M. Karaminezhaad, A.H. Jafari, A. Sarrafi and Gh. Safi
To evaluate bismuth, which is inexpensive and non‐toxic, as a substitute for mercury, indium and gallium in Al‐5%Zn‐X sacrificial anode.
Abstract
Purpose
To evaluate bismuth, which is inexpensive and non‐toxic, as a substitute for mercury, indium and gallium in Al‐5%Zn‐X sacrificial anode.
Design/methodology/approach
The effect of bismuth on the electrochemical behavior of Al‐5%Zn‐Bi in the artificial sea water environment was investigated. Potentiodynamic, potentiostatic, galvanostatic, weight loss and efficiency test methods were employed. The surface of the specimens were studied by SEM and analyzed by EDAX. Image analyzer was also used.
Findings
Adding 0.3‐0.5%Bi to Al‐5%Zn alloy produces considerable active sites on the anode surface and, when the corrosion process continues, the corrosion will be uniform by joining these numerous shallow pits and a high efficiency sacrificial anode will emerge.
Research limitations/implications
Preventing segregation by good casting practice or homogenization heat treatment will be helpful to prevent unpredicted localized corrosion and investigating the effect of these processes on the performance of this new alloy is helpful. Investigating the performance of this new suggested alloy in environments like soil is highly recommended.
Practical implications
Owing to the toxicity of mercury and high price of gallium and indium, bismuth, which has a much lower price and showed a good performance in the present laboratory tests, can be a good substitute for the above mentioned elements.
Originality/value
The previous lack of a systematic research on the effect of bismuth which can be a good substitute for indium and gallium, on anodic behavior of aluminum gives this paper its high value.
Details
Keywords
Yasin Ozgurluk, Kadir Mert Doleker and Abdullah Cahit Karaoglanli
Thermal barrier coatings (TBCs), which are used in high temperature applications of gas turbines, are damaged due to fuels and airborne minerals under working conditions. Stable…
Abstract
Purpose
Thermal barrier coatings (TBCs), which are used in high temperature applications of gas turbines, are damaged due to fuels and airborne minerals under working conditions. Stable zirconia coatings, which are usually used as topcoat materials in TBCs, are damaged by interacting at high temperatures with elements such as vanadium and sulfur from low quality fuels. The purpose of this paper is to see the failure mechanism of TBC systems after hot corrosion damages.
Design/methodology/approach
CoNiCrAlY metallic bond coatings of TBC samples were produced by cold gas dynamic spray method which is a new trend production method and stabilized zirconia ceramic top coating was produced by atmospheric plasma spray method. In total, 50% by weight of V2O5 and 50% Na2SO4 salt mixtures were placed on TBC samples and subjected to hot corrosion test at 1000°C.
Findings
Hot corrosion behaviors of TBC samples were examined by scanning electron microscopy, elemental mapping analysis, energy dispersive X-ray spectrometry analysis and X-ray diffraction analysis. TBC samples were damaged at the end of 12-h cycles.
Originality/value
The paper provides to understand the mechanism of hot corrosion of TBCs with cold sprayed metallic bond coat.