Chromium implantation

Fig. 31. Potentiokinetic polarization curves for chromium-implanted (5 X 10 Cr ions/cm ), in comparison with unimplanted iron (after )...

It is naturally interesting to compare the corrosion behavior of chromium-implanted iron with conventional Fe-Cr alloys. 

Implantation and analysis were performed on two specimens during the first part of this report period (1) oxygen implanted into a chromium layer on sapphire, and (2) chromium implanted into a Ti.Oy/AlgOg multilayered structure on silicon. 

Vilarigues M, Fernandes JCS, Alves LC, da Silva RC, (2008), Electrochemical behaviour of chromium-implanted magnesium in hydroxide, chloride and sulphate solutions . Surface and Coatings Technology, 202, 4086-4093. 

Over time a large variety of materials have been used, including ivory, stainless steel, chromium—cobalt, and ceramics for the acetabular component. None proved sufficient. The implant material composition must provide a smooth surface for joint articulation, withstand hip joint stresses from normal loads, and the substance must disperse stress evenly to the cement and surrounding bone. 

Cobalt—Chromium Alloys. Co—Cr and Ni—Cr alloys are used predominately for the casting of removable partial dentures fixed partial dentures (bridges), crowns, and inlays are also cast. Because of high hardness, corrosion resistance, and wear resistance cobalt-chromium alloys are used for bite adjustments and as serrated inserts in plastic teeth used in fliU dentures. These alloys are well tolerated by the body and also are used for dental implants and orthopedic implant alloys. 

Stenberg, T. and Bergman, B. Release and Uptake of Cobalt from Cobalt-Chromium Alloy Implants , Acta Odontologia Scandanavia 41, 149-154 (1983)... 

Edwards e/a/. carried out controlled potential, slow strain-rate tests on Zimaloy (a cobalt-chromium-molybdenum implant alloy) in Ringer s solution at 37°C and showed that hydrogen absorption may degrade the mechanical properties of the alloy. Potentials were controlled so that the tensile sample was either cathodic or anodic with respect to the metal s free corrosion potential. Hydrogen was generated on the sample surface when the specimen was cathodic, and dissolution of the sample was encouraged when the sample was anodic. The results of these controlled potential tests showed no susceptibility of this alloy to SCC at anodic potentials. 

The successful clinical use of titanium and cobalt-chromium alloy combinations has been reported Lucas etal. also investigated this combination using electrochemical studies based on mixed potential and protection potential theories. Verification of these studies was made by direct coupling experiments. The electrochemical studies predicted coupled corrosion potentials of -0.22 V and low coupled corrosion rates of 0.02 ft A/cm. Direct coupling experiments verified these results. The cobalt-titanium interfaces on the implants were macroscopically examined and no instances of extensive corrosion were found. Overall, the in-vitro corrosion studies and the examination of retrieved prostheses predicted no exaggerated in-vivo corrosion due to the coupling of these cobalt and titanium alloys. 

Edwards, B. J., Louthan, M. R. and Sisson, R. D., Hydrogen Embrittlement of Zimaloy A Cobalt-Chromium-Molybdenum Orthopaedic Implant Alloy , in Corrosion and Degradation of Implant Materials, Second Symposium, (Eds) A. C. Fraker and C. D. Griffin, 11-29 ASTM Publication STP 859, Philadelphia (1985)... 

Applications Ion implantation is widely employed to improve the life of tools. Thus press tools, dies and gear cutters can be treated to increase their durability by three times or more. Nitrogen-implanted tungsten carbide drawing dies for copper and iron wire can be improved up to fivefold. By implanting chromium, aluminium or silicon a considerable increase in the corrosion resistance of steel can be obtained. Implantation of chromium into aircraft bearing alloys has improved their durability in marine environments . 

Zeh A et al (2007) Release of cobalt and chromium ions into the serum following implantation of the metal-on-metal Maverick-type artificial lumbar disc (Medtronic Sofamor Danek). Spine 32(3) 348-352... 

Chromite ore roast mixed with sheep fat implanted intrapleurally in rats produced sarcomas coexisting with squamous cell carcinomas of the lungs the same material implanted in the thigh of rats produced fibrosarcomas/ However, the lARC concluded that these studies were inadequate to fully evaluate the carcinogenicity of this compound/ Other animal studies have found no increase in the incidence of tumors with chromium metal and chromite ore/ The lARC has determined that there is inadequate evidence in humans and animals for the carcinogenicity of metallic chromium and chromium(III) compounds. 

Chromic acetate (see Chromium and chromium compounds) Chromic chloride (see Chromium and chromium compounds) Chromic oxide see Chromium and chromium compounds) Chromic phosphate see Chromium and ehromium compounds) Chromite ore see Chromium and ehromium compounds) Chromium and chromium compounds see also Implants, surgical)... 

Cobalt[III] acetate (see Cobalt and eobalt compounds) Cobalt-aluminium-chromium spinel (see Cobalt and cobalt compounds) Cobalt and cobalt compounds (see also Implants, surgical)... 

An accurate determination of copper and zinc traces in human serum samples from the International Measurement Evaluation Programme-17 launched by IRMM (Geel) has been made by isotope dilution TIMS.38 An analytical method for the multi-element determination of metals (Ti, V, Cr, Co, Ni and Mo) potentially released from dental implants and prostheses into human body fluids (in blood and urine) by ICP-MS (double-focusing sector field instrument and quadrupole instrument with octopole collision cell) for medical studies was developed in Sanz-Medel s group.39 The Cr and Co concentrations found in blood samples of patients with chromium-cobalt based alloy varied in the sub-p,gl 1 range and were not significantly higher than the basal levels found by other authors.40... 

The elements of groups 3 through 12 are all metals that do not form alkaline solutions with water. These metals tend to be harder than the alkali metals and less reactive with water hence they are used for structural purposes. Collectively they are known as the transition metals, a name that denotes their central position in the periodic table. The transition metals include some of the most familiar and important elements—iron, Fe copper, Cu nickel, Ni chromium, Cr silver, Ag and gold, Au. They also include many lesser-known elements that are nonetheless important in modern technology. Persons with hip implants appreciate the transition metals titanium (Ti), molybdenum (Mo), and manganese (Mn), because these noncorrosive metals are used in implant devices. 

The production of corrosion-resistant materials hy alloying is well established, hut the mechanisms are noi lull) understood. It is known, of course, that elements like chromium, mckcl. titanium, and aluminum depend for their corrosion resistance upon a tenacious surface oxide layer (passive film). Alloying elements added for the purpose of passivation must be in solid solution. The potential of ion implantation is promising because restrictions deriving from equilibrium phase diagrams frequently do not applv li e., concentrations of elements beyond tile limits of equilibrium solid solubility might he incorporated). This can lead to heretofore unknown alloyed surfact-s which are very corrosion resistant... 

Compared to the corresponding carbides the heats of oxygen chemisorption on metals are higher. For example, on metallic tungsten the heat of adsorption is 812 kJ/mole 02, while on metallic chromium it is 730 kJ/ mole 02n. These values are significantly higher that those of the carbides of the same metals (Table 16.2). Thus, carbon atoms, when implanted in the metal lattice, reduce the adsorption affinity of the metal atoms towards oxygen. 

A decrease in fertility (decreased number of implantations and viable fetuses) was observed in male and female mice that were exposed to 6 mg chromium(VI)/kg/day as potassium dichromate for 12 weeks and then were mated with unexposed males and females (Elbetieha and Al-Hamood 1997). An increase in the number of mice with resorptions was also observed in the exposed females. 

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