Exfoliation Corrosion Susceptibility Research Articles

Metallurgical and corrosion characteristics of AA7075 alloy reinforced with Nickel foam

ABSTRACT The current work investigates the metallurgical and corrosion characteristics of the interface between Nickel foam and AA7075 alloy. Nickel foam is conjoined with AA7075 alloy (composite) through a melt-infiltration technique. The composite specimen is characterized for microstructure, microhardness, microhardness, exfoliation corrosion susceptibility, and electrochemical corrosion parameters, including corrosion potential, corrosion current density, and polarization resistance. Also, the influence of T6 heat treatment on the corrosion of the composite specimen is analyzed. The texture, morphology, and composition of the interface and corroded surface are comprehensively analyzed using instrumental analytical techniques such as Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD), Energy-Dispersive X-ray Spectroscopy (EDS), and X-ray diffraction. The results indicate that T6 heat treatment increases the corrosion resistance of the composite specimen.

Effect of Grain Structure and Quenching Rate on the Susceptibility to Exfoliation Corrosion in 7085 Alloy.

The influence of grain structure and quenching rates on the exfoliation corrosion (EXCO) susceptibility of 7085 alloy was studied using immersion tests, optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and scanning transmission electron microscopy (STEM). The results show that as the cooling rate decreases from 1048 °C/min to 129 °C/min; the size of grain boundary precipitates (GBPs); the width of precipitate-free zones (PFZ); and the content of Zn, Mg, and Cu in GBPs rise, leading to an increase in EXCO depth and consequently higher EXCO susceptibility. Meanwhile, there is a linear relationship between the average corrosion depth and the logarithm of the cooling rate. Corrosion cracks initiate at the grain boundaries (GBs) and primarily propagate along the HAGBs. In the bar grain (BG) sample at lower cooling rates, crack propagation along the sub-grain boundaries (SGBs) was observed. Compared to equiaxed grain (EG) samples, the elongated grain samples exhibit larger GBPs, a wider PFZ, and minor compositional differences in the GBPs, resulting in higher EXCO susceptibility.

Effect of Cu content on intergranular corrosion and exfoliation corrosion susceptibility of Al−Zn−Mg−(Cu) alloys

The effect of Cu content on intergranular corrosion (IGC) and exfoliation corrosion (EXCO) susceptibility of Al−Zn−Mg−(Cu) alloys was investigated by electrochemical test, immersion test, electron backscattered diffraction, optical microscope, scanning electron microscope, scanning transmission electron microscope and scanning Kelvin probe force microscope. As Cu content increases from 0 to 2.6 wt.%, IGC susceptibility increases, while EXCO susceptibility first increases and then decreases, reaching the maximum at Cu content of 1 wt.%. With the increase of Cu content, the area fraction of recrystallized grains increases, and the aspect ratio of recrystallized grains first decreases and then increases; moreover, the Volta potential difference between grain boundary precipitates (GBPs) and the matrix increases, making GBPs more susceptible to corrosion. The initiation and propagation of IGC and EXCO are discussed mainly based on the features of GBPs, grain structure, and the Volta potential difference between GBPs and the matrix.

Effect of Cu content on quenching sensitivity relative to exfoliation corrosion susceptibility of Al-Zn-Mg-(Cu) alloys

The effect of Cu content on quenching sensitivity relative to exfoliation corrosion susceptibility of Al-Zn-Mg-(Cu) alloys was investigated by electrochemical test, immersion test, optical microscopy, electron backscattered diffraction, scanning electron microscopy, scanning transmission electron microscopy and scanning Kelvin probe force microscopy. As quenching rate decreases from 400 °C/s to 4 °C/s, exfoliation corrosion (EXCO) susceptibility increases for Cu-containing alloys (0.5–2.6 wt%); while for the Cu-free alloy, EXCO susceptibility first increases and then decreases, reaching the lowest at the quenching rate of 70 °C/s, and then continues to increase. Quenching sensitivity of the Cu-free alloy is the lowest, and that of Cu-containing alloys is similar. The decrease of quenching rate or the increase of Cu content leads to a larger difference in the Volta potential between grain boundary precipitates (GBPs) and the matrix. Corrosion tends to propagate only along grain boundaries at high quenching rates, but along both grain boundaries and subgrain boundaries below a critical quenching rate, which increases with increasing Cu content. The corrosion behavior has been discussed primarily based on the features of GBPs and precipitates free zones, and the Volta potential difference between GBPs and the matrix. • Quenching sensitivity is the lowest for Al-Zn-Mg and similar for Al-Zn-Mg-Cu. • EXCO susceptibility of Al-Zn-Mg-Cu is higher at a lower quench rate. • EXCO susceptibility of Al-Zn-Mg is lowest at the quench rate of 70 °C/s. • Corrosion path is related to quench rate and Cu content. • Potential difference is larger at a lower quench rate or a higher Cu content.

Effect of cooling rate and grain structure on the exfoliation corrosion susceptibility of AA 7136 alloy

The effect of cooling rate and grain structure on exfoliation corrosion susceptibility of AA 7136 alloy was investigated by open-circuit potential (OCP) measurement, immersion test, optical microscopy (OM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), scanning transmission electron microscopy (STEM), and scanning Kelvin probe force microscopy (SKPFM).The results showed that quench-induced η phase formed with a decrease in the cooling rate from 244 °C/s to 1.3 °C/s after solution heat treatment, thereby increasing exfoliation corrosion susceptibility. The quench-induced impact is the lowest, intermediate, and highest in the specimen with large elongated recrystallized grains (large-REX), fine recrystallized grains (fine-REX) and elongated unrecrystallized grains (elongated-UNREX), respectively. The Volta potential difference between the matrix and grain boundary precipitates was the lowest (68.3 ± 6.6 mV) in large-REX specimens, intermediate (88.6 ± 11.3 mV) in fine-REX specimens, and highest (137.6 ± 27.3 mV) in elongated-UNREX specimens. The reason has been discussed in detail based on the features of grains, and quench-induced change in the microstructural and microchemical features at grain boundaries in different specimens.

Exfoliation corrosion susceptibility in the zones of friction stir welded AA2098-T351

In the present study, the exfoliation susceptibility of the weld zones in friction stir welded AA2098-T351 was compared with that of the base metal (BM) according to ASTM G34 standard practice. Friction stir welding (FSW) had a significant effect on the microstructure of the Al alloy tested and the susceptibility to exfoliation was strongly affected by the microstructure. Different features of corrosion attack and exfoliation susceptibility were observed when the zones affected by FSW were tested isolated or coupled. Also, the near-surface deformed layer had an important effect on the Al alloy susceptibility to exfoliation. These are the main findings of this work. The corrosion features were correlated with the microstructural modifications related to the welding process and with the electrochemical response. The T1 phase morphology, distribution and size were critical for exfoliation susceptibility. The stir zone (SZ) was the zone most resistant to exfoliation. However, resistance to exfoliation varied with the temperatures reached in the heat affected zones (HAZs). The HAZ exposed to the lowest temperatures during welding, HAZ (LT), was the most susceptible to exfoliation, whereas the HAZ exposed to the highest temperatures, HAZ (HT), presented high resistance to exfoliation, similarly to the SZ. The ASTM-G34 practice was an effective and useful method in identifying the different exfoliation resistances of the BM and the various zones affected by FSW. The results of this practice were supported by electrochemical impedance spectroscopy (EIS) tests.

Microstructure Evolution and the Resulted Influence on Localized Corrosion in Al-Zn-Mg-Cu Alloy during Non-Isothermal Ageing.

A non-isothermal ageing process was proposed for an Al-Zn-Mg-Cu alloy aiming to accommodate the slow heating/cooling procedure during the ageing of large components. The evolution of microstructure and microchemistry was analyzed by using transmission electron microscopy, high-angle annular dark field imaging, and energy dispersive spectrometry. The age-hardening of the alloy was examined to evaluate the strengthening behavior during the non-isothermal process. The corrosion behavior was investigated via observing the specimens immersed in EXCO solution (solution for Exfoliation Corrosion Susceptibility test in 2xxx and 7xxx series aluminum alloys, referring ASTM G34-01). Secondary precipitation was observed during the cooling stage, leading to increased precipitate number density. The distribution of grain boundary precipitates transits from discontinuous to continuous at the cooling stage, due to the secondary precipitation’s linking-up effect. The solutes’ enrichment on grain boundary precipitates and the depletion in precipitate-free zones develops during the heating procedure, but remains invariable during the cooling procedure. The corrosion in NIA (Non-isothermal Ageing) treated specimens initiates from pitting and then transits to intergranular corrosion and exfoliation corrosion. The transition from pitting to intergranular corrosion is very slow for specimens heated to 190 °C, but accelerates slightly as the cooling procedure proceeds. The transition to exfoliation corrosion is observed to be quite slow in all specimens in non-isothermal aged to over-aged condition, suggesting a corrosion resistance comparable to that of RRA condition.

Developing a Framework for Improved Accelerated Testing of Aluminum-Lithium Alloys

Third generation Aluminum-lithium (Al-Li) alloys such as AA2060 are attractive for aerospace applications due to their high strength-to-weight ratios and their corrosion resistance during seacoast exposures.1 However characterizing these alloys in laboratory corrosion tests can be difficult as the results from conventional accelerated tests do not always agree with seacoast results. For example, ASTM G34 is a standard test for exfoliation corrosion, which is a form of localized attack that produces blisters when corrosion products due to intergranular attack produce a wedging pressure and lift un-attacked grains upward. This test was developed for alloys 7075 and 7178,2 but is considered applicable to 2xxx and 7xxx series aluminum alloys.3 However when Al-Li alloys 2099 and 2060 are tested in ASTM G34, the trend in exfoliation susceptibility over different aging conditions is opposite to the trend observed after seacoast exposures.4 This kind of disagreement between laboratory testing and seacoast exposure slows down the process of optimizing aging practices for new products. As new generation aluminum alloys become available, improved accelerated corrosion tests must be designed to accurately predict the corrosion response under atmospheric conditions in a short time. Many different approaches can be used to accelerate corrosion (high testing temperature, high chloride content in the testing solution, added oxidizing agents, very acidic or very alkaline testing solution etc.), and each of these parameters alters the corrosion response by changing electrochemical kinetics. Improved accelerated test protocol requires a better understanding of the relationship between testing parameters, electrochemical kinetics, and corrosion morphology. The purpose of the current study is to develop a framework for new accelerated corrosion test design by connecting attack morphology to electrochemical kinetics. Both the exfoliation susceptible under-aged (T36) temper and the exfoliation resistant near peak-aged (T86) temper of Al-Cu-Li alloy 2060 were considered in this work. ASTM G343, ANCIT2, and ASTM G85-A25 were used to study the impact of various testing parameters on the corrosion response of AA2060. Electrochemical measurements were used to determine corrosion potential (Ecorr) and polarization resistance (Rp) during standard and modified versions of each test in-situ. After each exposure, samples were also cross-sectioned and examined with optical microscopy. Results indicate that for immersion tests (ASTM G34 and ANCIT), testing temperature has a significant impact on anodic kinetics, while solution pH affects cathodic kinetics. The higher testing temperature of ANCIT led to faster anodic kinetics and faster formation of exfoliation in the T36 temper compared to ASTM G34. For salt spray testing (ASTM G85-A2), it was found that the lower bound of relative humidity (RH) during RH cycling had an impact on Rp as well as extent of attack. When the test was run with a lower bound of 60% RH, Rp remained relatively constant throughout the salt spray, dry air purge, and dwell portions of the cycle. However when the test was run with a lower bound of 20% RH, Rp increased (corresponds to a decrease in corrosion rate) during the dry air purge and dwell periods. This time at very low RH resulted in much slower development of exfoliation on the T36 temper compared to the test with a lower RH bound of 60%. Acknowledgements This work is supported by the Office of the Undersecretary of Defense Corrosion University Pilot Program under the direction of Dr. D. Dunmire, Rolls-Royce, and the Virginia Space Grant Consortium. References R.J. Rioja, J. Liu, Metal. Mater. Trans. A 43 (2012): p. 3325-3337S. Lee, B.W. Lifka, “Modification of the EXCO Test Method for Exfoliation Corrosion Susceptibility in 7XXX, 2XXX, and Aluminum-Lithium Alloys,” in New Methods for Corrosion Testing of Aluminum Alloys, eds. V.S. Agarwala, G.M. Ugiansky, STP 1134 (West Conshohocken, PA: ASTM International, 1992), p. 1-19.ASTM G34-1, “Standard Test Method for Exfoliation Corrosion Susceptibility in 2XXX and 7XXX Series Aluminum Alloys” (West Conshohocken, PA: ASTM International, 2001), p. 1-7.J.P. Moran, F.S. Bovard, J.D. Chrzan, P. Vandenburgh, “Corrosion Performance of New Generation Aluminum-Lithium Alloys for Aerospace Applications,” 13th Int. Conf. on Aluminum Alloys, held June 3-7, 2012 (Hoboken, NJ: John Wiley & Sons, Inc., 2012).ASTM G85-A2, “Standard Practice for Modified Salt Spray (Fog) Testing” (West Conshohocken, PA: ASTM International, 2002), p. 1-14.

7075-T6 aluminium alloy exfoliation corrosion sensitivity and electrochemical impedance spectroscopy under stress

Exfoliation corrosion susceptibility under tensile-bending stress of 7075-T6 aluminium alloy was tested with a self-made tri-fulcrums loading fixture. The test results of both microscopic characterisation and electrochemical impedance spectroscopy indicate that the alloy's exfoliation corrosion susceptibility in exfoliation corrosion solution increases evidently for tensile-bending stress. The electrochemical impedance spectroscopy of the loaded sample soaked for 12 hours manifests double capacitance arcs as the mark of propagated exfoliation corrosion, which takes 24 hours for the unloaded one to reach the same results. Results analysed by equivalent circuit model also prove the accelerating effect of tensile-bending stress on exfoliation corrosion susceptibility.

Exfoliation corrosion of an extruded low-Cu-containing AA7003-T6 profile with a partially recrystallised grain structure

The effect of a partially recrystallised grain structure on the exfoliation corrosion susceptibility of a peak aged (T6) extruded low-Cu-containing AA7003 profile was evaluated using the ASTM G34 standard test method coupled with a metallographic examination. Both the as-extruded (recrystallised) and milled (non-recrystallised) starting surfaces were assigned the same ASTM G34 visual classification of EB (moderate exfoliation corrosion) after 48 h immersion. Damage initiated on the as-extruded starting surface as pitting corrosion in the recrystallised coarse-grained surface layer and propagated as exfoliation corrosion in the non-recrystallised fibrous interior once the surface layer was penetrated. A complementary scanning transmission electron microscopy (STEM) examination suggested that there was not likely a marked difference in the distribution of Mg, Zn and Cu across the precipitation free zone (PFZ) and grain-boundary precipitates between the recrystallised and non-recrystallised grain structures. This indicates that the transition from pitting corrosion to exfoliation corrosion in the peak aged AA7003 alloy was controlled more so by the variation in some other microstructure parameter across the grain-boundary region and less so by the variation in the microchemistry (Cu content in particular).

Effect of aging on corrosion property, electrochemical behavior and microstructure of AlZnMgCu alloy

The effect of aging treatment on corrosion behavior of AlZnMgCu alloy was investigated by means of intergranular corrosion test, exfoliation corrosion test, electrochemical analysis, and transmission electron microscope. The results show that intergranular and exfoliation corrosion susceptibility of the studied alloy decrease gradually with increasing aging time. This is further confirmed by potentiodynamic polarization and electrochemical impedance spectroscopy tests, which show the corrosion resistance increased and corrosion density decreased with prolonging aging time. Moreover, the variation of impedance parameters simulated in terms of an equivalent electrical circuit present better reflection to the corrosion process, thus give valuable information to evaluate the corrosion property. According to microstructural observation, the morphology and distribution of grain boundary precipitate varied with aging treatment have decisive influence to the corrosion behavior.

Influence of multi-step heat treatments in creep age forming of 7075 aluminum alloy: Optimization for springback, strength and exfoliation corrosion

Multi-step heat treatments comprise of high temperature forming (150 °C/24 h plus 190 °C for several minutes) and subsequent low temperature forming (120 °C for 24 h) is developed in creep age forming of 7075 aluminum alloy to decrease springback and exfoliation corrosion susceptibility without reduction in tensile properties. The results show that the multi-step heat treatment gives the low springback and the best combination of exfoliation corrosion resistance and tensile strength. The lower springback is attributed to the dislocation recovery and more stress relaxation at higher temperature. Transmission electron microscopy observations show that corrosion resistance is improved due to the enlargement in the size and the inter-particle distance of the grain boundaries precipitates. Furthermore, the achievement of the high strength is related to the uniform distribution of ultrafine η′ precipitates within grains.

Relationship between alloy composition, microstructure and exfoliation corrosion in Al–Zn–Mg–Cu alloys

The exfoliation corrosion (EFC) susceptibility of several 7000 Aluminium alloys has been studied after a variety of heat treatments using two independent corrosion tests (standard EXCO test and an electrochemical test based on potential transients analysis), together with detailed microstructural examinations. It is proposed that depending on heat treatment EFC may occur via two different mechanisms: inter-granular dissolution induced damage (IDD) or inter-granular fracture induced damage (IFD). The coexistence of these two mechanisms, leading to EFC, and their relative predominance explain the influence of alloy composition and heat treatment on EFC susceptibility via the confrontation of the two corrosion tests.

Influence of nitrogen implantation on the localized corrosion resistance of different tempers of AA7075 aluminium alloy

AbstractThis paper reports the study of the effect of nitrogen implantation on the localized corrosion resistance of the passive layers generated on different tempers of AA7075 aluminium alloy.Cyclic potentiodynamic polarization has been employed to analyze the resistance to localized corrosion of the alloys in a chloride medium, whereas exfoliation corrosion susceptibility test (EXCO‐Test) have been performed to evaluate the influence of nitrogen implantation on exfoliation resistance.Results show that nitrogen implantation (dose of 2 × 1017 N+ ions/cm2 and energy of 50 keV) does not have a clear positive effect on exfoliation resistance as it is evident on EXCO testing. However, electrochemical experiments performed in 1 mM NaCl solution reveal a light increase on localized corrosion resistance on implanted alloys. Moreover, the results demonstrate that the susceptibility of the 7075 aluminium alloy to different types to localized corrosion such as, pitting, intergranular and exfoliation greatly depends on the aging treatment, even under implantation conditions. Copyright © 2010 John Wiley & Sons, Ltd.

Exfoliation corrosion of 7150 Al alloy with various tempers and its electrochemical impedance spectroscopy in EXCO solution

AbstractThe exfoliation corrosion susceptibility and electrochemical impedance spectroscopy (EIS) of 7150 Al alloys with T6, T73, and RRA (retrogression at 175 °C for 3 h) tempers in EXCO solution were investigated. The anodic equilibrium precipitate η(MgZn2) is continuous or closely spaced at the grain boundaries in the 7150‐T6 Al alloy, resulting in its greatest susceptibility to exfoliation corrosion. The grain boundary η precipitates in the RRA and T73 treated 7150 Al alloys are coarsened and show a clear discontinuous nature; they possess similar exfoliation corrosion sensitivity and their exfoliation corrosion resistance is greatly increased. At the beginning of immersion in EXCO solution, the EIS plot of the 7150 Al alloys is composed of a capacitive arc in the high to medium frequency range and an inductive component in the medium to low frequency range. As immersion time is increased, exfoliation corrosion with different corrosion ratings occurs on the surface of the 7150 Al alloy with various tempers, two capacitive arcs appear in the high to medium and medium to low frequency ranges, respectively. The fitted medium to low frequency capacitance C2 of 7150‐T6 Al alloy, corresponding to the new surface caused by the exfoliation corrosion, is much greater than that of the T73 and RRA treated 7150 Al alloy, which is consistent with the greatest exfoliation corrosion susceptibility of the 7150‐T6 Al alloy.

Mechanical properties, corrosion behaviors and microstructures of 7075 aluminium alloy with various aging treatments

The influence of two novel aging treatments, T6I6 (130 °C, 80 min + 65 °C, 240 h+130 °C, 18 h) and high-temperature pre-precipitation(HTPP) aging (445 °C, 30 min+120 °C, 24 h) on the tensile properties, intergranular corrosion, exfoliation corrosion behaviors and microstructures of 7075 Al alloy was studied, which were compared with the T6, T73 and RRA treatments. Fine η′ precipitate with high density was obtained in the alloy with the T6 and RRA treatments. The η′ precipitate density in the HTPP aged alloy is decreased due to the formation of coarse particles during the pre-precipitation process at high temperature of 445 °C. The 7075-T6I6 alloy possesses higher precipitate density and whole precipitate volume fraction within the grain than the 7075-T73 alloy, and its whole precipitate volume fraction is even greater than that of the 7075-T6 alloy. Compared with T6 treatment, the RRA, T73, T6I6 and HTPP aging treatments cause the discontinuous distribution of the η precipitates at the grain boundary, which decreases the intergranular corrosion and exfoliation corrosion susceptibility of the alloy. Meanwhile, the T6I6 and RRA treatments can keep the high strength of the 7075 Al alloy, but the studied HTPP aging and T73 treatments lower its strength.

Influence of processing on the properties of the aluminium alloy 2025 with a zirconium addition

The influence of hot deformation and alloy composition on the tensile properties, tear toughness and exfoliation corrosion susceptibility of aluminium alloy 2025 forgings has been investigated. Two casts of 2025 were used to make extrusion billets. These were of standard composition within the 2025 specification, and a composition outside the permitted range but reflecting more modern alloy design with a 0.12 wt.% addition of zirconium. Billets were hot extruded and hot forged at a range of temperatures expected to produce unrecrystallised, partially and fully recrystallised microstructures. The main objective of the compositional variation was to alter the wrought grain refining intermetallic phase, allowing more control of the grain size produced by heat treatment. After the application of a standard heat treatment, tensile and tear toughness properties were determined. Exfoliation tests were performed in accordance with ASTM-G34. The exfoliation susceptibility and mechanical properties of 2025 forgings have been found to exhibit a dependence on microstructure developed during hot forming and heat treatment but the Zr addition was ineffective in producing a refined microstructure.

Influence of the Nickel on the Corrosion Behavior of Al-Mg-Sc-Zr Alloy

The corrosion behavior of cold worked Al-Mg-Sc-Zr-Ni alloys prepared by vacuum induction melting in acidic chloride solution was studied. The morphological characteristics of the corroded specimens were examined by OM(optical microscopy), SEMand EDX techniques. The results indicated that the intergranular and exfoliation corrosion susceptibility dramatically depended on the Ni content. The Al-Mg-Sc-Zr alloy with 0 and 0.5 wt.% Ni were lightly susceptible to intergranular corrosion as the precipitation of Mg2Al3 phases presented at grain boundaries and the Al3Ni particles were finely dispersive. The intergranular corrosion was enhanced by the Al3Ni particles enrichment and became pitting corrosion with increasing Ni to 1.0 wt.%. Finally, the exfoliation corrosion happened to the alloy with 2.0wt.% Ni. This trend correlated well with the electrochemical property and distribution of Al3Ni phases. The corrosion potential of Al3Ni intermetallic phase is nobler than the β phase and the matrix, which result in an appearance of galvanic coupling. In addition, the increase of Al3Ni particles enlarged the attack area and the inhomogeneous segments of Al3Ni and Al3Mg2 phases accelerated the localized corrosion.

Quantitative study of exfoliation corrosion: Exfoliation of slices in humidity technique

A new technique, exfoliation of slices in humidity (ESH), was developed for the determination of exfoliation corrosion (EFC) susceptibility and quantification of EFC kinetics. Two AA7178 plates taken from the wingskin of a retired KC135 airplane were used as test samples. Slices of the plate were pretreated by potentiostatic polarization in chloride solution to develop localized corrosion sites. Subsequent exposure to high humidity after pretreatment of properly oriented and unconstrained samples resulted in the development of EFC at the edges of the slices. The EFC kinetics were determined by measuring the width of the central unattacked region of the samples. The ESH results were representative of the different EFC behavior of the two plates during outdoor exposure. These results show the capability of the ESH test to discriminate between plates of varying susceptibility and to determine EFC rates quantitatively. The different susceptibility of the two plates to EFC was attributed to differences in microstructure and grain boundary chemistry.

The influence of hot deformation on the exfoliation corrosion behaviour of aluminium alloy 2025

The influence of hot deformation and alloy composition on the tensile properties and exfoliation corrosion susceptibility of the aluminium alloy 2025 has been investigated. Five casts of 2025 were used to make extrusion billets. These were designated, low manganese, high manganese (with low copper), high chromium, high titanium and, outside the permitted range but reflecting more modern alloy design, high zirconium. Billets were then hot extruded and hot forged at a range of temperatures expected to produce unrecrystallised, partially recrystallised and fully recrystallised microstructures. The main objective of the compositional variation was to alter the wrought grain refining intermetallic phase. After the application of a standard heat-treatment, tensile properties were determined, and exfoliation tests were performed in accordance with ASTM-G34. The exfoliation susceptibility and mechanical properties of AA2025 showed a marked dependence on microstructure developed during hot forming and heat-treatment. Higher forming temperatures resulted in coarser recrystallised microstructures, which tended to reduce the susceptibility to exfoliation corrosion, but adversely affected tensile properties.