Surface Treatment Of Aluminum Research Articles

RESEARCH ON THE PROPERTIES OF THERMAL SPRAYED NI-CR-SI-FE-B COATINGS / TERMINIU BŪDU UŽPURKŠTŲ NI-CR-SI-FE-B DANGŲ SAVYBIŲ TYRIMAS

The article deals with the flame sprayed Ni-Cr-Si-Fe-B coating on aluminum alloy substrates. Before the thermal spraying process, aluminum samples were modified applying chemical, mechanical and thermal processing pre-treatment methods. The main aluminum surface treatment was removing an oxide layer from the surface and improving the exploitation properties of nickel-based coatings. The work involved coating microstructure, porosity, adhesion and microhardness tests. The dependence of the estimated exploitation properties of flame spray coatings on aluminum surface preparation methods and technological parameters of spraying has been established. Santrauka Straipsnyje nagrinėjamos liepsniniu būdu ant aliuminio lydinių substratų užpurkštos Ni-Cr-Si-Fe-B dangos. Aliuminio bandiniai prieš terminį purškimą buvo apdoroti cheminiais, mechaniniais ir terminiais būdais. Pagrindinis aliuminio paviršiaus apdorojimo tikslas buvo pašalinti oksidų sluoksnį nuo paviršiaus ir pagerinti nikelio pagrindo dangų eksploatacines savybes. Atlikti dangos mikrostruktūros, porėtumo, adhezijos ir mikrokietumo tyrimai. Nustatyta liepsninio purškimo būdu gautų dangų eksploatacinių savybių priklausomybė nuo aliuminio paviršiaus paruošimo būdų ir purškimo technologinių parametrų.

Preparation & Microscopic Characterization of Non-Chrome Chemical Conversion Film in Aluminum Surface

A chromium-free environmental protection aluminum surface treatment technology was developed by theoretical analysis and a large number of experiments. Add zirconium ions and cerium ions to the treatment solution, besides adding fluoride, aluminum and hydrogen peroxide, etc. According to the orthogonal test obtained a non-chromate film-formation process of environmental friendly aluminum. The characterization methods including SEM, XPS and XRD were applied to study and analyze the morphology, composition, phase, and corrosion resistance of phosphate film, then discussed the film-forming reaction mechanism. Results showed that chemical conversion film formed on the aluminum surface was uniform, compact and stronger anti-corrosion could replace the traditional, more toxic chromate conversion film.

Vibrational spectroscopic studies of triethoxy(4-(trifluoromethyl)-phenyl) silane and its sol–gel coating

We have prepared a silica sol–gel using triethoxy (4-(trifluoromethyl)-phenyl) silane (TETFMPS) as a precursor in ethanol solution under acidic condition. The prepared sol–gel was applied to the surface treatment of aluminum for corrosion prevention. Infrared and Raman spectra of the silane coupling agent, sol–gel and sol–gel films on metal have been collected. Infrared spectroscopy has been used to study the thermal effect on the chemical composition of xerogel. Results suggested that TETFMPS molecule has a Cs point group symmetry with the plane of reflection orthogonal to the phenyl ring and the organic part of the sol–gel film remains essentially unchanged at or below 450°C but decomposes at or above 550°C. After the decomposition of the organic branch, the remaining film is composed of silica. Vibrational assignments were suggested by using the collected spectroscopic data in different states along with the group vibrational frequencies and other related references.

Aluminum surface treatment by the RF plasma pencil

The effects of atmospheric RF plasma treatment on aluminum sheets were studied. The treatment was performed with the plasma pencil developed at Masaryk University, using Ar and Ar/O2 gas mixtures. The surface free energy of treated sheets increased up to 72.6mJ/m2, which later resulted into higher adhesion between the STEEL industrial protective varnish and the plasma treated aluminum sheets. The adhesion properties were tested by ISO-certified Erichsen and bending tests. A set of IR spectroscopy measurements in ATR mode proved significant plasma surface cleaning, generation of OH groups and surface oxidation. The addition of O2 into the Ar flow resulted in stronger oxidation of aluminum, which was measured by the EDX technique. The surface of aluminum sheets became porous after the plasma treatment with Ar. The smoothening of pores occurred after adding a small amount of O2 into the Ar flow.

Aluminum Surface Treatment for Improved Bonding of Magnesium/ Aluminum Bi-Metallic Casting

Magnesium/aluminum bi-metallic castings offer significant mass saving opportunities in automotive structural applications. A “zincate+galvanizing” surface treatment has been developed for aluminum alloys to provide improved wetting and metallurgical bond with molten magnesium in bi-metallic casting, due to the removal of Al2O3 layer and the formation of with a very thin metallic zinc film on the aluminum surfaces. The bi-metallic experiments using a selfdesigned high-vacuum test apparatus provided valuable understanding of the interfacial phenomena of Mg (AM60)/ Al (6061) bi-metallic samples. The test results show significantly improved shear strength in the bi-metallic samples with “zincate+galvanizing” surface treatment. It is recommended to adjust the pre-heating temperature and time of the aluminum substrates to control the interfacial reactions for optimum interfacial properties in the actual bi-metallic casting processes.

Effect of Different Aluminium Surface Treatments on Ice Adhesion Strength

Excessive ice accumulation on power network equipment can affect their integrity and cause damage with serious socioeconomic consequences. To mitigate that, de-icing techniques (mechanical or thermal) have been developed, but these techniques are often limited in their application and are generally expensive and time consuming. Recently, companies and research groups have focused on the development and application of icephobic coatings such as superhydrophobic materials intended to drastically reduce ice adhesion force on exposed equipments. The aim of this paper is the examine the influence of aluminium surface treatments on ice adhesion. Preparation of new and various aluminium surface treatments as well as the need to improve the knowledge of the mechanisms involved in ice adhesion are part of this research. Depending of the type of materials, surface roughness can either promote the formation of air pockets within pores or between coating surface asperities (low adhesion strength), or it can create ice mechanical anchoring if water partially or totally penetrates the porosity. Aluminium anodization using phosphoric acid was studied. Surface morphology was evaluated using scanning electron microscopy and measurements of ice adhesion strength were performed using a centrifuge technique. Based on these results, several surface treatments of aluminium have been considered including aluminium anodizing with partial Al2O3 etching followed by different sealing steps using hydrophobic polymer compounds such as polytetrafluoroethylene.

Photodegradation of Orange II solutions by TiO 2 active layers jet sprayed on aluminium sheets

In this work, active TiO 2 layers have been immobilized, on aluminium sheets, by a common and cheap deposition technique: jet spray. The layers’ adhesion to the substrate was achieved by mixing the titania with a commercial thermally adherent polyester ink, which is industrially used for aluminium surface treatment (lacquering). The layers’ photocatalytic performance was tested in the degradation of the organic dye Orange II in aqueous solutions, in a batch photoreactor under visible and solar light, and compared with TiO 2 (anatase) suspensions. The layers’ photocatalytic behaviour was evaluated taking into account different experimental variables, such as: (i) layer thickness; (ii) operation time; (iii) TiO 2/polyester ink weight ratio and (iii) dye solution concentration and pH. A better performance was attained for layers having a 1:1 weight ratio of TiO 2 and polyester ink and a thickness of 60 μm (100 g/m 2). These layers showed an interesting discolouration performance: an attenuation degree of 95% and discolouration rate, assuming an apparent first order reaction, reaching 2.2 × 10 −3 min −1. These results were attained for the naturally resulting dye solution pH of ≈7, and for the lowest dye concentration of 20 mg/L. Therefore, neither alkalinisation or acidification of the dye solution nor the utilization of high-concentration solutions is recommended. Despite the slower kinetics, the dye degradation level achieved is similar to that obtained for TiO 2 powder suspensions. Thus, these treated layered aluminium pieces can be considered as a serious alternative to photocatalytic suspensions of the oxide, with the advantage of excluding the removal of the photocatalyst at the end of the process.

Influence of plasma surface treatment on bond strength behaviour of an adhesively bonded aluminium-epoxy system

Aluminium-epoxy systems are widely studied for uses as adhesive structural bonding. When an amine hardener is used as a curing agent for an epoxy resin, interactions between the hardener and the aluminium create a volume called an interphase, whose properties are distinct from the bulk resin and has a significant influence on the adhesive bond strength. This article reports on the influence of an aluminium surface treatment on the interphase formation and adhesive bond strength. The aluminium surface was degreased with acetone, and then the surface was activated by means of atmospheric plasma treatment with different nitrogen/oxygen gas mixtures. The characterization of the aluminium surface chemistry and surface energy was determined by X-ray photoelectron spectroscopy (XPS) and a sessile drop test, respectively. The interphase formation was investigated by means of X-ray energy dispersion spectrometer (EDS) in a low vacuum scanning electron microscopy (LVSEM). Adhesive bond strength was measured by tensile testing of a single lap aluminium-epoxy-aluminium assembly. Atmospheric plasma treatment showed an improvement of the thermo-mechanical properties of the assembly. Several points were discussed to explain the effect of atmospheric plasma treatment on the adherence and on the interphase formation.

The influences of surface treatment and gas annealing conditions on the inversion behaviors of the atomic-layer-deposition Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitor

The inversion behaviors of atomic-layer-deposition Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitors are studied by various surface treatments and postdeposition annealing using different gases. By using the combination of wet sulfide and dry trimethyl aluminum surface treatment along with pure hydrogen annealing, a strong inversion capacitance-voltage (C-V) response is observed, indicating a remarkable reduction in interface trap state density (Dit) at lower half-part of In0.53Ga0.47As band gap. This low Dit was confirmed by the temperature independent C-V stretch-out and horizontal C-V curves. The x-ray photoelectron spectroscopy spectra further confirm the effectiveness of hydrogen annealing on the reduction of native oxides.

Aluminium removal from wastewater by refused beach cast seaweed. Equilibrium and dynamic studies

Aluminium removal has been investigated in synthetic and real wastewaters provided by an aluminium surface treatment plant. Marine algae, obtained as beach cast seaweed (a refuse substance) were used as adsorption material. The influence of pH, metal concentration and time for aluminium elimination was studied by use of synthetic solutions. The optimum pH value was 4.0, which provided a maximum adsorption capacity of 22.5 mg g(-1). The adsorption percentage surpassed 80% in less than 30 min of contact time. Real solutions from the industrial unit were fully characterized and tested in two different fixed-bed columns. One column was filled with 27.5 g of dried beach cast seaweed. Three cycles of adsorption and two of desorption were carried out. The first cycle (12 mg g(-1) maximum sorption capacity) was enough to reach the maximum adsorption capacity at 15 mL min(-1) flow rate. The second column was packed with 1100 g of seaweed and its behaviour was compared to another column filled with activated charcoal, following both the same experimental procedure. Maximum sorption capacity was 14 mg g(-1) for seaweed, whereas the activated charcoal only reached 1.6 mg g(-1) (flow rate of 250 mL min(-1)).

Strength Prediction and Experimental Validation of Adhesive Joints Including Polyethylene, Carbon-Epoxy and Aluminium Adherends

Polyolefins are especially difficult to bond due to their non-polar, non-porous and chemically inert surfaces. Acrylic adhesives used in industry are particularly suited to bond these materials, including many grades of polypropylene (PP) and polyethylene (PE), without special surface preparation. In this work, the tensile strength of single-lap PE and mixed joints bonded with an acrylic adhesive was investigated. The mixed joints included PE with aluminium (AL) or carbon fibre reinforced plastic (CFRP) substrates. The PE substrates were only cleaned with isopropanol, which assured cohesive failures. For the PE CFRP joints, three different surfaces preparations were employed for the CFRP substrates: cleaning with acetone, abrasion with 100 grit sand paper and peel-ply finishing. In the PE AL joints, the AL bonding surfaces were prepared by the following methods: cleaning with acetone, abrasion with 180 and 320 grit sand papers, grit blasting and chemical etching with chromic acid. After abrasion of the CFRP and AL substrates, the surfaces were always cleaned with acetone. The tensile strengths were compared with numerical results from ABAQUS® and a mixed mode (I+II) cohesive damage model. A good agreement was found between the experimental and numerical results, except for the PE AL joints, since the AL surface treatments were not found to be effective.

Durability Improvement of Co-cured Carbon/Epoxy Composite-Aluminum Laminate With Nano-size Carbon Black at Cryogenic Temperature

Since metal foils such as aluminum, copper or nickel foils have been used in composite structures for radiation shielding and EMI protection in space environments, high adhesive bonding strength and durability between metal foils and composites under large temperature variations are very important. In this study, the strength of co-cure bonded joint between an aluminum foil and a composite has been investigated, with three different aluminum surface treatments such as standard PAA (Phosphoric Acid Anodization) procedure, abrasion with sandpaper, and carbon black pasting on the metal foils. From the double cantilever beam (DCB) tests, it was found that the interlaminar peel strength with carbon black pasting improved 60% compared to the laminate without any surface treatment. Also it was found that the interlaminar peel strength of the co-cure carbon/epoxy composite-aluminum foil hybrid laminate with the carbon black pasting on the aluminum foil did not decrease after many thermal cycles from 30°C to –196°C.

Shock activation of α-alumina from calcinated Al-rich sludge

Enormous quantities of Al-sludge from aluminum surface treatments are yearly generated all over the world. Despite of being known as important supplier of alumina, the Al-sludge also have some other components that need to be removed. Calcination has revealed to be an inevitable treatment to achieve such objective. It was also found that conventional densification processes are not efficient for this kind of powders and, to overcome that difficulty, a dynamic compaction approach, using detonation generated shock waves have been followed. The calcinated powders compacted by this way have shown up values of density and hardness, after sintering, comparable to the ones of commercial alumina processed by the conventional methods.

Infrared and Raman spectra of triacetoxyvinylsilane, aqueous sol–gel and xerogel

Triacetoxyvinylsilane (TAVS) has been used as a precursor to prepare sol–gel under aqueous conditions. The sol–gel product has been applied for the surface treatment of aluminum. Infrared and Raman spectra have been collected for TAVS and for TAVS sol–gel, xerogel and sol–gel-coated aluminum. Vibrational analyses have been suggested for the recorded spectra based essentially on the group frequencies and the spectral variation with the change of the sol–gel product states and the vibrational assignments of similar molecules. From the recorded infrared and Raman spectra of the sol–gel and xerogel, it is found that the sol–gel produced in the process with TAVS is essentially the same as that prepared from vinyltriethoxysilane. Thermo-gravimetric analysis (TGA) of TAVS xerogel has been conducted, and an explanation has been given in coordination with the results obtained from IR spectroscopic study of the xerogels cured at different temperatures. The study has demonstrated the thermal effect on the condensation of the sol–gel process and on the vinyl decomposition of TAVS xerogel.

Anodizing – A Key for Surface Treatment of Aluminium

This article describes the flexibility and the potentials of the most important finish for aluminium-based materials. After a suggestion for the classification of anodizing processes, the historical development of the electrolytic anodic oxidation (EAO) and the plasma-electrolytic anodic oxidation (PAO) are presented. In the following section the focus is given on selected topics concerning the process parameters, the microstructure including the layer composition and properties. The variability of the anodizing process parameters and the used materials provide this variety of application. Furthermore, both differences and similarities of the EAO and PAO processes are shown. The conclusion of this review emphasizes that there is still some need for further research especially in the interaction of the process, the formed microstructure and the resulted properties determining the final application. Hence new possibilities for this surface treatment will be open.

An environmentally friendly coating for corrosion protection of aluminum and copper in sodium chloride solutions

Triacetoxyvinylsilane (TAVS) has been used as precursor to prepare sol–gel under aqueous conditions for the surface treatment of aluminum and copper metals. The corrosion behavior of the sol–gel-treated metals has been investigated with cyclic voltammetry, potentiodyamic polarization and electrochemical impedance spectroscopy. Results from the electrochemical measurements have shown that the TAVS sol–gel-coated metal provided a better corrosion protection than the triethoxysilane (TES) sol–gel-coated metal due to the hydrophobic nature of vinyl group. Contact angle measurements have been conducted and the results have been applied to explain the degree of the corrosion protection of the coating film.

Laser treatment of aluminum surface: Analysis of thermal stress field in the irradiated region

Laser surface treatment of aluminum is considered and the temperature as well as the stress fields developed in the laser irradiated region are predicted using the finite element method (FEM). The predictions are obtained for two laser pulses with different pulse lengths. In the simulations, the variable thermal properties of the substrate material are used. The experiment is conducted to treat the aluminum specimen surface with the laser beam. The laser output pulse intensity consists of repetitive pulses, which are used in the model study to examine the metallurgical changes in the irradiated region. SEM and XRD are carried out in this regard. It is found that the von-Mises stress reaches the maximum in the surface vicinity, particularly at the onset of cooling cycle starts. The von-Mises stress attains values less than the critical values for the crack formation, which is particularly true after the end of the cooling cycle. The residual stress formed in the surface region is in the order of a few MPa.

Nitrogen ion implantation for improvement of the mechanical surface properties of aluminum

The results of the surface treatment of commercial aluminum by nitrogen ion implantation at 120 keV and implanted fluences ranging from 3×l0 17 to 1.1×10 18 ions/cm 2 are reported. The treatment was found to lead to the formation of the hexagonal phase AIN, a decrease in strain and an increase of crystallite sizes. The modification of the surface layer so produced was thought to be a cause of a measured increase in surface microhardness and corresponding decrease in friction coefficient and wear measured in pure methanol. Oxygen found in the surface layers was also thought to play a significant role in determining tribological performance.

Modeling of Wound Coaxial Blumlein Pulsers

Blumlein pulsers are well-suited devices for high-voltage pulse generation in nanosecond and microsecond ranges. These generators have been used with great success in several areas such as in breakdown tests, X-ray generation, lasers, and high-energy plasma implantation. They consist of lengths of transmission lines charged in parallel and synchronously discharged in series into the load by using single or multiple switches at the opposite line endings. The main problem with the device performance is the presence of the shield cable impedance contributing to the Blumlein power loss especially when using only one switch. The very well known technique used for minimizing these losses consists of winding the transmission lines to increase the line shielding inductance if coaxial cables are used. Therefore, herein, circuit models are presented to assess theoretically the temporal response of the wound coaxial Blumlein pulsers by using a SPICE circuit simulator. For model assessment, the authors used the experimental results produced by a wound coaxial Blumlein pulser of 100 kV/200 A with 1.0 mus of pulse duration constructed for applications in surface treatment of polymers and aluminum with high-energy ions

The Role of the Residual Stresses of the Epoxy-Aluminum Interphase on the Interfacial Fracture Toughness

When an epoxy-diamine system (DGEBA-IPDA) is applied onto aluminum alloy (5754) and cured, an interphase having chemical, physical, and mechanical properties quite different from those of the bulk polymer is created between the substrate and the part of the polymer having bulk properties. To get a better understanding of the role of the interphase on the interfacial fracture toughness either a tri-layer (bulk coating/interphase/substrate) or a bi-layer model (bulk coating/substrate) were used for quantitative determination of the critical strain energy release rate (noted Gc). Indeed, as the interphase formation results from both dissolution and diffusion phenomena, we were able to control the interphase formation within coated systems by controlling the liquid-solid contact time and then to make tri- or bi-layered systems. The particularity of models used is to consider residual stress profiles developed within the entire system leading to an intrinsic parameter representing the work of adhesion between the polymer and the metallic substrate. The aim of this publication is to clearly establish the role of the interphase mechanical properties, such as Young's modulus and residual stress on the interfacial fracture toughness. Results are presented and discussed for three different aluminum surface treatments (chemical etching, degreasing and anodizing).