Muhammad Zaimi

Nanocomposite TiAlBN Coatings as a Corrosion Protection Layer for AZ91 Mg Alloy Substrate in NaCl

Magnesium alloys create increasing interest in structural application where weight reduction is vast concern. However, one of magnesium drawback in various applications is low corrosion resistance. In general, a hard coating can be applied on metal to combat such a problem. AlN and TiN coatings are most widely utilized in manufacturing area i.e for structural application due to its high hardness, high chemical stability, and excellent adhesion to substrates. Most recent, TiAlBN coating catch many attentions due to its superior properties than other most studied hard coating. The incorporation of aluminium in the cubic face centered TiN structure on Ti sites leads to deformation and strengthening of the crystal structure of the coating together. Moreover, incorporation of BN in this coating should improve and enhanced the corrosion resistance of Mg alloy. Therefore, in this study, TiAlBN coating have been chosen to be deposited on Mg alloy using reactive magnetron sputtering together with AlN and TiN coatings for comparison study. During depositions, target power, working pressure and bias voltage are optimized for each coating. Analysis on the effect of AlN, TiN and TiAlBN coatings on Mg alloy substrate include thickness measurement and microstructure by scanning electron microscope (SEM). Coatings phase were analysed using glancing angle X-ray diffraction analysis (GAXRD) and corrosion properties were evaluated using potentiodynamic polarization in NaCl solution. TiAlBN shows better performance of corrosion protection with the least corrosion rate (penetration rate = 0.20 mm/yr; mass loss rate=0.97g/m2d) in sodium chloride (NaCl) solution although having the lowest coating thickness (412 nm).

Electrochemical Performance of Multi Walled Carbon Nanotube and Graphene Composite Films Using Electrophoretic Deposition Technique

This study aims to investigate multi-walled carbon nanotube and graphene composite thin films fabricated using cathodic electrophoretic deposition in aqueous solution. The deposition mechanism and films microstructure were investigated using the cyclic voltammetry (CV) and field emission scanning electron microscope. The depositions yield varied by the deposition time and deposition voltage. The composite films were studied for its application in the electrochemical capacitor. The electrochemical performance showed the capacitive behavior of the films in 6 M potassium hydroxide electrolyte. CV scans were verified from 0 to 1 V at different scan rates. The specific capacitance of 29 Fg-1 was achieved at the scan rate of 1 mVs-1.

Effect of electroless Ni-P thickness on EFTECH 64-Ni, EFTECH 64-Cu and C194-Ni bump

Long-term reliability of board level solder joint is significantly affected by the properties of surface finish. Recently, Electroless Nickel Immersion Gold (ENIG) was offered as alternative surface finish with high solder joint strength to reduce cost. However, the use of electroless Ni-P deposition produces intermetallic compound (IMC) that exists between solder Ni-P alloy boundaries after thermal aging process. In this study, the effect of various Ni-P deposit thickness and different substrate on its failure mode is studied by measuring its shear strength and observing shear morphology after thermal aging. The Ni-P alloy deposit thickness is set to 0.5, 2.5 and 4.5 μm. The substrate used EFTECH 64-Ni, EFTECH 64-Cu and C194-Ni bumps. From the results, the use of EFTECH 64-Cu substrate produce fracture failure at both Ni-P - Substrate and Ni-P - IMC compare to other substrates. Aside that, C194-Ni alloy produces consistence shear strength but unable to produce consistence standard deviation. As a conclusion, the EFTECH 64-Ni bump is consider as suitable substrate material due no fracture was observed between the substrate boundaries and the IMC boundaries.

Electroless Ni-Co-Cu-P Alloy Deposition in Alkaline Hypophosphite Based Bath

The use of electroless deposition method to deposit nickel alloy attracts attention due to its uniformity, corrosion resistance in neutral media and low friction. Quaternary nickel alloy deposit can be achieved by adding metal ion additive into the plating bath. Furthermore, the use of alkaline bath can accelerate the deposition rate, and provide sufficient thickness for corrosion protection. In this study, an electroless quaternary nickel alloy is deposited on iron coupons by adding cobalt and copper ions in hypophosphite based Ni-P alkaline bath. The nickel alloy deposit surface morphology is studied using scanning electron microscope (SEM) and x-ray fluorescence (XRF). Corrosion behavior of the nickel alloy is investigated using polarization curve measurement in 3.5wt% NaCl aqueous solution. From the results, the elecroless Ni-Co-Cu-P alloy coating produced at higher plating bah pH is harder than the lower bath pH. Higher Co, Cu and P content in the Ni alloy exhibit broader passive area in the polarization curve measurement results.

Corrosion Performance of Nitrided Based Coating on AZ9I Mg Alloy in Hank’s Solution

The use of Magnesium alloys as bioresorsable metallic implant is interesting to study due to the properties of magnesium ions which can be found naturally in bone tissue as well as are essential to human metabolism. However, its fast degradation rate and excess of these ions in the body may cause undesirable health effects. Therefore, surface treatment such as coating can offer an alternative solution to slow down the fast degradation rate of magnesium alloy. Thus, in this study, attempt has been made to coat the AZ91 magnesium alloy substrate with TiN, AlN and TiAlBN coatings using single hot press target with r.f. magnetron sputtering technique. During deposition, target power, working pressure and bias voltage were optimized for each coating deposition. Coating microstructure and its crystal phases are analysed using SEM and glancing angle X-ray diffraction analysis (GAXRD). Corrosion properties were evaluated using potentiodynamic polarization using Hank’s Solution as a medium to simulate body fluid. Result showed that TiAlBN coating is acting most successfully as a protection layer by slowing down the penetration of corrosion towards AZ91 Mg alloy substrate. SEM micrographs show a minimum damage to the substrate’s surface seen after subjected to corrosion test. In conclusion, TiAlBN coating is able to protect AZ91 Mg alloy substrate surface from corrosion and able to slow down their degradation rate. The better performance of TiAlBN coating create interest to further works on exploring the potential of this hard coated on AZ91 Mg alloy for biomaterial application.

Electrochemical Impedance Behavior of Various Composition Quaternary Ni Alloy in 3.5 Wt% NaCl

Zinc and copper addition into electroless Ni-P alloy matrix produces quaternary Ni alloy that exhibits lower corrosion resistance behavior compared to Ni-P and Ni-Cu-P alloy in 3.5 wt% NaCl solution. The corrosion behavior of the alloy is previously studied using the anodic polarization curve measurement. The results show that the corrosion potential of different alloy composition is almost similar to each other for electroless Ni-Zn-Cu-P alloy. However, the surface resistance of the alloy needs to be confirmed by using electrochemical impedance spectroscopy. The alloy was first deposited on an iron substrate using electroless Ni alloy deposition method approximately similar thickness at different plating bath pH of 8.50 and 9.50. The Ni alloy coated substrate was used as working electrode immersed into a solution of 3.5 wt% NaCl. The electrochemical cell consists of Pt and Ag/AgCl/KCl (saturated) as counter and reference electrode respectively. Electrochemical impedance measurement was done at open circuit potential. The measurement started from 100 kHz to 10 mHz with 10 mV of sinusoidal perturbation applied to the cell. Other types of alloy including Ni-P, Ni-Cu-P and Ni-Zn-P, were compared with Ni-Zn-Cu-P alloy. From the results, the Ni-Zn-Cu-P exhibits the lowest corrosion behavior compared to other Ni alloy due to low charge transfer resistance (Rct) observed small inductive loop at low frequency region of the Nyquist plot. Furthermore, the Nyquist plot for Ni-Zn-Cu-P for pH 8.50 and 9.50 showed comparable result; hence, the effect of pH has less effect on corrosion resistance of the electroless Ni-Zn-Cu-P alloy.

Electrophoretic Deposition and Heat Treatment of Steel-Supported PVDF-Graphite Composite Film

Polymeric poly (vinyliden fluoride) (PVDF) is nontoxic. It possesses a better mechanical flexibility and requires a lower synthesis temperature, as compared to the piezoceramic counterparts. In order to achieve a competitive advantage against the current piezoelectric sensor, graphite could replace a more expensive silver-palladium as the electrodes for the piezoelectric PVDF. This paper reports the preliminary results on the synthesis of steel-supported graphite-PVDF/PVDF/graphite-PVDF composite films using the two-step process, consisted of the electrophoretic deposition (EPD) and heat treatment. The composite films were characterized by means of the optical microscopy, scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The heat treated graphite-PVDF electrode deposited by EPD provides adequate mechanical strength for the subsequent depositions of pure PVDF layer and the second layer of graphite-PVDF composite electrode. However, the final heat treatment stage did not eliminate the fine and large cracks of the composite film, which might be attributed to high residue stresses and weak bonding between graphite and PVDF particles in the post-heat treated composite films. Nevertheless, the increase in final heat treatment temperature of the composite film at Stage 3 improved the graphite and PVDF grain alignment, as well as its crystallinity.

Corrosion Analysis of Carbon Steel Pipeline: Effect of Different Sulfuric Acid Concentrations

Oil and gas industry has been hugely contributing any government income and this industry is highly required to control corrosion failures in pipelines which may potentially cause substantial human and economic losses. The objective of this study is to study the effect of sulfuric acid (H2SO4) electrolyte concentration to corrosion behavior of the internal surface of natural gas pipeline by using Tafel extrapolation method. Surface morphology of the samples is studied using optical microscope and scanning electron microscope to investigate the correlation between the corrosion rate and surface morphology. As results, the corrosion rate increases with higher concentration of H2SO4. Microscopic analyses also confirmed the presence of pitting corrosion, and micrometer thick of corrosion product was developed on the surfaces. The data can be used to managing the pipelines effectively and prevention method can be taken in order to extend the life span of the pipeline.