Quantum Chemical Study on the Corrosion Inhibition of Copper Using Some Thiosemicarbazides and Tetrazoles

Relationships between corrosion inhibition efficiency of two thiosemicarbazide based compounds namely; 4-phenyl thiosemicarbazide (PTSC), Salicylaldehyde thiosemicarbazone (STSC) and 4 tetrazole derivative; 5-Mercapto-1-methyltetrazole (MMTA), 5-(3-Pyridyl)-1H-tetrazole (PyTA), 5-Amino-tetrazole mono hydrate (ATA) and 5-phenyl tetrazole (PTA) and their molecular electronic properties have been theoretically studied at the level .............(More details are available in the full paper) Keywords: Thiosemicarbazides and Tetrazoles, structural parameters DOI: 10.7176/CMR/11-2-04

Spot Joining of Si3N4 and SIC Ceramics using Selective Area Laser Deposition (SALD) Technique

Mechanical Engineerin

Electroless Plating of Ni-B Composite Coating on AZ31 Mg alloy

A Ni–B coating was electroless-deposited directly on H3PO4/HF pickled AZ31. The thickness of the plating layer was estimated through weight gain measurements and was affected by temperature, time and bath composition. The highest thickness was obtained at 6 g/L of NaHB4 at 85oC.  An adherent compact layer of Ni-B was obtained. Electrochemical impedance spectroscopy measurements in 3.5 wt.% sodium chloride aqueous solution suggest that the plating can protect the magnesium alloy substrate from corrosion attack

Corrosion Inhibition of Copper in Sea Water Using Derivatives of Thiosemicarbazides

Three corrosion inhibitors namely: 4-allyl-3-thiosemicarbazide C4H9N3 S, 4-(1-methyl)-3-thiosemicarbazide,4-tolyl-3-thiosemicarbazide were tested as corrosion inhibitors for copper in sea water environmnt.Copper samples were tested using potentiodynamic polarization technique in the absence and in the presence of corrosion inhibitors.   High inhibition efficiencies (≥95%) were shown by the tested inhibitors.  The best performance was shown by 4-tolyl-3-TSC

Effect of Pickling and Activation Treatments on the Performance of Electroless Plating of Ni-B Coating on AZ31 Mg Alloy

Pickling is particularly critical before Ni-B electroless plating to create a uniform and catalytically active surface.  In the present work, pickling treatment of AZ31 Mg alloy was performed in phosphoric acid followed by immersion in 40% HF.  The effect of concentration of both H3PO4 and HF as well as the effect of time were investigated.   The pickled samples were then electroless plated with a Ni-B composite.  The performance of the Ni-B composite coating was investigated under the SEM.Results show that the highest quality coating was obtained upon pickling AZ31 Mg alloy samples in 50% phosphoric acid for 1 min, followed by activation in 40% HF for 15 min. Higher concentration of H3PO4 results in a higher concentration of PO3−4, leading to a higher tendency to produce insoluble films (mainly Mg3(PO4)2 and AlPO4) on the substrate surface slowing down the rate of Mg alloy oxidization and dissolution.  Activation of pickled AZ31 Mg samples in HF results in the formation of corrosion resistant dense layer of magnesium fluoride. SEM investigation predicted the electroless deposition of an adherent compact layer of Ni–B composite coating on the H3PO4/HF pickled AZ31 samples. Key Words: AZ31 Mg alloy, pickling, activation, HF, electroless plating DOI: 10.7176/CMR/11-5-04 Publication date:May 31st 201

Effect of Al2O3 and WO3 Ceramic Additives on the Surface Morphology and Mechanical Properties of Electroless Nickel-Boron Composite Coatings Fabricated on AZ31 Magnesium Alloy

In the present study, synthesis and a comparison of properties (structural and mechanical)  of  Ni–B and Ni–B–Al2O3 and Ni-B-WO3 composite coatings have been presented  to  elucidate the beneficial role  of Al2O3 or WO3 addition in  binary Ni–B coatings. The  Ni–B– Al2O3 and Ni-B-WO3 coatings were synthesized by  adding Al2O3 or NaWO3 powdered particles into the  above  mentioned Ni–B  coating solution.  A significant improvement in mechanical properties has been observed by the addition of Al2O3 or WO3 additions.  This novel composite coating composition will be useful for wear and corrosion applications. DOI: 10.7176/CMR/11-8-05 Publication date:October 31st 201

Enhancement of Physical Properties and Corrosion Resistance of Al-Cu-Al2O3/Graphene Nanocomposites by Powder Metallurgy Technique

In this study, we enhanced the adhesion of graphene nanosheets to achieve homogeneous dispersion, consequently improving the electrical and thermal conductivity, coefficient of thermal expansion, and corrosion resistance with an aluminum matrix containing up to 1.5 wt. % graphene. First, 2.5 wt. % Al2O3 and varying ratios of graphene up to 1.5 wt. % were coated with 5 wt. % silver nanoparticles to metalize their surfaces. Predetermined portions of coated alumina and graphene were mixed with Al/10 wt. % Cu powder for 45 h. Mixed samples were compacted under 600 MPa and sintered at 565 °C in a vacuum furnace for 60 min with a low heating rate of 2 °C/min. The strengthening effect of the added materials on the density, microstructure, electrical and thermal conductivities, thermal expansion, and corrosion behavior of aluminum were investigated. Excellent adhesion and homogeneous dispersion of the investigated reinforcements were achieved. Three phenomena were observed: (1) an improvement in the densification, electrical and thermal conductivity, thermal expansion, and corrosion rate by adding 10 wt. % Cu to the aluminum matrix; (2) deterioration of the properties of Al/10 wt. % Cu with the addition of 2.5 wt. % alumina nanoparticles; and (3) improved properties with the addition of graphene nanosheets up to 1 wt. % and a decrease in property values beyond 1.5 wt. % graphene content due to the formation of agglomerations and pores in the metal matrix