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Alkaline oxide conversion coatings for aluminum alloys

Description: Three related conversion coating methods are described that are based on film formation which occurs when aluminum alloys are exposed to alkaline Li salt solutions. Representative examples of the processing methods, resulting coating structure, composition and morphology are presented. The corrosion resistance of these coatings to aerated 0.5 M NaCl solution has been evaluated as a function of total processing time using electrochemical impedance spectroscopy (EIS). This evaluation shows that excellent corrosion resistance can be uniformly achieved using no more than 20 minutes of process time for 6061-T6. Using current methods a minimum of 80 minutes of process time is required to get marginally acceptable corrosion resistance for 2024-T3. Longer processing times are required to achieve uniformly good corrosion resistance.
Date: February 1, 1996
Creator: Buchheit, R.G.
Partner: UNT Libraries Government Documents Department

The response of hydrotalcite coated aluminum to sealing with transition metal salt solutions

Description: Objective was to determine if the protective coating could be enhanced by filling intercrystalline spaces or by reinforcing the coating at intermetallic particles by exposure to aqueous transition metal salt solutions. Two oxy-anion analogs to chromate were used: permanganate and molybdate. Ce(III) (as Ce(NO{sub 3}){sub 3}) was also studied. (Al alloys 2024-T3 and 6061-T6 were used as substrates.) Results are summarized. 4 figs, 1 tab, 3 refs.
Date: 1994
Creator: Buchheit, R. G. & Martinez, M. A.
Partner: UNT Libraries Government Documents Department

Aspects of two corrosion processes relevant to military hardware

Description: Corrosion is a leading material degradation mode observed in many military systems. This report contains a description of a small project that was performed to allow some of the important electrochemical aspects of two distinct and potentially relevant degradation modes to be better understood: environmentally assisted cracking (EAC) of aluminum alloys and corrosion in moist salt. Two specific and respective tasks were completed: (A) the characterization of the effect of aluminum microstructural variability on its susceptibility to EAC, and (B) the development of experimental and analytical techniques that can be used to identify the factors and processes that influence the corrosivity of moist salt mixtures. The resultant information constitutes part of the basis needed to ultimately predict component reliability and/or possibly to identify techniques that could be used to control corrosion in critical components. In Task A, a physical model and related understanding for the relevant degradation processes were formulated. The primary result from Task B included the identification and qualitative validation of a methodology for determining the corrosivity of salt mixtures. A detailed compilation of the results obtained from each of these two diverse tasks is presented separately in the body of this report.
Date: November 1, 1997
Creator: Braithwaite, J.W. & Buchheit, R.G.
Partner: UNT Libraries Government Documents Department

Issues for conversion coating of aluminum alloys with hydrotalcite

Description: Hydrotalcite coatings on aluminum alloys are being developed for corrosion protection of aluminum in aggressive saline environments. Coating bath composition, surface pretreatment, and alloying elements in aluminum all influence the performance of these coatings during salt spray testing. The coating bath, comprised of lithium carbonate, requires aging by dissolution of aluminum into the bath in order to grow corrosion resistant coatings. Coatings formed in non- aged baths do not perform well in salt spray testing. The alloying elements in aluminum alloys, especially copper, influence the coating growth and formation leading to thin coatings. The effect of the alloy elements is to limit the supply of aluminum to the coating/electrolyte interface and hinder growth of hydrotalcite upon aluminum alloys.
Date: December 1, 1993
Creator: Drewien, C. A. & Buchheit, R. G.
Partner: UNT Libraries Government Documents Department

Chromate-free corrosion resistant conversion coatings for aluminum alloys

Description: Inorganic polycrystalline hydrotalcite, Li{sub 2}[Al{sub 2}(OH){sub 6}]{sub 2}{center_dot}CO{sub 3}{center_dot}3H{sub 2}O, coatings can be formed on aluminum and aluminum alloys by exposure to alkaline lithium carbonate solutions. This process is conducted using methods similar to traditional chromate conversion coating procedures, but does not use or produce toxic chemicals. The coating provides anodic protection and delays the onset of pitting during anodic polarization. Cathodic reactions are also inhibited which may also contribute to corrosion protection. Recent studies have shown that corrosion resistance can be increased by sealing hydrotalcite coated surfaces to transition metal salt solutions including Ce(NO{sub 3}){sub 3}, KMnO{sub 4} and Na{sub 2}MoO{sub 4}. Results from these studies are also reported.
Date: March 1, 1995
Creator: Buchheit, R.G.; Drewien, C.A.; Martinez, M.A. & Stoner, G.E.
Partner: UNT Libraries Government Documents Department

Field testing results for the strategic petroleum reserve pipeline corrosion control program

Description: Results of two studies conducted as part of the Strategic Petroleum Reserve (SPR) Pipeline Corrosion Control Program are reported. These studies focused on evaluation of rotary-applied concrete materials for internal pipeline protection against the erosive and corrosive effects of flowing brine. The study also included evaluation of liners applied by hand on pipe pieces that cannot be lined by rotary methods. Such pipe pieces include tees, elbows and flanged pipe sections. Results are reported from a corrosion survey of 17 different liner formulations tested at the-Big-Rill SPR Site. Testing consisted of electrochemical corrosion rate measurements made on lined pipe sections exposed, in a test manifold, to flowing SPR generated fluids. Testing also involved cumulative immersion exposure where samples were exposed to static site-generated brine for increasing periods of time. Samples were returned to the laboratory for various diagnostic analyses. Results of this study showed that standard calcium silicate concrete (API RP10E) and a rotary calcium aluminate concrete formulation were excellent performers. Hand-lined pipe pieces did not provide as much corrosion protection. The focus of the second part of the study was on further evaluation of the calcium silicate, calcium aluminate and hand-applied liners in actual SPR equipment and service. It was a further objective to assess the practicality of electrochemical impedance spectroscopy (EIS) for field corrosion monitoring of concrete lined pipe compared to the more well-known linear polarization technique. This study showed that concrete linings reduced the corrosion rate for bare steel from 10 to 15 mils per year to 1 mil per year or less. Again, the hand-applied liners did not provide as much corrosion protection as the rotary-applied liners. The EIS technique was found to be robust for field corrosion measurements. Mechanistic and kinetic corrosion rate data were reliably obtained.
Date: February 1, 1998
Creator: Buchheit, R.G.; Maestas, L.M. & Hinkebein, T.E.
Partner: UNT Libraries Government Documents Department

Ion beam surface treatment: A new technique for thermally modifying surfaces using intense, pulsed ion beams

Description: The emerging capability to produce high average power (10--300 kW) pulsed ion beams at 0.2{minus}2 MeV energies is enabling us to develop a new, commercial-scale thermal surface treatment technology called Ion Beam Surface Treatment (IBEST). This new technique uses high energy, pulsed ({le}500 ns) ion beams to directly deposit energy in the top 1--20 micrometers of the surface of any material. The depth of treatment is controllable by varying the ion energy and species. Deposition of the energy in a thin surface layer allows melft of the layer with relatively small energies (1--10J/cm2) and allows rapid cooling of the melted layer by thermal conduction into the underlying substrate. Typical cooling rates of this process (109 K/sec) are sufficient to cause amorphous layer formation and the production of non-equilibrium microstructures (nanocrystalline and metastable phases). Results from initial experiments confirm surface hardening, amorphous layer and nanocrystalline grain size formation, corrosion resistance in stainless steel and aluminum, metal surface polishing, controlled melt of ceramic surfaces, and surface cleaning and oxide layer removal as well as surface ablation and redeposition. These results follow other encouraging results obtained previously in Russia using single pulse ion beam systems. Potential commercialization of this surface treatment capability is made possible by the combination of two new technologies, a new repetitive high energy pulsed power capability (0.2{minus}2MV, 25--50 kA, 60 ns, 120 Hz) developed at SNL, and a new repetitive ion beam system developed at Cornell University.
Date: August 1, 1995
Creator: Stinnett, R.W.; Buchheit, R.G. & Neau, E.L.
Partner: UNT Libraries Government Documents Department

An anodic dissolution-based mechanism for the rapid cracking, ``pre-exposure`` phenomenon demonstrated by Al-Li-Cu alloys

Description: Al-Li-Cu alloys have been observed to fail in less than 24 hours after removal from a one week immersion in aerated 3.5 w/o NaCl solution. Anodic dissolution-based mechanisms proposed previously for this phenomenon have been amended based on further experiment and characterization of the rapid cracking process. Amendments are based on studies of the relative electrochemical behavior of the microstructural elements in the subgrain boundary region, time to failure SCC testing in a simulated crack solution, evolution of crack potential and pH with time, fractographic examination of failed samples, and X-ray diffraction of films passivating crack walls. Results suggest that an active path exists along subgrain boundaries that is comprised of the highly reactive T{sub 1} (Al{sub 2}CuLi) precipitate phase and a solute depleted zone that does not readily passivate when exposed to the crack environment. The matrix phase does appear to passivate in the crack environment thereby confining the crack to the subgrain boundary region. This active path is enabled when cracks are isolated from a bulk environment, but is disabled otherwise. Potential and pH conditions required for cracking are discussed as is the formation of a hydrotalcite Li{sub 2}[Al{sub 2}(OH){sub 6}]{sub 2}{center_dot}CO{sub 3}{center_dot}3H{sub 2}O film that appears to be responsible for passivating crack walls.
Date: December 31, 1993
Creator: Buchheit, R. G.; Wall, F. D.; Stoner, G. E. & Moran, J. P.
Partner: UNT Libraries Government Documents Department

Non-Chromate Talc Conversion Coatings for Aluminum

Description: A method was developed for applying an inorganic conversion coating on that is procedurally similar to chromate conversion coating methods; this method, however does not use or involve hazardous/toxic chemicals. The coating forms by precipitation involving Al{sup 3+} Li{sup +}, OH{sup {minus}}, CO{sub 3}{sup 2}{minus}, and possibly other anions. This polycrystalline coating is continuous, conformal and persistent in aggressive environments. Coating thicknesses range from several tenths to ten micrometers. Although the outer portions of the coating are porous, the pores do not penetrate to the substrate interface. These coatings do not match the levels of performance offered by commercially available chromate conversion coatings, but are capable of meeting many of the corrosion resistance, electrical resistivity, and paint adhesion requirements established in MIL-C-5541E ``Chemical Conversion Coatings on Aluminum and Aluminum Alloys.`` In this paper, methods for producing the talc coating on aluminum alloys 1100 and 6061-T6 are described and compared to traditional chromate conversion coating methods. Resulting coating structure and composition are described. Performance data for the talc coatings in MIL-C-5541E required tests are presented along with data commercial chromate-based coatings.
Date: January 1, 1994
Creator: Buchheit, R. G.; Drewien, C. A.; Finch, J. L. & Stoner, G. E.
Partner: UNT Libraries Government Documents Department

A correlation between EIS and salt spray proof tests for the corrosion resistance of conversion coated aluminum alloys

Description: In this study, 33 different conversion coatings were applied to 5 different Al alloy substrates. Salt spray exposure testing and EIS (electrochemical impedance spectroscopy) were conducted for comparison. A relation was developed.
Date: September 1, 1996
Creator: Buchheit, R.G.; Martinez, M.A.; Cunningham, M.; Jensen, H. & Kendig, M.W.
Partner: UNT Libraries Government Documents Department

The electrochemical behavior of Ti and Ti alloys subjected to pulsed ion beam surface treatment

Description: Pulsed high-energy ion beams have been used to thermally treat Ti and Ti alloy surfaces to alter the electrochemical response. Two regimes have been explored: rapid melt and resolidification, and ion beam mixing. In this report, results from initial studies are presented exploring effect of these two regimes on the electrochemical behavior of Ti and Ti alloys.
Date: October 1, 1996
Creator: Sorensen, N.R.; Buchheit, R.G.; Renk, T.R.; Grabowski, K.S. & Thompson, M.O.
Partner: UNT Libraries Government Documents Department

Thermal Stability and Aging Characteristics of Chromate Conversion Coatings on Aluminum Alloy 2024-T3

Description: XANES and electrochemical impedance spectroscopes were used in parallel to correlate the amount of Cr(VI) in chromate conversion coatings (CCC) on Al 2024 and their corrosion resistance in order to understand the degradation mechanisms upon aging or heating. Cr(VI) species appear to be immobilized for temperatures higher than 80 C due to dehydration. CCC are shown to be dynamic in the first month of aging with no significant dehydration. Another degradation mechanism involving chemical changes is to be considered.
Date: October 17, 1999
Creator: Laget, V.; Jeffcoate, C.; Isaacs, H. S. & Buchheit, R. G.
Partner: UNT Libraries Government Documents Department

Pulsed ion beam surface treatment for preparing rapidly solidified corrosion resistant steel and aluminum surfaces

Description: Intense, pulsed ion beams were used to melt and rapidly resolidify Types 316F, 316L and sensitized 304 stainless steel surfaces to eliminate the negative effects of microstructural heterogeneity on localized corrosion resistance. Anodic polarization curves determined for 316F and 316L showed that passive current densities were reduced and pitting potentials were increased due to ion beam treatment. Type 304 samples sensitized at 600 C for 100 h showed no evidence of grain boundary attack when surfaces were ion beam treated. Equivalent ion beam treatments were conducted with a 6061-T6 aluminum alloy. Electrochemical impedance experiments conducted with this alloy exposed to an aerated chloride solution showed that the onset of pitting was delayed compared to untreated control samples.
Date: March 1, 1995
Creator: Buchheit, R.G.; Maestas, L.M.; McIntyre, D.C.; Stinnett, R.W. & Greenly, J.B.
Partner: UNT Libraries Government Documents Department

Pulsed Ion Beam Surface Treatment for preparing rapidly solidified corrosion resistant alloy surfaces

Description: IBEST (Ion BEam Surface Treatment) uses a series of 60 to 100 ns ion beam pulses to deposit energy in the topmost 2 to 20 {mu}m of ametal surface to melt it. Areas as large as 1000 cm{sup 2} can be treated by a single pulse. Treated regions that experienced melt were smoother after ion beam treatment. 2 figs, 1 tab, 2 refs.
Date: May 1, 1994
Creator: Buchheit, R. G.; Maestas, L. M.; McIntyre, D. C.; Stinnett, R. W. & Greenly, J. B.
Partner: UNT Libraries Government Documents Department

Ion beam surface treatment: A new capability for rapid melt and resolidification of surfaces

Description: The emerging capability to produce high average power (5--250 kW) pulsed ion beams at 0.2--2 MeV energies is enabling us to develop a new, commercial-scale thermal surface treatment technology called Ion Beam Surface Treatment (IBEST). This technique uses high energy, pulsed ({le}100 ns) ion beams to directly deposit energy in the top 2--20 micrometers of the surface of any material. Depth of treatment is controllable by varying the ion energy and species. Deposition of the energy with short pulses in a thin surface layer allows melting of the layer with relatively small energies and allows rapid cooling of the melted layer by thermal diffusion into the underlying substrate. Typical cooling rates of this process (10{sup 9}10{sup 10} K/sec) cause rapid resolidification, resulting in production of non-equilibrium microstructures (nano-crystalline and metastable phases) that have significantly improved corrosion, wear, and hardness properties. We have conducted IBEST feasibility experiments with results confirming surface hardening, nanocrystaline grain formation, metal surface polishing, controlled melt of ceramic surfaces, and surface cleaning.
Date: April 1, 1994
Creator: Stinnett, R. W.; McIntyre, D. C.; Buchheit, R. G.; Greenly, J. B. & Thompson, M. O.
Partner: UNT Libraries Government Documents Department

Electronic defects and interface potentials for Al oxide films on Al and their relationship to electrochemical properties

Description: The relative electronic defect densities and oxide interface potentials were determined for naturally-occurring and synthetic Al oxides on Al. In addition, the effect of electrochemical treatment on the oxide electrical properties was assessed. The measurements revealed (1) that the open circuit potential of Al in aqueous solution is inversely correlated with the oxide electronic defect density (viz., lower oxide conductivities are correlated with higher open circuit potentials), and (2) the electronic defect density within the Al oxide is increased upon exposure to an aqueous electrolyte at open circuit or applied cathodic potentials, while the electronic defect density is reduced upon exposure to slight anodic potentials in solution. This last result, combined with recent theoretical predictions, suggests that hydrogen may be associated with electronic defects within the Al oxide, and that this H may be a mobile species, diffusing as H{sup +}. The potential drop across the oxide layer when immersed in solution at open circuit conditions was also estimated and found to be 0.3 V, with the field direction attracting positive charge towards the Al/oxide interface.
Date: June 1, 2000
Creator: SULLIVAN,JOHN P.; DUNN,ROBERTO G.; BARBOUR,J. CHARLES; WALL,FREDERICK D.; MISSERT,NANCY A. & BUCHHEIT,R.G.
Partner: UNT Libraries Government Documents Department

High power ion beam (HPIB) modification of one- and two-layer metal surfaces

Description: Intense pulsed high-power ion beams have been demonstrated to produce enhanced surface properties by changes in microstructure caused by rapid heating and cooling of the surface. Additional improvements can be effected by the mixing of a previously deposited thin-film layer (surface alloying or ion beam mixing) into any number of substrate materials. The authors have conducted surface treatment and alloying experiments with Al, Fe, and Ti-based metals on the RHEPP-1 accelerator (0.8 MV, 20 W, 80 ns FHWM, up to 1 Hz repetition rate) at Sandia National Laboratories. Ions are generated by the MAP gas-breakdown active anode, which can yield a number of different beam species including H, N, and Xe, depending upon the injected gas. Enhanced hardness and wear resistance have been produced by treatment of 440C stainless steel, and by the mixing of Pt into Ti-6Al-4V alloy. Mixing of a thin-film Hf layer into Al 6061-T6 alloy (Al-1.0Mg-0.6Si) has improved its corrosion resistance by as much as four orders of magnitude in electrochemical testing, compared with untreated and uncoated Al6061. Experiments are ongoing to further understand the microstructural basis for these surface improvements.
Date: November 1, 1997
Creator: Renk, T.J.; Sorensen, N.R.; Senft, D.C.; Buchheit, R.G.; Thompson, M.O. & Grabowski, K.S.
Partner: UNT Libraries Government Documents Department

Processing and properties of chromate-free conversion coatings on aluminum

Description: A conversion coating method has been developed based on precipitation of Li{sub 2}[Al{sub 2}(OH){sub 6}]{sub 2}{center_dot}CO{sub 3}{center_dot}3H{sub 2}O from alkaline lithium salt solutions. The process is procedurally similar to chromate conversion coating but does not use or produce hazardous chemicals. The coating that forms is polycrystalline, continuous and conformal. The coating meets the MIL-C-5541E corrosion resistance, electrical contact resistance and paint adhesion requirements for certain aluminum alloys, but does not match the levels of performance exhibited by chromate conversion coatings. In this paper, methods for producing the coating are described. Corrosion resistance has been characterized using electrochemical impedance spectroscopy and salt spray exposure. The structural, compositional and property changes attending post-coating thermal exposure are discussed. Performance in standardized corrosion, electrical and paint adhesion tests is also presented.
Date: December 31, 1994
Creator: Buchheit, R. G.; Drewien, C. A.; Martinez, M. A. & Stoner, G. E.
Partner: UNT Libraries Government Documents Department

Processing of aluminum 7075-T73 components after prolonged storage

Description: Three years ago, production requirements for a T73-tempered aluminium 7075 (Al 7075-T73) component were curtailed and the ``in-process`` parts were stored. During recent attempts to complete processing, visible defects were discovered in this component. Defects at such an early stage in the 20+ year lifetime of the component pose reliability concerns. Chemical and microstructural analysis, mechanical testing, and corrosion evaluation were performed to determine the impact of the defects on material properties.
Date: June 1, 1996
Creator: Guilinger, T.R.; Stevenson, J.O.; Yang, R.G.; Buchheit, R.G.; Schmale, D.T.; Shin, K. et al.
Partner: UNT Libraries Government Documents Department

Pit initiation in AlO{sub x}/Al thin films

Description: The electrochemical responses of AlO{sub x}/Al thin films have been investigated as a function of film growth conditions which produce films with different grain orientation, size and morphology. Films with smooth, 150 nm diameter, randomly oriented grains show a higher pitting potential and lower passive current than those films with large grain-boundary grooving from a mixture of smooth micron-sized, (200)-oriented grains and 300--500 nm diameter, (220)-oriented grains. These results suggest that surface roughness from grain-boundary grooving affects the pitting resistance more strongly than does the grain boundary density.
Date: December 1998
Creator: Son, K. A.; Barbour, J. C.; Missert, N.; Wall, F. D.; Copeland, R. G.; Martinez, M. A. et al.
Partner: UNT Libraries Government Documents Department

THE INFLUENCE OF NANOENGINEERED Cu DEFECTS ON ALUMINUM PITTING INITIATION

Description: Nanoengineering technologies have been used to generate well defined arrays of pure Cu islands within an Al thin film matrix in order to examine the impact of noble particle defects on the initiation of metastable pitting. The Cu particles form local galvanic cells with the surrounding Al matrix and drive metastable corrosion. Electrical isolation of the Cu particles from the Al occurs due to selective Al dissolution and appears to correlate to cessation of metastable events. Distributions of parameters related to the electrochemical signature of an event suggests that size and spacing of particles do not impact the signatures of individual events. However, event frequency data indicate that the propensity for a structure to induce localized events is linked to Cu island diameter and separation.
Date: November 1, 1999
Creator: WALL,F.D.; SON,K.A.; MISSERT,N.A.; BARBOUR,J.C.; MARTINEZ,M.A.; ZAVIDIL,K.R. et al.
Partner: UNT Libraries Government Documents Department

PIT INITIATION IN AlO{sub X}/Al THIN FILMS

Description: The electrochemical responses of AlO{sub x}/Al thin films have been investigated as a function of film growth conditions which produce films with different grain orientation, size and morphology. Films with smooth, 150 nm diameter, randomly oriented grains show a higher pitting potential and lower passive current than those films with large grain-boundary grooving from a mixture of smooth micron-sized, (200)-oriented grains and 300--500 nm diameter, (220)-oriented grains. These results suggest that surface roughness from grain-boundary grooving affects the pitting resistance more strongly than does the grain boundary density.
Date: November 1, 1998
Creator: SON,K.A.; BARBOUR,J.C.; MISSERT,N.; WALL,F.D.; COPELAND,R.G.; MARTINEZ,M.A. et al.
Partner: UNT Libraries Government Documents Department

Crevice Corrosion Initiation at Engineered Cu-Rich Defects in Al Thin Films

Description: Engineered Cu-rich islands were fabricated on an Al thin film to investigate pit initiation mechanisms at noble particles. X-ray photoelectron spectroscopy confirms that the thin film Cu-rich islands interdiffuse with the underlying Al substrate to form Al{sub 2}Cu islands. The defect arrays exhibit open circuit potential fluctuations whose magnitude and frequency increase as defect spacing decreases for constant island size and cathode/anode ratio. Post-exposure examination by energy dispersive spectroscopy (EDS) shows that the Al beneath the Cu-rich island dissolves with a crevice geometry. Engineered Al islands fabricated under identical conditions do not induce crevice corrosion in the vicinity of the Al defects. These results suggest that the Al dissolution is driven by the galvanic coupling between the noble island and matrix, and/or by a local change in chemistry, rather than by the presence of a defective oxide in the vicinity of the island.
Date: October 14, 1999
Creator: BARBOUR,J. CHARLES; BUCHHEIT,R.G.; COPELAND,ROBERT GUILD; ISAACS,H.S.; JEFFCOATE,C.S.; MARTINEZ,MICHAEL A. et al.
Partner: UNT Libraries Government Documents Department

Stress corrosion cracking of Al-Li-Cu-Zr alloy 2090 in aqueous Cl sup minus and mixed CO sub 3 sup 2 minus /Cl sup minus environments

Description: A comparison of the short-transverse SCC behavior of 2090 in pH 5.5 Cl{sup {minus}} and alkaline CO{sub 3}{sup 2 {minus}}/Cl{sup {minus}} solutions using a static load smooth bar SCC technique was made. In the alkaline CO{sub 3}{sup 2 {minus}}/Cl{sup {minus}} solutions, E{sub br} for the {alpha}-Al matrix phase was 0.130 V more positive than the E{sub br} of the subgrain boundary T{sub 1} phase. In this environment, stress corrosion cracking test specimens subjected to potentials in the window defined by the two breakaway potentials failed along an intersubgranular path in less than an hour. In the Cl{sup {minus}} environment, the E{sub br} values for the two phases were nearly equal and this rapid SCC condition could not be satisfied; accordingly SCC failures were not observed. Rapid SCC failure of 2090 in CO{sub 3}{sup 2 {minus}}/Cl{sup {minus}} in our static load, constant immersion experiments appear to be related to recently reported pre-exposure embrittlement'' failures induced by immersing stressed specimens removed into ambient laboratory air after immersion in aerated NaCl solution for 7 days. In those experiments, specimens failed in less than 24 hours after removal from solution. Our polarization experiments have shown that the corrosion behavior of T{sub 1}, CO{sub 3}{sup 2 {minus}}/Cl{sup {minus}} environments, but the {alpha}-Al phase crack walls, is rapidly passivated. X-ray diffraction of the films which formed in simulated crevices suggests that this passivating film belongs to a class of compounds known as hydrotalcites.
Date: January 1, 1991
Creator: Buchheit, R.G. (Sandia National Labs., Albuquerque, NM (USA)); Wall, F.D.; Stoner, G.E. (Virginia Univ., Charlottesville, VA (USA). Dept. of Materials Science) & Moran, J.P. (National Inst. of Standards and Technology, Gaithersburg, MD (USA))
Partner: UNT Libraries Government Documents Department