İsmail Hakkı Karahan

A study on electrodeposited Zn–Co alloys

In this study, the corrosion properties of Zn–Co alloys prepared by the electrodeposition method from a sulfate bath under potentiostatic conditions on steel and aluminum substrates have been investigated. The deposit morphology and elemental composition were examined by scanning electron microscopy (SEM)/EDX. The preferred crystallographic orientations of the deposits have been determined by the x-ray diffraction (XRD) technique. The effects of bath composition on the phase structure, morphology and corrosion behaviors have been studied. It has been observed that the cobalt content strongly affects the structure and corrosion stability of Zn–Co alloys. It was found that amorphous alloys were obtained with high Co contents, while crystalline alloys were formed with high Zn contents.

The effect of repeated porcelain firings on corrosion resistance of different dental alloys

PURPOSE The aim of this study was to evaluate the effects of repeated porcelain firing process on the corrosion rates of the dental alloys. MATERIALS AND METHODS Cr-Co, Cr-Ni and Pd-Ag alloys were used for this study. Each metal supported porcelain consisted of 30 specimens of 10 for 7, 9 and 11 firing each. Disc-shaped specimens 10 mm diameter and 3 mm thickness were formed by melting alloys with a propane-oxygen flame and casted with a centrifuge casting machine and then with the porcelain veneer fired onto the metal alloys. Corrosion tests were performed in quintuplicate for each alloy (after repeated porcelain firing) in Fusayama artificial saliva solution (pH = 5) in a low thermal-expansion borosilicate glass cell. Tamhane and Sheffe test was used to compare corrosion differences in the results after repeated firings and among 7, 9 and 11 firing for each alloy. The probability level for statistical significance was set at α=0.05. RESULTS The corrosion resistance was higher (30 mV), in case of 7 times firing (Commercial). On the other hand, it was lower in case of 11 times firing (5 mV) (P<.05). CONCLUSION Repeated firings decreased corrosion resistance of Pd-Ag, Cr-Co and Cr-Ni alloys. The Pd-Ag alloy exhibited little corrosion in in vitro tests. The Cr-Ni alloy exhibited higher corrosion resistance than Cr-Co alloys in in vitro tests.

Investigation of effect of the bath components on coating properties in electrodeposition of Ni, Ni-B and Ni-B/hBN coatings

In this study, pure nickel, Ni-B alloy and Ni-B/hBN composite coatings were produced by electrodeposition. To obtain these coatings, the amounts of the components added to the bath were kept constant and the effects of bath components on the coatings were investigated separately. Electrochemical behaviors, crystal structures, surface morphologies and chemical composition of films analysed with cyclic coltametry (CV), XRD, SEM and EDS, respectively. Additionally corrosion resistance of the coatings was evaluated by open circuit potential and Tafel extrapolation methods in %3,5 w.t. NaCl solution. The results obtained in this study indicate that smooth, compact and fine grained coatings were produced. The components added to the electrolyte were affect crystal structure, corrosion resistance and other properties seriously.Bu calismada, saf nikel, Ni-B alasim ve Ni-B/hBN kompozit kaplamalar elektrodepolama yoluyla uretilmistir. Bu kaplamalari elde etmek icin banyoya eklenen bilesenlerin miktarlari sabit tutulmus ve her birinin ayri ayri kaplama uzerine etkileri arastirilmistir. Uretilen kaplamalarin kristal yapilari XRD ile, yuzey morfolojileri ve kimyasal icerik analizleri SEM ve EDS ile, elektrokimyasal davranislari ise donusumlu voltametri (CV) ile incelenmistir. Ayrica kaplamalarin korozyon dayanimlari % 3.5 NaCl iceren cozelti icerisinde acik devre potansiyeli ve Tafel ekstrapolasyon metotlariyla belirlenmistir. Elde edilen sonuclara gore ince taneli, duzgun yuzeyli ve kompakt kaplamalar uretilmistir. Banyoya eklenen bilesenler kristal yapiyi, korozyon dayanimini ve diger ozellikleri ciddi derecede etkilemektedir.