Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

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A local company instituted a new chemical procedure in their spray phosphating system used in the pretreatment of large components for industrial racking systems. An inorganic conversion coating is deposited on the workpiece surface during phosphating and this prepares the surface to receive an organic top-coat. The organic coating is applied to the workpiece surface in the form of a powder and cured to form a continuous film about 80 u.m thick. The solution chemistry of the phosphating system was monitored by sampling and chemical analysis and taking direct reading instrumental measurements on the process and rinse solutions. The process was also evaluated using the results of a waste minimisation audit. This involved gathering data on composition, flow rates and costs of inputs and outputs of the process. Two types of information were collected and used during the audit, namely chemical monitoring (concentration levels of Na, Fe, Zn, Mo, Mn and Cr and measurements of conductivity, TDS, SS and pH) and water usage data on the Phosphating Line and existing data (raw materials, workpieces and utility inputs as well as domestic waste, factory waste and scrap metal outputs). The data were analysed using four established waste minimisation techniques. The Scoping Audit and the Water Economy Assessment results were determined using empirically derived models. The Mass Balance and the True Cost of Waste findings were obtained through more detailed calculations using the results of the chemical analysis. The results of the audit showed that the most important area for waste minimsation in the Phosphating Line was the (dragged-out phosphating chemicals present in) wastewater stream. According to the scoping audit, water usage had the third highest waste minimisation potential behind powder and steel consumption for the entire powder coating process. While the scoping audit and the specific water intake value showed that water consumption for the process was not excessive, it did not indicate that the pollution level in the rinse waters was high. Further, drag-out calculations showed that drag-out volumes were typical of those found in the metal finishing industry. However the presence of high levels of metal species in the rinse waters was highlighted through the chemical monitoring of the Phosphating Line. The True Cost of Waste Analysis estimated potential financial savings for the effluent stream at about R8000 for a period of 105 days. However this does not take into consideration the cost of the liability associated with this stream when exceeding effluent discharge limits (given in the Trade Effluent Bylaws) or of the chemical treatment necessary to render this stream suitable for discharge to sewer. Intervention using only "low-cost-no-cost" waste minimisation measures was recommended as a first step before contemplating further areas for technical or economic feasibility studies. However, a further study involving monitoring the sludge was recommended in order to establish the potential financial savings offered by this waste stream. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

Zinc phosphate conversion coating has been applied to improve the corrosion resistance and paint adhesion. However, zinc phosphate crystals dissolve in a highly alkaline environment, which reduces the corrosion resistance of base metal. To improve the phosphate stability in a highly alkaline environment, a post-rinse treatment has been applied to phosphate coating by rinsing with an aqueous solution which contains certain anions or cations. Chromatepost-rinse treatment is the most widely used method and has shown a great improvement in corrosion resistance. But, due to the environmental problems caused by chromate ions, non-chromate post-rinse treatment should be developed, which has equal or better corrosion resistance than does chromate post-rinse treatment. In this research, inorganic silicate with addition of Ca²⁺, Ba²⁺, Ni²⁺, Mg²⁺, has been extensively evaluated together with silane solution, γ -aminopropyltriethoxysilane ( γ -A.P.S., NH₂(CH₂)₃Si(OC₂H₅)₃), which was applied after the post-rinse treatment. The evaluation was carried out by the highly advanced surface analysis techniques such as SEM/EDX, AES, SIMS, and XRD and polarization measurements. / Master of Science

L'objectif de cette thèse est de créer de nouvelles surfaces nanostructurées avec des revêtements bioactifs et d'étudier leurs propriétés physico-chimiques afin de développer de meilleurs modèles d'implants dentaires et d'optimiser leur ostéo-intégration. Cette fonctionnalisation a été réalisée en deux étapes ; on a commencé par la nano structuration de la surface de TiO2 par anodisation pour créer des sites réactifs sur les bords extérieurs des nanotubes qui agissent comme des points d'ancrage du revêtement bioactif et améliorent le verrouillage mécanique entre le revêtement et le substrat. Ensuite, la modification chimique est réalisée par revêtement de la surface nanostructurée avec des revêtements bioactifs de phosphate de calcium (CaP) et phosphate de calcium dopé par strontium (Sr.CaP). Ce revêtement a été réalisé par électrodéposition pulsée. La caractérisation physico-chimique par MEB, XPS et IR a montré que le dopage avec Sr favorise un composé non-apatitique similaire à DCPD ou DCPA (Dicalcium Phosphate Dihydrate ou Anhydrous), tandis que le revêtement de CaP non-dopé ressemble à un composé d'apatite amorphe ACP. L'addition de strontium s'offre le double avantage de favoriser les mécanismes de la croissance cellulaire et d'obtenir une phase inorganique avec de bio-performances meilleurs que les composés apatitiques. Nous avons également évalué les propriétés d'adsorption de ces surfaces fonctionnalisées en étudiant l'adsorption des protéines (BSA).Cette adsorption a été réalisée sur nanotubes fonctionnalisés vierges, nanotubes enrobés avec CAP et CAP dopé Sr et elle a été évalués selon le temps de déposition et la valeur du pH de la solution qui affecte la charge de la protéine et de la surface. L'évaluation cinétique et structurelle révèle diffèrent géométries d'adsorption en fonction du pH, du temps d'adsorption et aussi en fonction de la nature chimique de la surface. Ces résultats de l'adsorption et conformation de protéine forment une base de données pour comprendre et contrôler ses activités et réactions avec le vivant lorsqu'elle est utilisée dans le system des implants dentaires / The objective of this thesis is to create new nanostructured surfaces with bioactive coatings and to study theirs physicochemical properties in order to develop better dental implants designs and promote their osseointegration. This functionalization was performed in two steps; starting by the nanostructuration of TiO2 surface by anodisation to create reactive sites on the edges of titanium nanotubes which acts as points of “attachment" to bioactive coatings. The second step was the surface chemical modification by coating the nanostructured surface with bioactive coatings of calcium phosphate (CaP) and strontium doped calcium phosphate (Sr.CaP). This coating was performed by pulsed electrodeposition. The physicochemical characterization by XPS, SEM and IR showed that doping with Sr promotes a non-apatitic compound similar to DCPD or DCPA (Dicalcium Phosphate Dihydrate or Anhydrous), while undoped CaP coating looks like an amorphous apatite-like compound ACP. The addition of strontium has the double advantage of optimizing the cellular multiplication and of giving an inorganic phase with bio-performance better than apatitic compounds. We also evaluated the adsorption proprieties of these functionalized surfaces by investigating the adsorption of proteins (BSA). This adsorption was performed onto tblank nanotubes, nanotubes coated with CaP and Sr doped CaP and evaluated according to deposition time and to the pH value of the solution that affect both protein and surface charge. The kinetic and structural evaluation reveals different adsorption geometries according to pH and adsorption time and also according to the chemical nature of surface. Such results of protein adsorption and conformation may form a database to understand and control protein activities and reactions with living body when used for dental implants system

The main objective of the master’s thesis is to study the influence of phosphate coating structure on the mechanical properties of screw connection. The theoretical part describes the conventional phosphating process and it is followed by an analysis of current knowledge of phosphating technology. Experiments are carried out on screw valves mounted to a high pressure diesel pump by Bosch Diesel s.r.o., made of unalloyed carbon steel. To investigate the effect of the structure on the connection sealing, twelve kinds of phosphate coatings varying in one process parameter were prepared. The monitored parameters determining the phosphate structure are – type of phosphate and activation bath, its temperature and concentration and time of immersion. The sealing connection is examined during simulated assembly process by angle controlled tightening while measuring torque and permanent material deformation. Prepared layers are characterized by determination of weight per unit area and their structure observed by electron microscope.