ICMCTF2014 Session D2-1: Coatings for Bio-corrosion, Tribo-corrosion and Bio-tribology

Tuesday, April 29, 2014 8:20 AM in Room Sunrise

Tuesday Morning

Time Period TuM Sessions | Abstract Timeline | Topic D Sessions | Time Periods | Topics | ICMCTF2014 Schedule

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8:20 AM D2-1-2 Properties of Waterborne Polyurethane/Graphene Coatings
MohammadMizanur Rahman, Qasim Habib (King Fahd University of Petroleum and Minerals, Saudi Arabia)

Recently graphene appears to be an inexpensive material available in large quantities with a well-known potential effectiveness for improving mechanical, electrical, thermal and other properties; which make it promising in many applications such as solar cells, hydrogen storage, sensors, batteries, super-capacitors and nanocomposites. Graphene is well dispersed in polymer matrix by solution mixing, melt mixing, and in situ polymerization methods. The ability of graphene to form chemical bonds in polyurethane (PU) chains, it can be effective nanofiller for the PU matrix. Moreover, due to the disk-like shape of the graphene, it is believed that graphene can be choice for improving the gas-barrier property of the nanocomposite protective coating. Waterborne polyurethane (WBPU) consists of mainly urethane and urea groups. Water is the main solvent during synthesis of WBPU. Only water evolved from WBPU at drying stage of coatings. Thus this process is environmentally friendly and free from pollution. In this report we synthesized environmentally friendly WBPU/graphene dispersions through a pre-polymer process using different graphene content (up to 3 wt%). The synthesized dispersions were used as a coating material on mild steel and evaluate the corrosion efficiency of WBPU/graphene coatings.

8:40 AM D2-1-3 Corrosion and Tribological Film of CoCrMo Metal-on-Metal Hip Replacement
Yifeng Liao, Pooja Panigraphi (Northwestern University, US); Mathew Mathew, Robin Pourzal, Alfons Fischer, Markus Wimmer (Rush University Medical Center, US); Laurence Marks (Northwestern University, US)

Metal-on-metal hip replacements have experienced a sharp decline in the last two years due to biocompatibility issues related to wear and corrosion products. Despite some excellent clinical results, the release of wear and corrosion debris and the adverse response of local tissues have been of great concern. There are many unknowns regarding how CoCrMo metal bearings interact with the human body. In this study we investigated the corrosion of CoCrMo alloys with different heat treatments. Solution annealing the wrought alloys resulted in significant grain growth. After annealing at 1230 oC, the second phase, i.e. chromium carbide, was partially dissolved into the matrix. The corrosion current density (icorr) dropped from ~1400 nA/cm2 for the original wrought alloy to ~300 nA/cm2 for solution annealed specimens, indicating that grain coarsening improves corrosion resistance. Pitting corrosion preferentially attacked high-angle grain boundaries with higher energy. All low-angle boundaries were immune to corrosion in the tests. We also evaluated metal-on-metal hip replacement retrieved at revision surgery using electron microscopy and Raman spectroscopy. Thin layers of films are frequently generated in-vivo on CoCrMo MoM surfaces, which are known as tribological films or tribofilms. The EELS results show that tribofilm consist of over 82% sp2-bonded carbon while no discernible nitrogen was found, suggesting that the tribofilm is primarily graphitic carbon. High-resolution TEM micrographs showed short-range ordered fringes in the tribofilm. The results were further confirmed by the Raman spectrum. The tribofilm may be protective against the degradative processes taking place in-vivo in the host body. The composition and ultrastructure is unique and can provide insights into the basic mechanisms of tribocorrosion in metal on metal bearings.

9:20 AM D2-1-5 Electrochemical and Tribocorrosion Aspects of Mixed Metal Contacts in Hip Prostheses
Dmitry Royhman, Maria Runa, Markus Wimmer, Joshua Jacobs, Nadeem Hallab, Mathew Mathew (Rush University Medical Center, US)

Modern hip prostheses feature a modular implant design with a tapered junction between the femoral neck and head, which gives the surgeon flexibility in implant assembly and reduces inventory. Despite their apparent benefits, modular junctions also introduce complications in the hip implant system by introducing additional interfaces. The implant is subjected to various loads and body movements, which may produce micromotion movement at the interface. This can lead to mechanically assisted corrosion (Fretting-Corrosion) and increased release of wear debris and metal ions. This study has two objectives. (1) To study the electrochemical behaviour of commonly used metal alloys (Ti6Al4V and CoCrMo) in a simulated joint fluid evironment with two different pHs (7.6 and pH 3.0), and (2) to implement a new fretting-corrosion apparatus in order to study the fretting-corrosion behavior of Ti-CoCrMo couple in a proteinous solution (BCS) and a saline solution (0.9% NaCl).

For corrosion tests, six Ti6Al4V discs (Mac-Master Carr, Elmhurst, IL) and six wrought high-carbon CoCrMo discs (ATI Allvac, Pittsburgh, PA) were milled from rods. The samples were divided into 4 groups (n=3) as a function of disc type (Ti6Al4V or CoCrMo) and pH level (3.0 and 7.6). For tribocorrosion tests, Ti6Al4V alloy rods (exposed surfaces: 11mm by 11mm) and 2 CoCrMo pins (exposed Surfaces: 12mm diameter x 7 mm thickness) were used. A sinusoidal fretting motion (amplitude of +150 um) was applied to the Ti alloy rod, which was generated through an Instron 8800 load frame (Canton, MA). A load of 200N was applied axially from both sides and the tangential load was monitored. The evolution of potential was monitored during test.

Significant differences were noted within both metals for Ecorr and Icorr (p<0.05; ANOVA). Ti6Al4V exhibited significantly lower Icorr values than CoCrMo in all pHs (p<0.0001; t-test). The Ecorr value for Ti6Al4V was significantly higher than CoCrMo at pH 3.0 (p=0.004; t-test). During the fretting motion, the potential suddenly decreased (0.15V BCS and 0.2V-NaCl) and then slowly recovered during the final stabilization period. Fluctuations of the potentials were evident in both solutions. Further studies will be done by simulating other conditions at the modular junction (pH decrease, varying protein concentrations) to understand the mechanisms driven by the synergistic interaction of wear and corrosion at the modular junction.

9:40 AM D2-1-6 Hydrothermal Deposition of Bio-resorbable Calcium-Phosphate Coating on AZ31 Magnesium for Implant Application
Sara Kaabi Falahieh Asl (Nanyang Technological University, School of Mechanical & Aerospace Engineering, Singapore Institute of ManufacturingTechnology, Singapore); Nemeth Sandor (Singapore Institute of Manufacturing Technology, Singapore); MingJen Tan (Nanyang Technological University , School of Mechanical & Aerospace Engineering,, Singapore)

Interest in biodegradable magnesium (Mg) implants has increased dramatically in the last decade due to their desirable mechanical properties that are close to the human bone, thus avoiding stress shielding effect. In addition, Mg is resorbed in the body and surgery to remove the implant after healing is not needed. However, the high corrosion rate of magnesium and its alloys severely limit their practical applications as implants. To control the corrosion rate of magnesium, biocompatible and bio-resorbable calcium-phosphate (Ca-P) coatings were deposited in this study using AZ31 magnesium substrate and hydrothermal deposition process. Coatings obtained at various temperatures were found to mainly consist of a mixture of monetite [CaHPO4] and tricalcium phosphate [Ca2.86 Mg0.14 (PO4)2] with partially magnesium substituted in tricalcium phosphate structure as determined by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy methods. Coating morphology was examined with scanning electron microscopy (SEM) and the results showed that coatings became denser with increasing temperature. Coating adhesion was examined by pull-out adhesion test indicating only coating cohesive failure at 5.2-5.8 Mpa. It was clearly observed that significant portion of the coating still remained on the substrate after adhesion test. Potentiodynamic polarization conducted in simulated body fluid (SBF) solution confirmed that coating significantly enhanced the corrosion performance of Mg substrate. The corrosion current density of Mg substrate decreased approximately 10,000-fold in the presence of coating. The mass loss for the coated samples was only around 1/3 of that observed for bare substrate, and the amount of Mg ions released from the coated samples was significantly lower than in case of bare substrate after immersion in SBF solution. The described hydrothermal method provided crystalline and compact coatings with excellent adhesion strength and significantly improved corrosion resistance with good prospects for biomedical application.

Keywords: Magnesium, Calcium-Phosphate coating, Corrosion resistance

10:00 AM D2-1-7 Layers of Nanocrystallines and Tribofilm on Artificial Hip Implants Surfaces Induced by Bio-tribo-corrosion Processes
Yu Yan (Key Laboratory for Environmental Fracture (MOE), University of Science and Technology Beijing, China)
Performance and longevity of artificial joints are highly correlated with the surface properties of the prosthesis materials. In view of the importance of this research area, this article consolidates the research work with some fundamental aspects to build up a comprehensive picture of the current state of knowledge. Tribofilm containing organometallic compounds can form on the surface of artificial joints through bio-tribocorrosion processes. Tribofilm can act as a barrier to prevent further ions release and can also act as a solid lubricant. Some test methods are presented, being applied both and . A review of recent work in this area is provided, focusing on the constitution and microstructure of the artificial joints surface.
10:40 AM D2-1-9 Fretting Corrosion of Co-Cr-Mo Alloy with Ti: Specific Tribocorrosive Behavior and Benefits in Comparison with Usual Metallic Alloys Dedicated to Orthopedic Implants
Shintaro Nakahara (Department of Material Processing, Japan); Aleksandra Towarek (Warsaw University of Technology, Poland); Kyosuke Ueda (Department of Material Processing, Japan); Takayuki Narushima (Tohoku University, Japan); Jean Geringer (Ecole Nationale Supérieure des Mines de Saint Etienne, France)
After the famous recall of the MoM (Metal on Metal) ASR hip implant from Depuy company, on December 2011, a lot of investigations have been carried out on the lifetime of metallic implants. It is worth noting that younger patients are implanted. Thus increasing the lifespan of hip implants is a 'hotspot' research field. This work is dedicated on comparing the fretting-corrosion (metallic sample against PMMA, ±40 µm during 4 hours), see [1,2] behaviors of 316LN stainless steel and Co-Cr-Mo alloys (with or without Ti content, max 1% wt). First of all the effect of proteins in liquid medium is a key-factor on wear. Thus the proteins content is varying from 0-10-20-30 g.L-1. With increasing the proteins content, the wear volume is equal to 20.104 µm3). the lowest wear volume has been highlighted for Co-Cr-Mo alloy with 1% of Ti. On the contrary increasing the concentration of proteins is not beneficial concerning the polymeric material. It is worth noting that the polymeric material has been chosen because the mechanical properties are very close to the ones of bone. Indeed the wear volume of PMMA at 30 g.L-1 of albumin is twice higher than the one measured without any protein. Concerning the number of wear particles this fact does not involve promising outlooks about fretting corrosion degradations. However the softer material is bone in the actual case and the remodeling of the bone always is in progress in human body. Finally, thanks to SEM images, a particular mechanism of lubrication is expected during fretting corrosion degradations. The Ti particles, i.e. particles as TiC, are not degraded during the fretting corrosion process. Thus particular pathways are highlighting after fretting corrosion experiments on the metallic surface. These patterns could be a benefit because promoting the liquid layer and the bearing effect.
Time Period TuM Sessions | Abstract Timeline | Topic D Sessions | Time Periods | Topics | ICMCTF2014 Schedule