The corrosion inhibition of aluminium alloy 7075-T651 with cerium and Mischmetal di phenyl phosphate

F. Varela, J. Hill, T. Markley, M. Forsyth, N. Birbilis, P. Howlett, B. Hinton

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Abstract

Previous studies have shown that cerium diphenyl phosphate (Cedpp) 3 is a very effective inhibitor of corrosion of aluminium alloys in chloride solutions. This paper describes the results of further studies using electrochemical and constant immersion corrosion tests to compare the effectiveness of Ce(dpp) 3 and Mischmetal diphenyl phosphate Mm(dpp) 3 as inhibitors of corrosion pitting on AA7075-T651 aluminium alloy. The results shows that both Ce(dpp) 3 and Mm(dpp) 3 are excellent inhibitors of pitting corrosion of this alloy in very aggressive environments of continuously aerated 0.1M and 1.0M sodium chloride (NaCl) solutions. Polarisation tests indicate that these compounds act as a cathodic inhibitors by reducing the rate of the oxygen reduction reaction, which results in a decreased corrosion current density and a separation of the corrosion potential from the pitting potential. This inhibition is thought to be due to the formation of a surface film consisting of rare earth metal oxide, aluminium oxide and a cerium-aluminium organo-phosphate complex. Surface analysis data from scanning electron microscopy and X-ray Energy Dispersive Spectroscopy show the complex nature of this protective film. This work further develops our understanding about the mechanisms through which these complex films form, and how inhibition occurs in the presence of these compounds.

Original languageEnglish
Title of host publication18th International Corrosion Congress 2011
Subtitle of host publication20-24 November 2011; Perth, Australia
Place of PublicationBlackburn VIC Australia
PublisherAustralasian Corrosion Association
Pages1787-1795
Number of pages9
Volume3
ISBN (Print)9781618393630
Publication statusPublished - 2011
EventInternational Corrosion Congress 2011 - Perth Convention and Exhibition Centre, Perth, Australia
Duration: 20 Nov 201124 Nov 2011
Conference number: 18th

Conference

ConferenceInternational Corrosion Congress 2011
Abbreviated titleICC 2011
CountryAustralia
CityPerth
Period20/11/1124/11/11
OtherThe 18th International Corrosion Congress took place between the 20th and the 24th November 2011 in the Perth Convention and Exhibition Centre, Australia. The International Corrosion Congress is the major event of the International Corrosion Council (ICC), an international body founded to advance corrosion science and engineering and is held once every three years by different host countries.

Keywords

  • Corrosion inhibition
  • Corrosion pitting

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