis of process parameters that can optimize the value of paint adhesion. This study uses the Taguchi method so that the contribution of cleanliness parameters is 49.6995 %, paint thickness is 5.0014 %, and paint type is 40.4139 %. The optimum combination of parameters is cleanliness Sa 2 1/2, the thickness of 100 µm, and the type of phenolic epoxy paint.

Surface Characteristics and Corrosion Behavior of Carbon Steel Treated by Abrasive Blasting

The effects of blasting with metallic steel grit and non-metallic alumina grit on steel surface characteristics were evaluated. These abrasives are generally used at construction sites and in vacuum blasting. Milled steel specimens were used to investigate the effect of the blasting conditions on surface properties. The effect of difference in surface properties on the adhesion strength and corrosion behavior were measured through adhesion tests, polarization curves, and electrochemical impedance spectroscopy. The limitations of blasting were evaluated using corroded steel specimens, as were the effects of corrosion products, salts, and abrasive material remaining on the blasted steel surface on the adhesion and corrosion resistance of paint. Steel grit more effectively increased the surface roughness than alumina grit; however, with both abrasive materials, the roughness increased with the blast projection angle. However, in the case of alumina grit, some abrasive material remained on the surface; thus, the actual roughness not including the residual abrasive material was more complex and greater than that of the sample blasted with steel grit. According to the adhesion strength test of painted and unpainted specimens, the adhesion force improved with increasing surface roughness and residual abrasive materials. Further, surface roughness was linearly correlated with the adhesion strength of unpainted specimens for both abrasive materials with blasting, and the adhesion strength force with alumina grit was approximately 1.4 times higher than that with steel grit, suggesting that increased roughness and residual abrasive material could benefit adhesion. According to the electrochemical test results, lower roughness and increased residual abrasive material owing to alumina grit on the steel surface enhanced the surface corrosion resistance, confirming the benefit of residual materials. Grinding left behind corrosion products and salts under the steel, resulting in the recurrence of rusting. However, the residue from blasting with alumina suppressed corrosion, thus improving the adhesion and corrosion resistance of the paint.

Effect of cerium (IV) on thin sulfuric acid anodizing of 2024-T3 alloy

Chromic acid anodizing (CAA) is still being used today for corrosion protection of fatigue-critical components in the aeronautic industry due to the lack of feasible alternatives. Ce-containing sulfuric acid anodizing (SAA) has been identified as a promising strategy for the development of alternatives to toxic CAA. This work explores thin sulfuric acid anodizing (TSAA) focusing on the following effects: (i) current density and voltage values; (ii) concentration of Ce(IV). Screening of the optimum combination in search of minimum thickness and the best corrosion resistance was performed using electrochemical impedance spectroscopy (EIS). Two Ce-containing anodic films were selected and further investigated in comparison with the inhibitor-free film in terms of morphology (FEG-SEM, TEM), composition (RBS), corrosion resistance (EIS, NSST), high-cycle fatigue and paint adhesion. The results indicate that the path to approach the CAA performance lies through thin (<1 μm) SAA-Ce films formed at low current density.

Adhesion of water-based paint on plasma-treated high-density polyethylene sheets

In this study, high-density polyethylene (HDPE) surfaces were treated with plasma to enhance the adhesion of a water-based paint. A custom-built cold atmospheric pressure plasma jet (CAPPJ) device using a neon transformer as its power source was developed and used in the surface treatment. The jet nozzle of the device was made from polytetrafluoroethylene with two bare stainless-steel electrodes positioned laterally through the nozzle and opposite each other with a 1 mm gap. Gas was allowed to pass through the nozzle, exiting through a 1 mm diameter hole where a plasma jet is ejected through the arc from the electrodes. The effect of plasma treatment on HDPE surfaces was determined. Air and nitrogen were used as the process gases and exposure times were also varied. Hydrophilicity of the surface increased with longer plasma exposure with a corresponding 50% increase in surface free energy compared to the untreated surface. From Fourier transform infrared and x-ray photoelectron spectroscopy analysis, it was seen that plasma treatment introduced oxygen containing functionalities onto the surface. Increase in adhesion of a water-based paint was observed for plasma-treated HDPE sheets.

What Happens to Wood after a Tree Is Attacked by a Bark Beetle?

Advancing climate change is affecting the health and vitality of forests in many parts of the world. Europe is currently facing spruce bark beetle outbreaks, which are most often caused by wind disturbances, hot summers, or lack of rainfall and are having a massive economic impact on the forestry sector. The aim of this research article was to summarize current scientific knowledge about the structure and physical and mechanical properties of wood from bark beetle-attacked trees. Spruce stands are attacked by a number of beetles, of which Ips typographus is the most common and widespread in Central Europe. When attacking a tree, bark beetles introduce ophiostomatoid fungi into the tree, which then have a greater effect on the properties of the wood than the beetles themselves. Fungal hyphae grow through the lumina of wood cells and spread between individual cells through pits. Both white rot and brown rot fungi are associated with enzymatic degradation of lignin or holocellulose, which is subsequently reflected in the change of the physical and mechanical properties of wood. Wood-decay fungi that colonize wood after infestation of a tree with bark beetles can cause significant changes in the structure and properties of the wood, and these changes are predominantly negative, in the form of reducing modulus of rupture, modulus of elasticity, discolouration, or, over time, weight loss. In certain specific examples, a reduction in energy consumption for the production of wood particles from beetle-attacked trees, or an increase in surface free energy due to wood infestation by staining fungi in order to achieve better adhesion of paints or glues, can be evaluated positively.

SURFACE FREE ENERGY AND FLEXURAL PROPERTIES OF WOLLASTONITE FILLED POLYPROPYLENE COMPOSITES

Nowadays, appearance is an important factor in vehicles. For this reason, paint application is widely used in plastic parts. Surface energy is a key parameter for the adhesion of paint on the surface of polymers. Among thermoplastic polymers, polycarbonate and acrylonitrile butadiene styrene are commonly used materials due to their higher surface energies. For low surface energy materials, surface energies can be increased using streamer, plasma, corona, mechanical etching and chemical etching methods. The aim of this work is to eliminate the pre-treatments applied to parts produced with polypropylene (PP) polymer using wollastonite (CaSiO3) additive. For this purpose, CaSiO3 filled PP composites containing 40 wt.% wollastonite with different sizes and coatings were produced by extrusion process. Afterwards, plate samples were prepared from granules using a hot pressing device. Flexural properties and surface free energy measurements were performed on these composites produced in plate form. From the results, an increased surface free energy was observed for small particle size and aminosilane coated wollastonite added PP composite with an increase by 23% of the total surface free energy. Flexural strengths were well correlated with the surface free energy results and showed an increase by 1.2% for the same additive.

Multiscale and Multi-Technical Approach to Characterize the Hot-Dip Galvanized Steel Surface and Its Consequence(s) on Paint Adhesion and Tendency to Blistering

It is well known that the surface state (cleanliness, composition) of galvanized steel prior to the application of an organic coating is an important parameter. The surface state will affect the adhesion properties of the complete system and therefore will also impact its corrosion resistance and its tendency to blistering. Before the application of a pretreatment layer, galvanized steel strips are normally alkaline cleaned. This step is known to remove the native oxide film formed on hot dip galvanized steel after processing and appears as one of the most important steps to study the impact of the surface properties on the performance of painted systems. This study focused on making use of the cleaning step to input a variability on the surface composition (mainly surface concentration of aluminum) and evaluate its consequence(s) on the performance of a complete paint system. The results showed that, a variability in terms of surface aluminum concentration could be achieved by the cleaning step and that signs of performance improvement in terms of adhesion and tendency to blistering were spotted with a low content of aluminum at the surface.

Ca-based sealing of plasma electrolytic oxidation coatings on AZ91 Mg alloy

Plasma electrolytic oxidation (PEO) coatings on AZ91 Mg alloy were sealed in calcium nitrate solutions at different pH values (3, 4 and 5). Sodium dodecyl sulfate (SDS) was added to study the effect of SDS on the corrosion resistance of the sealed coatings. The microstructure, chemical composition and corrosion resistance of the coatings were investigated by means of SEM, XPS, XRD and electrochemical corrosion tests. The corrosion performance of the coatings was improved due to precipitation of Ca-containing precipitate. Low pH and SDS addition enhanced hydroxyapatite precipitation and produced hydrophobic coatings with worse paint adhesion but better corrosion resistance.

Improving fire retardancy of unheated and heat-treated fir wood by nano-sepiolite

The effects of nano-sepiolite (NS) on fire properties of unheated and heat-treated fir wood were studied using a newly developed apparatus. Separate sets of specimens were prepared to be painted with plain acrylic-latex paint and NS-treated paint as well. Heat treatment of specimens was carried out in a laboratory oven at 185 oC and under atmospheric air pressure. Six fire properties were measured including times to onset of ignition and glowing, as well as back-darkening and back-holing times. Two properties of mass loss and burnt area were measured once the fire was extinguished and the test on each specimen terminated. Results demonstrated significant improvement in fire properties of NS. The improvement was partially attributed to the mineral nature of sepiolite with low chemical reactivity, acting as an insulating layer towards the penetration of fire to the wood substrate. The improvement in fire properties was also partially attributed to the high thermal conductivity coefficient of sepiolite, delaying the accumulation of heat at the point nearest to the piloted fire to reach ignition point. Heat treatment did not significantly affect fire properties in unpainted specimens. However, fire properties in the painted heat-treated specimens (with both plain paint, and NS-treated paint) tended to decrease, though the values were still significantly higher than those of unpainted heat-treated specimens. FTIR spectra illustrated significant alteration in intensities at wave numbers 3100 cm−1 and 1,00 cm−1, related to the hydroxyl groups of cell-wall polymers (mostly hemicelluloses). These alterations had a negative effect on the adhesion of the water-based paint used in this study. It was concluded that nano-sepiolite has a promising future as a fire retardant. However, as cost is of vital importance for paint manufacturers, further studies on the effects of sepiolite at micron-scale available at a lower price should also be carried out.

Resistance to artificial daylight of paints used in urban artworks. Influence of paint composition and substrate

Solar radiation is one of the deterioration factors par excellence of modern urban artworks, as among other manifestations, it causes loss of colour. This deterioration can compromise the durability of the works, although it is not known to what extent this durability can vary depending on the substrate supporting the paint. We evaluated the susceptibility to sunlight of 10 paints of differing compositions as typically used by urban artists, by exposing them, applied to concrete and brick, to artificial sunlight ageing test in laboratory conditions. Colour changes over time were studied, along with mineralogical (x-ray diffraction), chemical (scanning electron microscopy-energy dispersive x-ray spectroscopy) and physical (contact angle and peeling tests) changes. The durability of the paints on these substrates depends mainly on the paint composition (base, pigment and filler) but also on the type of substrate, as this influences paint adhesion capacity. The greatest colour modification was detected in fluorescent paints, which lose colour due to degradation of the organic phase, and with aggravation of defects during drying, eventually detach from the substrate.