Adhesion Of Organic Coatings Research Articles

Physical ageing effect on water uptake and adhesion of epoxy coatings by EIS and the blister test

In a previous work, it was shown that the physical ageing of organic coatings had a strong effect onto the water uptake process, leading to lower water uptake values at saturation. The service life of an organic coating can be related to the water content at saturation, that may induce corrosion of the substrate, but also to the adhesion that prevents direct contact between the substrate and the aggressive environment. In this work, the effect of physical ageing onto water uptake and adhesion of epoxy coatings onto aluminium is then investigated.A model epoxy coating (DGEBA/Jeffamine230) was applied onto aluminium panels and fully cured using adequate thermal cycles. Different amounts of physical ageing were created by controlling the cooling of the systems and measured thanks to modulated differential scanning calorimetry (MDSC). The coated panels were then immersed in sodium chloride solution (30 g.L − 1) at different ageing temperatures. The water uptake was calculated using EIS thanks to the Brasher and Kingsbury relation and the diffusion coefficients were evaluated using the dual-Fick diffusion model.For different values of physical ageing and different amounts of water uptake, the adhesion was evaluated using the blister test method. The obtained results allow to discuss the effect of physical ageing onto the water uptake content and the adhesion of organic coatings.

Life evaluation of organic coatings on hydraulic metal structures

This paper presents the effects of tensile stress and corrosion environment on the protective performance of organic coatings on hydraulic metal structures. Accelerated ageing tests are performed on the organic coatings for 3600 h in UV-condensation test chambers and under immersion conditions. Gloss loss, color difference, thickness, rust area and adhesion of organic coatings are investigated. Acceleration coefficient between the accelerated ageing tests and the natural ageing environment are discussed based on the corrosion degree comparison method. The results show that corrosion degree of the coatings increases with the prolonging of the test time. Coatings are corroded more seriously in salt water than that in fresh water. Tensile stress accelerates the corrosion process of the organic coatings, and the corrosion degree of the organic coatings increases with the increase of stress levels. The corrosion process of the organic coatings could be divided into two stages: first stage is the time from the beginning to the appearance of rust; second stage is the time from the appearance of rust to the 5% of rust area rate. The gloss loss rate is chosen to evaluate the corrosion behavior of the coatings in the early stage, while the rust area rate is chosen to evaluate the corrosion behavior of the coatings in the middle and later stage. A life evaluation model of the organic coatings on hydraulic metal structures is established based on the acceleration coefficient. The influences of corrosion environment and tensile stress on the coating life are considered via the gloss retention coefficient and the corrosion inhibition coefficient in the model.

CORROSION PROTECTION OF CARBON STEEL USING ZIRCONIUM OXIDE/SILANE PRETREATMENT AND POWDER COATING

Surface pretreatment plays important role in improvement of corrosion resistance and adhesion of organic coatings. A new generation of metal pretreatments based on nanosize zirconium oxide or ogranosilane film has been investigated recently as an alternative method to phosphatation. In this paper, ZrO2/silane composite film on carbon steel was prepared and characterised by field emission scanning electron microscopy, energy dispersive X-ray spectrum and electrochemical measurements. The effect of ZrO2/silane surface treatment on the protection properties of powder coating was studied by salt spray test and adhesion measurement. The results obtained showed that ZrO2 was rapidly precipitated on the steel surface after first 1 minute immersion and ZrO2/silane film formed after 4 minutes immersion give best protective properties. Powder coating on carbon steel with ZrO2/silane pretreatement has equivalent protection performance like powder coating with phosphate pretreatment.

Influence of Hot-Dip Galvanised Coating Morphology on the Adhesion of Organic Coatings Depending on the Zinc Bath Pb Content and the Postgalvanising Cooling Method

Hot-dip galvanised coatings used either alone or with an organic coating (duplex system) constitute an effective anticorrosion protection. Adhesion between the coating and the zinc substrate plays a vital role in the durability of the duplex system. Conditions of the galvanising process and alloying additives incorporated into the zinc bath influence mechanical and protective properties as well as thickness, structure, and surface morphology of the zinc coatings. The influence of the surface morphology of zinc coatings on the adhesion of organic coatings was studied. The tests were carried out on zinc coatings produced in baths with varying Pb content and by employing various cooling methods after the galvanising process. It was noted that a rapid cooling in water produces zinc coatings with a fine-grain structure, more suitable for paint application compared to the air-cooled ones, with a spangle.

Review—Conversion Coatings Based on Zirconium and/or Titanium

There is a growing interest in conversion coatings based on titanium and/or zirconium as the result of the health and environmental issues associated with legacy chromate and phosphate conversion coatings. Any alternative technology should be environmentally friendly and cost effective, and also able to achieve comparable corrosion resistance and paint adhesion for ferrous and non-ferrous substrates. Conversion coatings based on titanium or zirconium seem to fulfill many of these requirements and thus offer a great potential for further applications. This literature review summarizes the scientific results in this rapidly growing area of research. Following the description of composition of conversion bath and deposition mechanism, the effects of process parameters for conversion baths such as pH, temperature, immersion time and agitation are presented together with coating characteristics. The effects of the type of substrate and substrate pre-treatment are explored for the most-studied substrates: Al alloys, zinc-coated steels and steels. Properties such as composition, morphology and thickness are summarized. The corrosion performance of the conversion coatings is discussed, as well as adhesion of organic coatings and delamination mechanism for a full coating system including substrate/coating/top-coat.

Properties of FA-CVD silica coated steel sheet after deformation: coating integrity and corrosion related forming limit curve

Thin silica coatings may be used as pretreatments for steel sheet, offering temporary corrosion protection and promoting adhesion of organic coatings. For use as ready to paint product, silica coated steel has to possess also good corrosion properties after deformation and successive paint application. In this paper, we investigate the forming limit curve for flame assisted chemical vapour deposited silica coated steel sheet with respect to corrosion properties after paint application. We find good corrosion properties up to a strain of 10%, indicating a high tolerance towards deformation. Evaluation of the silica coated steel sheet by scanning electron microscopy shows that severe failure takes place at high levels of deformation, but only at a fraction of the surface. Adhesion, cracking as well as deadhesion and flaking of the very thin films (15–50 nm) was furthermore investigated by scratch testing.

Effect of surface pretreatment on water absorption and wet adhesion of organic coatings

A study has been conducted on the effects of surface pretreatment with 3-aminopropyltriethoxysilane (3-APS) on the water absorption and adhesion behaviour on mild steel and glass substrates of two commercial organic coatings, one an alkyd coating and the other a two pack epoxypolyamide coating. The results have shown that using 3-APS for surface pretreatment before coating results in a significant reduction of total water absorption for both coating systems on a glass substrate. However, for the mild steel substrate, treatment with 3-APS reduces water absorption using an alkyd system, but increases it in the epoxy system. The results also indicate that using 3-APS for pretreatment enhances the overall wet adhesion performance for alkyd coatings on steel and epoxy and alkyd coatings on glass substrates but not for epoxy on steel. These data are consistent with the known adsorption behaviour of 3-APS on steel, i.e. as an easily hydrolysed hydrogen bond to the amine group, rather than as the more stable metal–oxide–silicon bond.

Fracture Mechanical Testing of Adhesion of Organic Coatings on Aluminium

Applicability of the wedge test and the accompanying fracture mechanical data analysis, commonly used for testing of adhesively bonded joints, was inestigated in an attempt to develop a quantitative laboratory test for evaluating paint adhesion on aluminium. The test was further used, along with a relatively better accepted laboratory test for filiform corrosion of painted aluminium to study the mutual effects of corrosion and adhesion of various pretreatments and paint systems on extruded AA 6082 T6 aluminium alloy. Pretreatments used were commercial processes for deoxidising, chromating, hot AC anodising and Ti/Zr conversion coating. The paints were polyester TGIC and epoxy DICY, both pigmented commercial products. In particular, the compatibility of pretreatment-paint combinations were investigated The wedge test methodology and sample preparation developed proved to be a satisfactory approach for quantitative evaluation of pretreatment-paint combinations for aluminium. Ti/Zr treatment gave exceptionally good adhesion and corrosion results when coated with polyester. Epoxy coated Ti/Zr bars failed completely. However, hot AC anodising, although in general significantly more robust than Ti/Zr, was more compatible with the polyester than polyester coating. With the advent of chromate-free pre-treatments, the need to establish the compatibility of the modified aluminium surface and applied organic coating was demonstrated.

The Effect of Surface Pretreatment on Water Absorption and Wet Adhesion of Organic Coatings

A study was conducted on the effects of surface pre-treatment with 3- aminopropyltriethoxysilane (3-APS) on the water absorption and adhesion behaviour of two commercial alkyd and epoxy polyamide organic coatings on mild steel and glass substrates. The results indicated that using 3-APS as surface pre-treatment prior to coating resulted in a significant reduction of total water absorption for alkyd on both mild steel and glass substrate. Subsequently ile adhesion of alkyd is enhanced on both pre-treated mild steel and glass substrate. However 3-APS pre-treatment of mild steel increases water absorption of epoxy and lowers its adhesion strength. While 3-APS pre-treatment of glass reduces water absorption of epoxy and subsequently enhances the overall wet adhesion. These data are consistent with the known adsorption behaviour of 3-APS to steel, i.e. as an easily hydrolysed hydrogen-bond to the amine group, rather than as the more stable metal-oxide-silicon bond.

Silanes and rare earth salts as chromate replacers for pre-treatments on galvanised steel

Cr(VI)-based pre-treatments have been in use for long time on several materials, however, they are target of great criticism and in the near future they could be definitely banned. The actual alternatives to Cr(VI) show pros and cons when sets of key properties are considered such as: corrosion resistance, adhesion of organic coatings, fatigue resistance, reliability and quality control. However, some of the possible alternatives show high potential, if some improvements are carried out and the if mechanisms involved are more deeply understood. The present work focus on the use of rare earth (Ce, La) salts and bis-sulphur silane (BTESPT) as chromate substitutes for galvanised steel. These compounds when applied by immersion and subsequent curing originate films that improve corrosion resistance and paint adherence. The films were characterised by Auger and XPS spectroscopy. The corrosion resistance was assessed by electrochemical impedance spectroscopy and dc polarisation. Comparison with the chromate conversion pre-treatment is also carried out simultaneously with discussion of the possible mechanisms involved in the different processes.

Adhesion of epoxy to hydrotalcite conversion coatings: I. Correlation with wettability and electrokinetic measurements

Hydrotalcite (HT) based conversion coatings are being developed as an environmentally benign alternative to chromate conversion coatings. This examination investigates the relationship between the interlayer oxoanion in the HT structure and surface chemistry, and their subsequent effect on adhesion of organic coatings. The interlayer ions examined included nitrate, carbonate and persulfate. Dry and wet-state adhesion of 25–75 μm thick epoxy films were measured by the pull-off tensile strength. The results were compared with surface energy and isoelectric point measurements using the rising height method and electrophoresis of HT powders, respectively. The Lifshitz–van der Waal (LVW)/Lewis acid–base approach was employed for analysis of contact angle data. It was observed that the HTs with greater LVW bonding had better wet-state adhesion, while a reciprocal relationship was seen between dry state adhesion and the isoelectric point. The correlations with the dry and wet state adhesion are interpreted as indicating that dry state adhesion is optimized by minimizing unfavorable polar interactions between the basic epoxy and HT interfaces. Wet state adhesion, where polar interactions are disrupted, is dictated by non-polar bonding.

Effect of the chemical modification of the precursor of ZrO2 films on the adhesion of organic coatings

ZrO2 films were deposited on low carbon steel by a sol-gel process as a chemical pretreatment before the application of a polyester paint. The films were obtained by a dip-coating technique using solutions of Zr(OBun)4 containing complexing agents (acetylacetone or acetic acid). These additives modified the alkoxide at the molecular level, so a new precursor was formed in solution. This new compound shows slower rates of hydrolysis and condensation than Zr(OBun)4, which allows the stability of solutions and the morphology of the gel to be controlled. Moreover, the length and the temperature of the thermal treatment influence the structure of the gel by reducing the amount of organic residues. The behavior of the films in promoting the adhesion of organic coatings was evaluated by measuring the detachment of the paint from a cross-scratch of samples which had been exposed for different times in a salt fog chamber. Tests using electrochemical impedance spectroscopy were also carried out. According to the results, most of the samples pretreated with zirconia layers showed a good performance, even better than commercial chemical treatments, when acetic acid was used as a modifier of the alkoxide precursors.

Acid‐Base Properties of Passive Films on Aluminum: I. A Photoelectrochemical Study

The acid‐base properties of aluminum surfaces have recently attracted much interest due to their consequences on the adhesion of organic coatings. The present work deals with a novel photoelectrochemical approach to the acid‐base properties of aluminum surfaces. Passive films were considered here as wide‐gap semiconductors. When they are in contact with an electrolyte, a space charge builds up. A negative (positive) space charge is considered here as a sign of an electron donor (acceptor) surface, i.e., to a Lewis basic (acid) surface. The more negative (positive) the space charge or the corresponding band bending in the semiconductor, the more basic (acid) the passivated surface. The spectrophotoelectrochemical response of the samples polarized at the rest potential under ultraviolet illumination allowed the measurement of the band bending as the difference between the thresholds of two photoemission phenomena from the Fermi level toward the passive film conduction band at the inner and outer interfaces of the passive films. Negative band bendings were always obtained, evidencing the basic character of the analyzed surfaces. A basicity scale was obtained which is compared in Part II to that deduced from X‐ray photoelectron and X‐ray absorption near‐edge structure studies.

The effect of temperature development during stone impact on damage morphology and adhesion of organic coatings

The influence of the heat generation induced by stone impact events is shown to be significant for the damage process of organic coatings. Experimental results on different water-soluble coatings are presented, indicating a rise in surface temperature of more than 80°C during single impacts with kinetic energies of more than 0.01 J. This temperature dissipates within a few tens of milliseconds. The damage morphology is determined by brittle fracture processes and plastic deformation effects in the case of low and high impact induced temperatures, respectively.

特集／有機皮膜の密着性 表面・界面制御技術から見た有機皮膜の密着性

特集／有機皮膜の密着性 表面・界面制御技術から見た有機皮膜の密着性

特集／有機皮膜の密着性 高分子・金属接着界面の量子化学

特集／有機皮膜の密着性 高分子・金属接着界面の量子化学

特集／有機皮膜の密着性 高分子のレオロジーと接着

特集／有機皮膜の密着性 高分子のレオロジーと接着

特集／有機皮膜の密着性 金属と高分子材料接着系における密着性評価方法

特集／有機皮膜の密着性 金属と高分子材料接着系における密着性評価方法

Effect of Zeta Potential on Adhesion of Organic Coatings

Abstract The force of adhesion of an aqueous phase (pH 9.6 borate) to steel in the presence of a xylene solution of hydroxy-terminated polybutadiene increases below the potential of zero charge (−550 mV vs Ag/AgCl). Incorporation of a high molecular weight quaternary ammonium cation in the xylene phase inhibits displacement of the organic phase at cathodic potentials. These results suggest that cathodic polarization of steel below the potential of zero charge can initiate cathodic disbonding. The disbonding will then irreversibly propagate by the alkaline attack of the cathodic electrolysis product on the organic film.

The effect of water on the adhesion of organic coatings on aluminium

Water normally decreases the strength of adhesive joints. In the case of epoxy coatings on aluminium, however, after an initial decrease the adhesive strength increased with the time of exposure to water. It is suggested that this increase is caused by the hydration of aluminium oxide adjacent to the adhesive joint, thus enabling additional hydrogen bonding between the organic coating and its support. Results obtained by measuring adhesion with peel and tape tests on aluminium foil and an alloy with different surface pretreatments and different curing conditions have been compared. It is shown that the tape test is useful for the semi-quantitative determination of the stability towards water of an adhesive joint.