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Surface Treatment To Mitigate Exfoliation Corrosion Of 5XXX Series Aluminum Alloys

Product Number: 51321-16865-SG
Author: Ganesh Kumar Arumugam; Venkat Kamavaram; Reza Shahbazian-Yassar; Andrea Mansfeld; Vinod Veedu
Publication Date: 2021
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The United States Navy has an urgent need for fast, light-weight ships, such as the Littoral Combat
Ship (LCS), which uses strong, ductile, and corrosion-resistant aluminum alloys, AA5083 (UNS
A95083) or AA5XXX alloys. Magnesium rich AA5XXX series are susceptible to sensitization that
potentially leads to exfoliation (EC) and intergranular corrosion (IGC) when operating conditions exceed
50°C. In order to mitigate exfoliation corrosion, Oceanit has developed and demonstrated an innovative
surface treatment approach. A proprietary nanocomposite material was used that resulted in a low
energy surface with water contact angle >100 and inert to extreme corrosive chemicals and high
temperatures. Through ASTM G66 and B117, testing it was clearly demonstrated that untreated
samples exhibited high surface pitting and exfoliated edges whereas the nanocomposite treated
sample was near pristine. Microstructural analysis revealed that secondary phase precipitates that are
formed and migrated to grain-boundaries on untreated samples, whereas treated samples showed
negligible secondary phase precipitates. Based on microscopy and ASTM G66 test results, Oceanit
concludes that the nanocomposite treatment offers significant protection in corrosive environments and
reduces susceptibility for exfoliation.

The United States Navy has an urgent need for fast, light-weight ships, such as the Littoral Combat
Ship (LCS), which uses strong, ductile, and corrosion-resistant aluminum alloys, AA5083 (UNS
A95083) or AA5XXX alloys. Magnesium rich AA5XXX series are susceptible to sensitization that
potentially leads to exfoliation (EC) and intergranular corrosion (IGC) when operating conditions exceed
50°C. In order to mitigate exfoliation corrosion, Oceanit has developed and demonstrated an innovative
surface treatment approach. A proprietary nanocomposite material was used that resulted in a low
energy surface with water contact angle >100 and inert to extreme corrosive chemicals and high
temperatures. Through ASTM G66 and B117, testing it was clearly demonstrated that untreated
samples exhibited high surface pitting and exfoliated edges whereas the nanocomposite treated
sample was near pristine. Microstructural analysis revealed that secondary phase precipitates that are
formed and migrated to grain-boundaries on untreated samples, whereas treated samples showed
negligible secondary phase precipitates. Based on microscopy and ASTM G66 test results, Oceanit
concludes that the nanocomposite treatment offers significant protection in corrosive environments and
reduces susceptibility for exfoliation.