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Pure magnesium (Mg) and its alloys with calcium (Ca) and both Ca and zinc (Zn) have potential as bioresorbable bone implant materials provided the corrosion rate can be controlled. Thus, corrosion behaviour was investigated for pure Mg, Mg-2Ca, and Mg-2Ca-1Zn cast alloys subjected to either no heat treatment or to solutionizing and aging heat treatment. In addition, corrosion behaviour was investigated for surface modifications involving the deposition of silver (Ag) nanoparticles. These materials and constructs were all nominally biocompatible in that they would not elicit a strong and immediate adverse tissue reaction when implanted in bone. Static immersion tests in Hanks’ balanced salt solution were performed to evaluate the corrosion behaviour. The Mg-2Ca alloy exhibited the highest corrosion rate when compared with pure Mg and Mg-2Ca-1Zn for any length of immersion time. For short immersion times (48 hours), solutionizing followed by natural aging reduced the corrosion rate of Mg-2Ca alloy, but this heat treatment did not seem to have an effect on the corrosion rate of Mg-2Ca-1Zn alloy. As well, for short immersion times (48 hours), solutionizing and artificial aging also did not seem to have a large effect on corrosion rates for either Mg-2Ca or Mg-2Ca-1Zn, when compared to solutionizing and natural aging. Corrosion behaviour of surface-modified samples was sensitive to certain features of the Ag depositions. It was found that when the deposited Ag tracks were thick and wide, the corrosion rate of Ag-deposited samples increased significantly when compared to samples without any Ag deposition. However, when the Ag tracks were thinner and somewhat narrower, the corrosion rate did not appear to be much higher than that of samples without Ag deposition. Therefore, controlled Ag deposition may not be too detrimental to the corrosion behaviour of Mg and Mg alloys. The corrosion product morphology appeared to be similar for both the samples deposited with Ag and samples without any Ag. Needle-like formations were observed in small areas on the corroded surfaces. X-ray diffraction revealed Mg(OH)₂ as the main corrosion product. Because energy dispersive X-ray analysis consistently revealed multiple elements in the corrosion products (such as Mg, O, Ca, P, small amounts of C, and sometimes Cl), it was concluded that other compounds (possibly hydroxyapatite, magnesium chloride, and/or magnesium- and calcium-containing phosphates) may have formed in addition to the Mg(OH)₂.

Pure magnesium (Mg) and its alloys with calcium (Ca) and both Ca and zinc (Zn) have potential as bioresorbable bone implant materials provided the corrosion rate can be controlled. Thus, corrosion behaviour was investigated for pure Mg, Mg-2Ca, and Mg-2Ca-1Zn cast alloys subjected to either no heat treatment or to solutionizing and aging heat treatment. In addition, corrosion behaviour was investigated for surface modifications involving the deposition of silver (Ag) nanoparticles. These materials and constructs were all nominally biocompatible in that they would not elicit a strong and immediate adverse tissue reaction when implanted in bone. Static immersion tests in Hanks’ balanced salt solution were performed to evaluate the corrosion behaviour. The Mg-2Ca alloy exhibited the highest corrosion rate when compared with pure Mg and Mg-2Ca-1Zn for any length of immersion time. For short immersion times (48 hours), solutionizing followed by natural aging reduced the corrosion rate of Mg-2Ca alloy, but this heat treatment did not seem to have an effect on the corrosion rate of Mg-2Ca-1Zn alloy. As well, for short immersion times (48 hours), solutionizing and artificial aging also did not seem to have a large effect on corrosion rates for either Mg-2Ca or Mg-2Ca-1Zn, when compared to solutionizing and natural aging. Corrosion behaviour of surface-modified samples was sensitive to certain features of the Ag depositions. It was found that when the deposited Ag tracks were thick and wide, the corrosion rate of Ag-deposited samples increased significantly when compared to samples without any Ag deposition. However, when the Ag tracks were thinner and somewhat narrower, the corrosion rate did not appear to be much higher than that of samples without Ag deposition. Therefore, controlled Ag deposition may not be too detrimental to the corrosion behaviour of Mg and Mg alloys. The corrosion product morphology appeared to be similar for both the samples deposited with Ag and samples without any Ag. Needle-like formations were observed in small areas on the corroded surfaces. X-ray diffraction revealed Mg(OH)₂ as the main corrosion product. Because energy dispersive X-ray analysis consistently revealed multiple elements in the corrosion products (such as Mg, O, Ca, P, small amounts of C, and sometimes Cl), it was concluded that other compounds (possibly hydroxyapatite, magnesium chloride, and/or magnesium- and calcium-containing phosphates) may have formed in addition to the Mg(OH)₂.

De nombreux secteurs industriels ont besoin de matériaux métalliques avec des propriétés de résistance à l'usure et de résistance à la corrosion dans des environnements agressifs ou à des températures élevées très élevées. Ces propriétés spécifiques, notamment mécaniques, électriques, magnétiques et optiques, peuvent être obtenues par la production de couches métalliques. Les revêtements d’alliage ou de métal nanocristallin offrent les caractéristiques de performance souhaitées.L'électrodéposition est un procédé largement utilisé pour fabriquer des revêtements sur des substrats métalliques. La structure et les propriétés des revêtements nanocristallins Co-Mo en font des matériaux prometteurs pour diverses applications. De nos jours, les alliages à base de cobalt sont utilisés dans les avions, l’automobile et l’électronique en raison de leur facilité d’utilisation. En outre, les alliages de cobalt sont largement étudiés en raison de leur utilisation prometteuse pour remplacer les alliages nocifs pour l'environnement dans le corps humain. Les alliages nanocristallins sont utilisés dans de nombreux secteurs industriels, tels que la biologie, l'énergie, la nanotechnologie, l'aviation et bien d'autres.Le but de ce travail est de produire des revêtements nanocristallins de Co-Mo électrodéposés et d'étudier l'effet de la microstructure sur leur résistance à la corrosion dans des solutions physiologiques simulées.Le travail est divisé en cinq chapitres:• Chapitre I. Bibliographie. Aspects métallurgiques de l’ingénierie des surfaces métalliques pour les revêtements nanocristallins de Co-Mo.Dans ce chapitre, les aspects métallurgiques de l’ingénierie de surface des revêtements nanocristallins de Co-Mo sont présentés sur la base des données de la littérature. Différentes méthodes utilisées pour le dépôt de revêtements métalliques sont discutées.• Chapitre II. Echantillons et méthodes et techniques expérimentales.Ce chapitre présente les conditions expérimentales d'électrodéposition pour les revêtements nanocristallins de Co-Mo et les techniques utilisées pour les caractériser.• Chapitre III. Structure, propriétés mécaniques et comportement électrochimique des revêtements nanocristallins Co-Mo.Ce chapitre présente la structure, les propriétés mécaniques et le comportement électrochimique des revêtements nanocristallins Co-Mo déposés sur du cobalt pur.• Chapitre IV. Co-Mo / TiO2 revêtements nano-composites.Ce chapitre présente la structure, les propriétés mécaniques et le comportement à la corrosion des revêtements nano-composites Co-Mo / TiO2 galvanisés sur du cobalt pur.• Chapitre V. Mécanismes de croissance des revêtements nano-composites Co-Mo / TiO2.Ce chapitre étudie la structure des revêtements nanocomposites Co-Mo / TiO2 électrodéposés pour des temps d'électrodéposition courts et longs dans des conditions potentiostatiques sur des électrodes ayant la forme d’un film ou d’un disque.En résumé, des revêtements nanocristallins Co-Mo et des revêtements nanocomposites Co-Mo / TiO2 ont été obtenus par dépôt électrochimique. Leur structure et l'influence de différentes conditions d'électrodéposition sur leur structure ont été étudiées. Leur résistance à la corrosion a été testée dans des solutions physiologiques simulées. De plus, le mécanisme de croissance des couches a été déterminé sur les deux types d'électrodes.Cette thèse a été réalisée sous la forme d'une coopération en Cotutelle entre l'Université des sciences et technologies AGH Stanisław Staszic à Cracovie et l'Université de Bourgogne à Dijon pour promouvoir les relations scientifiques franco-polonaises. Ce travail a été soutenu financièrement par le gouvernement français et l'ambassade de France en Pologne. / Currently, various methods are used in surface engineering for the production of surface layers and coatings on many metal substrates to improve their performance. Different industry sectors are oriented to increase the wear resistance and corrosion resistance of materials that are used in aggressive environments or work at high temperatures. Specific properties, including mechanical, electrical, magnetic and optical, can be achieved by the production of metallic layers. Nanocrystalline and amorphous metal or alloy coatings are unique and offer the desired performance characteristics. They are often characterized by very high strength, associated with the effect of strengthening the edge grain.Electrodeposition is a widely used method of producing coatings on metallic substrates. The structure and properties of Co-Mo nanocrystalline coatings make them promising materials for various applications. Nowadays, cobalt based alloys are used in aircraft, automotive and electronics due to their good usability. In addition, cobalt alloys are widely studied due to their promising use in replacing alloys harmful to the environment or the human body. Nanocrystalline alloys are used in many industrial sectors, such as biology, energy, nanotechnology, aviation and many others.The aim of this work is to obtain electrodeposited Co-Mo nanocrystalline coatings and to investigate the effect of microstructure on their corrosion resistance in simulated physiological solutions.The work is divided into five chapters:• Chapter I. Bibliography. Metallurgical aspects of metal surface engineering for Co-Mo nanocrystalline coatings.In this chapter, metallurgical aspects of surface engineering of Co-Mo nanocrystalline coatings are presented on the basis of literature data. Various methods used for deposition of metallic coatings are discussed.• Chapter II. Samples and experimental methods and techniques.This chapter presents experimental electrodeposition conditions for Co-Mo nanocrystalline coatings and techniques used to characterize them.• Chapter III. Structure, mechanical properties and electrochemical behavior of Co-Mo nanocrystalline coatings.This chapter presents the structure, mechanical properties and electrochemical behavior of nanocrystalline Co-Mo coatings deposited on pure cobalt.• Chapter IV. Co-Mo / TiO2 nano-composite coatings.This chapter presents the structure, mechanical properties and corrosion behavior of Co-Mo / TiO2 nano-composite coatings electroplated on pure cobalt.• Chapter V. Growth Mechanisms of Co-Mo / TiO2 nano-composite coatings.This chapter investigates the structure of Co-Mo / TiO2 nanocomposite coatings electrodeposited for short and long electrodeposition times under potentiostatic conditions on the electrode from pure cobalt-shaped cobalt and pure cobalt electrode in the form of a wire.In summary, nanocrystalline Co-Mo coatings were obtained by electrochemical deposition as well as Co-Mo / TiO2 nano-composite coatings. Their structure and the influence of different electrodeposition conditions on the structure were investigated and their corrosion resistance was tested in simulated physiological solutions. In addition, the mechanism of layer growth was determined on two types of electrodes: a disk-shaped electrode and a wire-shaped electrode.This thesis was carried out in the form of Cotutelle cooperation between the AGH University of Science and Technology Stanisław Staszic in Krakow and the University of Burgundy in Dijon to promote Polish-French scientific relations. This work was financially supported by the French government and the French Embassy in Poland.

Hořčík a kompozity fosforečnanu vápenatého jsou slibnými materiály pro biodegradabilní a nosné implantáty určené pro regeneraci kostí. Předložená práce je zaměřena na návrh, zpracování a charakterizaci vnitřně propojených kompozitů hořčíku s fosforečnanem vápenatým (Mg/CaP). Fosforečnany vápenaté jako jsou hydroxyapatit (HA), kalcium-deficitní hydroxyapatit (CDHA) a fosforečnan vápenatý (TCP) byly syntetizovány a použity pro výrobu skafoldů s kontrolovanou porozitou pomocí metody robocastingu. Byly připraveny porézní předlisky s ortogonální mřížkou a s vnitřními makropóry o velikosti ~500 µm, které byly následně slinovány za teploty 1100 °C po dobu 5 hodin. Vnitřně propojené Mg/CaP kompozity byly připraveny infiltrací čistého hořčíku a hořčíkových slitin obsahujících malá množství vápníku nebo zinku, například 0,2 hm.% vápníku a 1 hm.% zinku do porézních keramických skafoldů. Infiltrace byla provedena pomocí námi vyvinuté a nově popsané metody známé jako “Proudem asistovaná slinovací infiltrace” (z angl. Current Assisted Metal Infiltration (CAMI)). CAMI metoda umožňuje do 15 minut infiltrovat porézní keramický předlisek roztaveným kovem. Pulzujícím elektrickým proudem bylo dosaženo rychlého tavení a následného tuhnutí Mg/CaP kompozitů. Fyzikálně-chemické vlastnosti finálních vnitřně propojených kompozitů byly stanoveny pomocí rastrovací elektronové mikroskopie, počítačové mikro-tomografie, rentgenové difrakční analýzy a optické mikroskopie za účelem stanovení fázové distribuce a interakce mezi materiály. Kromě toho byla u připravených kompozitů hodnocena jejich mechanická pevnost v tlaku, degradační rychlost pomocí různých metod a biokompatibilita spolu s pokusem o uvedení těchto typů materiálů jako potenciálních degradabilních biomateriálů určených pro výrobu desek a/nebo šroubů pro ortopedické aplikace.

M.Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology / Corrosion responses of some carbon steels, stainless steel and copper alloys in the presence of a culture of bacteria (referred to as SRB-Sulphate-reducing bacteria) found in industrial heat exchangers, was studied to recommend best alloys under this service condition, with techno-economic consideration. Water from cooling towers in three plants in a petrochemical processing complex were analysed for SRB presence. Two of the water samples showed positive indication of SRB presence. The mixed cultures obtained from plant one were grown in prepared media and incubated at 35 °C for 18 days. Potentiodynamic polarisation studies in anaerobic conditions were done on the selected alloys in aqueous media with and without the grown SRB. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were then used to study the corrosion morphology and corrosion products formation. The voltamograms show higher icorr for alloys under the SRB compared to the control media, indicating the SRB indeed increased the corrosion rates. The surface analysis showed pitting on steel alloy ASTM A106-B. Localised attack to the grain boundaries on a selective area, was seen on ASTM A516-70 dislodging the grains, and intergranular corrosion was seen throughout the exposed area of ASTM A179. Copper alloys showed pitting on ASTM B111 grade C71500 (70-30), and denickelification on ASTM B111 grade C70600 (90-10), and is a good alternative material for use apart from carbon steel alloys, recording a low corrosion rate of 0.05 mm/year. The EDS analysis supported the findings showing higher weight percent of iron and sulphur on surface of the alloys after exposure to the SRB media. This implies that the presence of the sulphur ion indeed increased the corrosion rate. ASTM A516-70 carbon steel was chosen as a suitable alternative material to the stainless steel in this environment. The Tafel plot recorded a corrosion rate of 1.08 mm/year for ASTM A516-70 when exposed to SRB media.