Potentiodynamic Polarization Aspects of the As-cast and Sprayed Al-Si, Al-Sn and Al-Sn-Si Alloys in a Sodium Chloride Solution

2010 ◽  
Vol 19 (9) ◽  
pp. 1357-1361 ◽  
Author(s):  
M. Anil ◽  
S. Balaji ◽  
A. Upadhyaya ◽  
M. K. Ghosh ◽  
S. N. Ojha
2008 ◽  
Vol 373-374 ◽  
pp. 240-243 ◽  
Author(s):  
Long Hao ◽  
Ye Ming Zhang ◽  
Chao Yang ◽  
Hua Zhu ◽  
Xu Hui Mao ◽  
...  

With suitable pretreatment, a compact and even nickel-phosphorus alloy coating was obtained on W-Cu alloy by electroless deposition from solutions containing nickel sulphate as a source of nickel and sodium hypophosphite as the reducing agent and a source of phosphorus. The Ni-P coating was normally prepared from acidic baths at high temperature of the order of 90oC with the pH of 4.8 and it was smooth and uniform and exhibited high crystal refinement and high microhardness and superior corrosion resistance. The microhardness, adhesion and corrosion resistance mechanism of Ni-P deposit were studied. The microhardness of the Ni-P alloy deposit increases greatly by tempering at various temperatures. The Ni-P deposit has a strong adhesive force with W-Cu alloy substrate checked by thermal shock test and scribe test. The anti-corrosion ability of Ni-P coating and its anti-corrosion mechanism were measured using immersion experiment and potentiodynamic polarization techniques. The results showed that the corrosion resistance of Ni-P coating was higher than that of W-Cu alloy substrate in the 10vol.% sulfuric acid, monitoring sweat solution and 3.5wt.% sodium chloride solution. The anti-corrosion mechanism of electroless Ni-P coating immersed in 3.5wt.% sodium chloride solution was studied using potentiodynamic polarization techniques. The surface micromorphological morphology and structure of the Ni-P coating were investigated using Scanning Electronic Microscope (SEM) and X-ray Diffraction (XRD). The results indicated that the Ni-P alloy coating consisted of microcrystals and it was amorphous in structure, and the electrochemical measurement showed passive film formed on Ni-P coating during immersion test in the 3.5wt.% sodium chloride solution.


2018 ◽  
Vol 149 ◽  
pp. 01050
Author(s):  
Mohammed Hassoune ◽  
Abdelillah Bezzar ◽  
Latéfa Sail ◽  
Fouad Ghomari

The inhibition of carbon steel corrosion in neutral sodium chloride solution by N,N'- Dimethylaminoethanol (DMEA), at different temperatures, was investigated using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results obtained confirm that DMEA is a good organic corrosion inhibitor for carbon steel in 0.5M of NaCl (concentration encountered in the Mediterranean seawater), over the whole range of temperatures studied. The inhibition efficiency (IE%) increases with increasing DMEA concentration; it reaches highest value for a concentration around 0.125 mol.L-1. Potentiodynamic polarization data show that, the compound studied in this research predominantly act as anodic-type inhibitor. The EIS study reveals that the addition of DMEA decreases the corrosion rate of carbon steel in neutral sodium chloride solution, due to the fact that the inhibitor molecules are strongly adsorbed on the active sites following Langmuir isotherm, thus leading to the formation of a stable protective film on the steel surface which is able to keep the metal/solution interface in a passive state. Furthermore, the values of the activation parameters, i.e. ΔHa and Ea obtained in this study indicate that the adsorption process of DMEA is endothermic and could be mainly attributed to chemisorption, respectively.


2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Vahid Pourzarghan ◽  
Bahman Fazeli-Nasab

AbstractThe most important inhibitors used in bronze disease are BTA and AMT. While these inhibitors control corrosion, they are toxic and cancerous. In this study, the acacia fruit extract (200 ppm to 1800 ppm) was used to the prevention of corrosion inhibition of bronze alloy in corrosive sodium chloride solution 0.5 M, for 4 weeks consecutively. The Bronze alloy used in this research, was made based on the same percentage as the ancient alloys (Cu-10Sn). IE% was used to obtain the inhibitory efficiency percentage and Rp can be calculated from the resistance of polarization. SEM–EDX was used to evaluate the surfaces of alloy as well as inhibitory. The experiment was conducted in split plot design in time based on the RCD in four replications. ANOVA was performed and comparison of means square using Duncan's multiple range test at one percent probability level. The highest rate of corrosion inhibition (93.5%) was obtained at a concentration of 1800 ppm with an increase in the concentration of the extract, corrosion inhibition also increased, i.e., more bronze was prevented from burning. Also, the highest corrosion inhibitory activity of Acacia extract (79.66) was in the second week and with increasing duration, this effect has decreased. EDX analysis of the control sample matrix showed that the amount of chlorine was 8.47%wt, while in the presence of corrosive sodium chloride solution, after 4 weeks, the amount of chlorine detected was 3.20%wt. According to the morphology (needle and rhombus) of these corrosion products based on the SEM images, it can be said, they are the type of atacamite and paratacamite. They have caused bronze disease in historical bronze works. The green inhibitor of Acacia fruit aqueous extract can play an effective role in inhibiting corrosion of bronze, but at higher concentrations, it became fungal, which can reduce the role of Acacia fruit aqueous extract and even ineffective. To get better performance of green inhibitors, more tests need to be done to improve and optimize.


1960 ◽  
Vol 38 (9) ◽  
pp. 1488-1494 ◽  
Author(s):  
E. J. Bounsall ◽  
W. A. E. McBryde

An analytical method is described for the determination of microgram amounts of silver in galena ores, based on the "reversion" of silver dithizonate. Silver is separated from relatively large amounts of lead by extraction as dithizonate into chloroform from an aqueous 1:99 nitric acid solution. Separation from mercury, which is also extracted under these conditions and would, if present, interfere in the analysis, is achieved by reverting the dithizonate solution with a 5% aqueous sodium chloride solution which is also 0.015 molar in hydrochloric acid. Following dilution of this aqueous solution and adjustment of pH, silver is again extracted into chloroform as the dithizonate, and determined absorptiometrically. Analyses of a number of galena ore samples showed a precision of within 3% for a silver content ranging from 0.03 to 0.4%.Some other methods for isolating silver from these samples, which were tried but found unsatisfactory, are discussed.


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