Visualization of Cathode Activity for Fe-Rich and Cu-Rich Intermetallic Particles via Cathodic Corrosion from Dioxygen Reduction at Aluminum Alloy 2024-T3

Seegmiller, Jesse C.; Bazito, Reinaldo C.; Buttry, Daniel A.

doi:10.1149/1.1625592

Cited by 22 publications

(35 citation statements)

References 15 publications

(29 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Again, this lower ORR current on the bare and anodized alloy samples results from the presence of simultaneous cathodic ͑ORR͒ and anodic ͑oxide growth͒ processes, as previously described. 22,35 Zr-ODP treated samples were examined using the same procedure as in Fig. 1.…”

Section: Resultsmentioning

confidence: 99%

“…The influence of Zr-ODP treatments on the inhibition of O 2 reduction was examined using a solutionexchange protocol as previously described. 22,35 In these experiments, the sample was initially exposed to N 2 -saturated 0.1 M Na 2 SO 4 , where it was held at −0.8 V for 100 s, followed by a rapid exchange ͑at constant potential͒ to O 2 -saturated 0.1 M Na 2 SO 4 solution, where it was held at the same potential for 1000 s. It has previously been shown that in this wall-jet cell at this flow rate, −0.8 V is on the limiting current plateau for the ORR at both pure Cu and pure Fe and is near the apparent half-wave potential for AA2024-T3. 17,22,35 Thus, measurements at this potential are appropriate for detecting changes in the ORR current density caused by the surface coatings.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Inhibition of O[sub 2] Reduction on AA2024-T3 Using a Zr(IV)-Octadecyl Phosphonate Coating System

Dufek

Buttry

2008

Electrochem. Solid-State Lett.

Self Cite

View full text Add to dashboard Cite

A thin-film coating consisting of Zr͑IV͒ and octadecyl phosphonate provides inhibition of O 2 reduction for AA2024-T3. The coating procedure produces films with thicknesses approaching that of a self-assembled monolayer. Using constant-potential experiments, the current density for the O 2 reduction reaction has been shown to decrease by 2 orders of magnitude following five treatments. Auger electron spectroscopy of the coating shows that both Zr and phosphorus are present at the alloy surface following treatment. Characterization of the coating shows it to be hydrophobic, with the octadecyl chains being in a liquid-like environment.Prevention of corrosion on Cu-rich aluminum alloys such as AA2024 is important due to their widespread use, especially in the aerospace industry. One major inhibition method involves the use of chromate conversion coatings ͑CCCs͒. These coatings are known to work via the formation of Cr oxides at sites on the alloy surface where reductive electrochemistry can occur, thereby blocking reduction of O 2 . 1-3 Due to adverse environmental and health effects associated with CCCs, a push to develop new, less hazardous coating systems is under way. Interest has focused on different means of protecting surfaces from corrosion. [4][5][6][7][8][9][10][11][12][13][14] In several reports, Scully and co-workers have found that treatment with various cerium solutions reduces the oxygen reduction reaction ͑ORR͒ on both Cu and AA2024 surfaces either by diminishing the area of active corrosion sites or by the formation of a barrier over the active intermetallic particles ͑IPs͒. 4,15 Organic-based coatings also have been shown to reduce the ORR current. 11,12,16 These methods have thus far shown varying degrees of inhibition of the corrosion processes of AA2024.Corrosion of aluminum alloys can be strongly affected by the presence of IPs, which are formed during the manufacturing process. 17-21 In many cases, the important cathodic process at IPs is the ORR, in which O 2 undergoes a net four-electron reduction to form OH − in neutral and basic conditions. The resulting high local pH can lead to dissolution of the protective oxide at the alloy surface, thereby damaging the surface and promoting additional redox processes. 22 Thus, O 2 reduction is an important early step in driving corrosion of this and related alloys.This study examines the corrosion inhibition achieved by treating AA2024-T3 with long-chain alkyl phosphonates and Zr͑IV͒. Various approaches to formation of Zr͑IV͒-phosphonate layers have been reported. 23-33 As described below, repetitive treatment of AA2024-T3 surfaces with solutions containing either octadecyl phosphonate ͑ODP͒ or Zr͑IV͒ salts produces a thin-film coating that is effective at suppressing the ORR, even at applied potentials where this process would proceed efficiently at the bare alloy surface. The inhibition is observed to be approximately 2 orders of magnitude and depends on the details of formation of the Zr͑IV͒ ODP thin film. ExperimentalSample preparation.-For both e...

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Inhibition of O[sub 2] Reduction on AA2024-T3 Using a Zr(IV)-Octadecyl Phosphonate Coating System

Dufek

Buttry

2008

Electrochem. Solid-State Lett.

Self Cite

View full text Add to dashboard Cite

show abstract

“…4c, two regions where trenching or particle removal may have taken place are evident ͑shown in rectangles͒; however, these appear to have been caused by IP removal during the polishing process. 6 Other than these two locations, the treated sample shows no trenching adjacent to particles. Confirmation of the presence of the modifying layer was accomplished by acquiring a broad area AES spectrum as well as multiple-point AES spectra on the alloy surface.…”

Section: C325mentioning

confidence: 94%

“…The wall-jet flow cell used for voltammetry and chronoamperometric experiments was previously described. 6,7 This cell used gravitational flow for the delivery of the supporting electrolyte, giving a smooth, pulseless flow. The rate of delivery to the electrode surface was monitored by a downstream digital flowmeter ͑Agilent Technologies͒, ensuring that flow was kept within the range in which the cell was known to obey theory ͑1.55-1.70 mL min −1 ͒.…”

Section: Methodsmentioning

confidence: 99%

Characterization of Zr(IV)–Phosphonate Thin Films Which Inhibit O[sub 2] Reduction on AA2024-T3

Dufek

Buttry

2009

J. Electrochem. Soc.

Self Cite

View full text Add to dashboard Cite

Zr͑IV͒-alkyl-phosphonate and Zr͑IV͒-aryl-phosphonate thin films of varying compositions were investigated for corrosion inhibition capabilities on AA2024-T3. A strong correlation between the alkyl chain length and the ability of these self-assembled systems to inhibit the O 2 reduction reaction at the alloy surface was found. In particular, modification using Zr͑IV͒-octadecylphosphonate initially inhibits O 2 reduction currents by more than 2 orders of magnitude in 0.1 M Na 2 SO 4 at a potential of Ϫ0.80 V vs a saturated calomel electrode and by greater than 95% after 5500 s under similar conditions. Scanning electrochemical microscopy reveals uniform inhibition of cathodic processes. Auger electron spectroscopy confirms the presence of Zr and P in the thin film. Infrared reflection-absorption spectroscopy indicates that the alkyl chains are in a liquidlike environment. Long-term testing of the Zr͑IV͒-octadecyl-phosphonate system in a sulfate-containing solution yields low levels of surface activation, as evidenced by small amounts of trenching adjacent to intermetallic particles and little change in near-surface Cu content.Aluminum alloys commonly used in the aerospace industry, such as AA2024-T3, have many advantageous mechanical characteristics due to the presence of intermetallic particles ͑IPs͒. However, these same particles, especially those rich in Cu, lead to an undesirable corrosion behavior. The reaction of AA2024-T3 with dioxygen is driven by the ability of Cu-rich IPs to behave cathodically of the bulk alloy, allowing the transfer of electrons needed to reduce dioxygen. 1-6 Under neutral and alkaline conditions, dioxygen reduction at IPs results in the production of hydroxide yielding a localized high pH, which can lead to the dissolution of the oxide near the IPs. 6,7 Once the dissolution of the surface oxide has progressed to a certain point, oxidation of Al in the underlying alloy occurs, resulting in the liberation of Al 3+ -containing species into solution or in the formation of a passive oxide layer. 7,8 Equations 1-3 show the redox reactions associated with these processes, which ultimately can lead to mechanical failureChromate conversion coatings ͑CCCs͒ have been widely used as a means of corrosion inhibition on Al alloys. CCCs prevent O 2 reduction through the formation of impermeable Cr oxide layers at the alloy surface which, under some conditions, are capable of selfhealing over damaged areas on the alloy surface. 9-12 Unfortunately, the positive aspects of CCCs are negated by the possible exposure to Cr͑VI͒, which has been shown to have deleterious health and environmental effects, especially during application and repair operations. Thus, environmentally benign corrosion inhibition systems are required. Primarily, the search for such systems has focused on surface coatings that contain Ce oxide and other metal oxides capable of oxygen reduction reaction ͑ORR͒ inhibition, 13-21 mixed Cephosphate coatings, 22-24 conducting polymers that passivate the alloy surface, 25-27 and self-assemble...

show abstract

“…Other studies have looked directly at localized corrosion behavior. Cathodic activity of Fe and Cu rich inclusions on surfaces of Al 2024 have been examined [19,20]. SECM has been used to initiate [21] and detect [22] localized corrosion at steel surfaces.…”

Section: Introductionmentioning

confidence: 99%

Localized attack of a two-phase metal, scanning electrochemical microscopy studies of NiCrMoGd alloys

Lister¹,

Pinhero²,

Trowbridge³

et al. 2005

Journal of Electroanalytical Chemistry

View full text Add to dashboard Cite

Visualization of Cathode Activity for Fe-Rich and Cu-Rich Intermetallic Particles via Cathodic Corrosion from Dioxygen Reduction at Aluminum Alloy 2024-T3

Cited by 22 publications

References 15 publications

Inhibition of O[sub 2] Reduction on AA2024-T3 Using a Zr(IV)-Octadecyl Phosphonate Coating System

Inhibition of O[sub 2] Reduction on AA2024-T3 Using a Zr(IV)-Octadecyl Phosphonate Coating System

Characterization of Zr(IV)–Phosphonate Thin Films Which Inhibit O[sub 2] Reduction on AA2024-T3

Localized attack of a two-phase metal, scanning electrochemical microscopy studies of NiCrMoGd alloys

Contact Info

Product

Resources

About