The effects of hyperglycemia, altered cell function, or inflammatory mediators on implant corrosion are not well studied; yet, these effects are critical to implant biocompatibility and osseointegration. Because implant placement is burgeoning, patients with medically compromising systemic conditions such as diabetes are increasingly receiving implants, and the role of other inflammatory diseases on implant corrosion also needs investigation. In the current study, the corrosion properties of commercially available, machined titanium implants were studied in blood, cultures of monocytic cells, and solutions containing elevated dextrose concentrations. Implant corrosion was estimated by open circuit potentials, linear polarization resistance, and electrical impedance spectroscopy (EIS) for 26 h. In selected samples, THP1 monocytic cells were activated for 2 h with Lipopolysaccharide prior to implant exposure, and IL-1beta secretion was measured to assess the affect of the implants on monocyte activation. Implants under conditions of inflammatory stress exhibited more negative E(corr) values, suggesting an increased potential for corrosion. Linear polarization measurements detected increased corrosion rates in the presence of elevated dextrose conditions over PBS conditions. EIS measurements suggested that implants underwent surface passivation reactions that may have limited corrosion over the short term of this test. This result was supported by cyclic polarization tests. IL-1beta secretion was not altered under conditions of corrosion or implant exposure. The results suggest that inflammatory stress and hyperglycemia may increase the corrosion of dental endosseous titanium-based implants, but that longer, more aggressive electrochemical conditions may be necessary to fully assess these effects.

Endosseous dental implants use is increasing in patients with systemic conditions that compromise wound healing. Manufacturers recently have redesigned implants to ensure more reliable and faster osseointegration. One design strategy has been to create a porous phosphate-enriched titanium oxide (TiUnite) surface to increase surface area and enhance interactions with bone. In the current study, the corrosion properties of TiUnite implants were studied in cultures of monocytic cells and solutions simulating inflammatory and hyperglycemic conditions. Furthermore, to investigate whether placement into bone causes enough mechanical damage to alter implant corrosion properties, the enhanced surface implants as well as machined titanium implants were placed into human cadaver mandibular bone, the bone removed, and the corrosion properties measured. Implant corrosion behavior was characterized by open circuit potentials, linear polarization resistance, and electrical impedance spectroscopy. In selected samples, THP1 cells were activated with lipopolysaccharide prior to implant exposure to simulate an inflammatory environment. No significant differences in corrosion potentials were measured between the TiUnite implants and the machined titanium implants in previous studies. TiUnite implants exhibited lower corrosion rates in all simulated conditions than observed in PBS, and EIS measurements revealed two time constants which shifted with protein-containing electrolytes. In addition, the TiUnite implants displayed a significantly lower corrosion rate than the machined titanium implants after placement into bone. The current study suggests that the corrosion risk of the enhanced oxide implant is lower than its machined surface titanium implant counterpart under simulated conditions of inflammation, elevated dextrose concentrations, and after implantation into bone.

Pitting corrosion, nitrite concentration fell outside that specified in the corrosion control program for HLW 30 A537SRNL-STI-2014-00281 Revision 0 design basis, but in the regions with cracking and cavitation the K-3 corrosion rate is at or greater than the DWPF design basis.5. The cavitation is likely due to the proximity of the refractory coupon to the bubbler orifice but the cracking is related to the Fe° depletion caused by excessive nitric acid used in the glycolic acid CEF campaign.The expected performance of the materials of construction within the CPC, specifically C276, Ultimet® and Stellite® at boiling temperatures, is questionable due to the susceptibility to localized corrosion identified during this testing. Since the glycolate anion concentration is at the highest in the CPC for the whole HLW processing system, determining operating limits where localized corrosion is not a concern is stressed. Additional testing for these materials is recommended to better understand the limits of these results and identify conditions for acceptable performance in service.These proposed tests would include performing electrochemical testing with formic acid based SRAT/SME supernates, which would provide a correlation between accelerated electrochemical test results and observed performance of components within the CPC and with glycolic acid based SRAT/SME supernates at levels of aggressive species (chloride, sulfate and mercury) where localized corrosion does not occur. Similar simulants would be used in hot-wall tests to verify that localized corrosion also does not occur under heat transfer conditions. Finally, a coupon immersion test is recommended to verify that the accelerated results of the electrochemical test occur with time during an extended exposure in the coupon test.Additional testing was also recommended for other materials where the presence of the glycolate anion impacted test results. These tests were recommended to better identify the temperature and glycolic acid limits for acceptable performance of the materials of construction, especially those susceptible to localized corrosion.1. Coupon immersion test with 304L in 70% glycolic acid at actual service temperature to determine if pitting occurs.2. Hot-wall testing for G30 and G3 in waste stream simulants without glycolic acid present for comparison to results with glycolate anion present, where pitting and crevice corrosion was observed.3. Metallurgical examination of the inner diameter of I690 pipe used in fabrication of melter bubbler to determine presence of cracks, which would reduce effective thickness and act as stress concentrators.4. Perform modified ASTM C621 tests in glycolic acid feeds to determine impact of glycolic acid vs. formic acid with and without the impact of Ar bubbling, i.e. all the formic acid flowsheet corrosion data has been derived in non-bubbled pilot scale melters except for the CEF glycolic acid campaign. This testing should suffice to get more precise comparative corrosion data for the K-3.viii Revision TABLE OF CO...

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