Papers by Keyword: Galvanic Corrosion

Abstract: In order to evaluate the corrosion fatigue property of dissimilar joint by the simultaneous fatigue-corrosion test, an original compact shear fatigue test machine has been developed and installed in the combined cycle corrosion equipment. The material used were an innovative ultra-high strength steel (i-UHSS) with the ultimate strength of 1.5 GPa & large elongation of 20 % and an innovative Al-Mg alloy with high ductility. The dissimilar lap joints were fabricated by resistance spot welding (RSW) or refill friction stir spot welding (RFSSW). An innovative adhesive was also employed for producing the weld-bonded (WB) joints. An accelerated corrosion condition conducted in this research was the climate of high temperature & high humidity. The natural corrosion fatigue tests were also performed outdoor on Miyakojima Island in Japan and indoor in an air-conditioned room. The accelerated corrosion fatigue tests suggest that the corrosion fatigue property of the dissimilar WB joint joined by RSW seems to be better than that of the WB joint joined by RFSSW because of the difference in the area of adhesive interface. In addition, it is considered that the crack would propagate in the adhesive interface and then lap joint might break suddenly after achieving the crack to the circumference of joint interface produced by RSW or RFSSW. Moreover, it can be concluded that the accelerated corrosion condition employed in the research seems to be an appropriate condition for examining the corrosion fatigue property of lap joint in the climate of high temperature and high humidity.

Abstract: There has been a significant increase in the use of composite materials to reinforce metallic structures. Such an increase has been especially noted in marine and underground applications, where there is a higher corrosion impact. Whilst there have been several attempts to investigate the mechanical properties of several synthesized composite materials, few of these have analyzed the corrosion of such composite materials at different weight ratios. The aim of this paper is to explore the best weight ratios of a graphite/Zinc composite matrix that would yield the lowest corrosion rate for a variety of applications. The research is validated using experimentation based on six additives of graphite (1wt%, 2.5wt%, 4wt%, 6wt%, 8wt%, and 10wt%), which are used as reinforcements for a range of weight ratios. The additives were prepared using the powder metallurgy method. The corrosion rate for all specimens used was carried out at the room temperature of 27 °C. Analysis results showed that 1wt% of graphite additive has the highest corrosion resistance compared to other weight ratios tested. This has been verified by examining the microstructure of the composite using an optical microscope for 12h, 24h, and 48h of immersion time in a 1M HCl acid solution.

Abstract: Granulated iron oxide particles were incompletely reduced to structured particles comprised metallic iron and residual iron oxides. Structured particles were pressed into prismatic compacts and sintered. Some of sintered specimens were subsequently phosphatized and calcined. Specimens with an iron phosphate coating were found stiffer than specimens without coating. In Hanks' solution, a galvanic corrosion was induced by more noble iron oxides coupled to a less noble metallic iron. This could explain higher corrosion potentials and higher rates of iron dissolution in comparison with a pure iron. The coating of specimens with iron phosphates shifted corrosion potentials towards more negative values and slowed down the dissolution of iron. This was most likely caused by a reduction in oxygen flow through the coating to iron-oxide cathodes, which has enhanced the influence of diffusion control on the kinetics of reduction reaction.

Abstract: Chemical Mechanical Planarization (CMP) is a key process for IC manufacturers. Tungsten (W) is an important material for connecting logic elements and for connecting memory elements, thanks to its excellent planarization, filling, mechanical and electromigration properties. W slurries are developed to remove high amounts of W via an abrasive, in conjunction with an oxidizer. After the polishing process, the planarized surface is contaminated with abrasive particles, organic residue, pad debris and metal cations through covalent or hydrogen-bonding, electrostatic and Van der Waals attractions. Post-CMP cleaning is required to remove all these contaminants while exhibiting low galvanic and chemical corrosion. Formulated cleans are needed to meet all these requirements. The performance of formulated W/TiN post-CMP cleaners for N10 and N7 has been evaluated. The newly developed formulations show a factor 4 reduction in metal surface contamination (from ~2 x 10¹² atoms/cm² to ~ 5 x 10¹¹ atoms/cm²), which is important to prevent dielectric breakdown. Very low particulate and organic residue defectivity was additionally confirmed by different surface characterization techniques: XPS, FTIR, contact angle/surface energy.

Abstract: The impact of dissolved oxygen (O₂) on cobalt (Co) corrosion in dilute HF (dHF) solution was studied. It was confirmed that Co etch rate was enhanced as the amount of dissolved O₂ in the HF solution increased. The Co etch rate was also found to increase radially outward when performed on a single-wafer spin process in atmospheric air due to the uptake of O₂ during the dispense process. The galvanic corrosion of Co was investigated with two types of structures with a Co/Cu interface in different dissolved O₂ concentrations, i.e. (1) Co bump structures on Cu and (2) Cu lines with a Co/TaN liner/barrier structure. By controlling both the dissolved and the atmospheric O₂ levels, galvanic corrosion prevention at the Co/Cu interface was achieved.

Abstract: The corrosion behavior of Al-B₄C metal matrix composites in H₃BO₃ solutions with different Cl^- contents was investigated using potentiodynamic polarization and zero resistance ammetry techniques. Results show that the corrosion of Al-B₄C composites in H₃BO₃ solution increases with increasing B₄C volume fraction in the composites. The main corrosion characteristic of Al-B₄C composites in H₃BO₃ solution is the galvanic corrosion between Al matrix and B₄C particles. In the galvanic couple, B₄C particle acts as cathode and Al matrix acts as anode. The cathodic reaction is hydrogen revolution reaction, which controls the corrosion mechanism of Al-B₄C composites. Pitting is not observed on the composite surface in the H₃BO₃ solution with zero Cl^-. However, with addition of Cl^- in H₃BO₃ solution, pitting occurs and the corrosion resistance remarkably decreases with increasing Cl^- content. The corrosion resistance of Al-B₄C composites in H₃BO₃ solutions is compared with that in the standard 3.5% NaCl solution.

Abstract: We discuss several mechanistic approaches and experimental data for improving post-CMP cleaning of W plugs with TiN as barrier liner, and dielectric substrates SiO₂ and Si₃N₄ for use at the 10 nm technology node (metal pitch of 40 nm). Particle charge in the low pH, W CMP slurries are usually positive, and the W surface is always negatively charged at pH >3. Therefore, a strong electrostatic attraction is expected to occur between the W surface and the residual particles during post-CMP cleaning. Two main approaches were chosen to break down the strong particles-W surface post-CMP electrostatic interactions, as well as particles dispersion and prevention of redeposition: (1) using cleaning additives able to adsorb at the W surface and reverse the W surface charge; (2) using organic additives to reverse the particle charge. The latter approach results in two strongly negative charged surfaces, which are able to repulse each other, and leads to the best cleaning.

Abstract: The galvanic corrosion of Cu/Al/Cu clad in 3.5% NaCl brine solution has been studied. No visible intermetallic compounds were found at the Cu/Al interface after roll-bonding, But Intermetallic layer grew up to 40μm after heat treatment 500°C for 10hours. The galvanic corrosion occurred significantly in the Al region in contact with Cu. The depth of the dissolved Al gradually decreased with distance away from the Cu/Al interface. Both IDR width and IDR depth increased steadily with increase of soaking time. The IDR width and depth of as-roll-bonded Cu/Al/Cu is far greater than those of heat-treated Cu/Al/Cu at 500°C for 10hours, suggesting the presence of intermetallic compounds influences the galvanic corrosion behavior.

Abstract: The galvanic corrosion behavior of titanium (TA2)/Cu-Ni alloy (B10)/low alloy steel (921A) multi-material system has been studied using a zero-resistance ammeter (ZRA) in seawater at different temperatures. After the tests, the surface morphologies of the samples were detected by SEM. Results showed galvanic corrosion behavior of TA2/B10/921A fulfill the mixed potential theory, 921A acts as the anode and both TA2 and B10 act as the cathodes. The effect of temperature on the galvanic corrosion is important, the corrosion rate increases with increasing temperature.

Abstract: The galvanic corrosion behavior of 70-30 copper-nickel alloy as a brand new seawater pipe material and nickel-aluminum bronze as the commonly used pipe valve material in simulated low temperature conditions of deep sea was studied. The galvanic corrosion potential and galvanic current density of the pair were monitored, and the galvanic corrosion tendency and effect at different temperature were evaluated. Combined with the electrochemical measurements, the influence of seawater temperature on galvanic corrosion behavior was also discussed. The results showed that as the result of coupling, 70-30 copper-nickel alloy acting as the coupled cathode was prevented from corrosion, while nickel-aluminum bronze became the sacrificial anode. With the decrease of seawater temperature, the galvanic corrosion tendency and galvanic corrosion rate of the pair decreased. The change in galvanic corrosion tendency with seawater temperature was attributed to the different electrochemical properties induced by the inherent difference in chemical compositions of the alloys. The low galvanic corrosion rate and effect were related to the reduced mass transfer rates at low temperature. Moreover, the electrochemical behavior of the copper alloys was much sensitive to the change in the amount of dissolved oxygen at the lower seawater temperature, especially for the alloy with higher passivation ability, i.e., 70-30 copper-nickel alloy.