Evaluation of Conversion Coatings Without Hexavalent Chromium for Aerospace and Defense Applications
Conversion coatings containing hexavalent chromium are currently used in aerospace and defense manufacturing on various aluminum alloys to provide corrosion protection and enhanced adhesion of subsequent coatings. However, hexavalent chromium is toxic to humans with negative health effects from acu...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Instituto de Aeronáutica e Espaço (IAE)
2022-02-01
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| Series: | Journal of Aerospace Technology and Management |
| Subjects: | |
| Online Access: | https://www.scielo.br/j/jatm/a/XCGCDVKvgQTWHYZSPxxyXQz/?format=pdf&lang=en |
| Summary: | Conversion coatings containing hexavalent chromium are currently used in aerospace and defense manufacturing on various aluminum alloys to provide corrosion protection and enhanced adhesion of subsequent coatings. However, hexavalent chromium
is toxic to humans with negative health effects from acute and chronic exposure. Regulatory mandates have accelerated a global effort to replace hexavalent chromium-containing materials because of their toxicity. A consortium was established to evaluate
safer conversion coating materials, including the chemical processing of the surfaces prior to applying the conversion coatings. Four conversion coatings without hexavalent chromium were compared against a hexavalent chromium-based conversion coating
for the following tests: coating weight, electrical contact resistance, paint adhesion, bare and painted neutral salt fog corrosion tests, painted SO2 salt fog corrosion test, and painted outdoor beachfront corrosion test. The test results for the four conversion
coatings without hexavalent chromium were encouraging since several candidates exceeded some of the specification requirements or consortium expectations. In particular, the Socosurf TCS/PACS conversion coating performed well in the coating weight, electrical contact resistance, paint adhesion, and corrosion tests. The results of this evaluation provide significant progress toward providing a replacement material for a traditionally hexavalent chromium material application on aluminum.
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| ISSN: | 1984-9648 2175-9146 |