The Corrosion Inhibition Behavior of Thermally Aged Chromate Conversion Coating applied to Aerospace Aluminum 2219

Authors

Michelle Stephane PierreFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Materials Science and Engineering

First Advisor's Name

Dr. Norman Munroe

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Dr. Shekhar Bhansali

Second Advisor's Committee Title

Co-Committee Chair

Third Advisor's Name

Benjamin Boesl

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Kingsley Lau

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Chengxian Lin

Fifth Advisor's Committee Title

committee member

Sixth Advisor's Name

Eliza Montgomery

Sixth Advisor's Committee Title

committee member

Keywords

aluminum 2219, conversion coating, corrosion

Date of Defense

11-10-2021

Abstract

NASA Kennedy Space Center’s technical standard for corrosion protection of space flight hardware provides guidance concerning temperature restrictions and exposure limits for processing unpainted chromate conversion coatings (CCC) for the Orion crew space vehicle as part of the Artemis program. The standard requires that all CCC treated flight hardware components be fully coated within seven days with a maximum storage time of seven days at ambient temperatures (much less time at higher temperatures). Currently, there is no literature nor qualified industry testing supporting the exposure limits set by the standard. The standard is quite restrictive to processing flight components. In some cases, a conversion coating will be used without an additional coating to provide more limited corrosion protection while the flight hardware undergoes many different, but controlled, processes that are time consuming. The protective coatings need to maintain their integrity throughout processing, so understanding the corrosion mechanisms associated with the materials and corrosion control limitations is vital for the health of the spacecraft. In this study, CCC was applied to aerospace grade Aluminum 2219 samples that were aged for three months and then subsequently heat treated at 65°C and 129°C. This research focused on using surface-based characterization techniques to evaluate the corrosion resistance of the thermally aged CCC treated Al2219 panels via electrochemical analysis and exposure to standard salt-fog corrosion testing. Electrochemical studies monitored coating degradation with age at ambient laboratory conditions and at elevated temperatures. Surface chemistry techniques, XPS and SEM/EDS, were used to monitor progression of dehydration as samples aged and heat treated. The extent of pit density of the samples were evaluated based on age and heat treatment using three-dimensional optical profilometry. This study clarified some uncertainties regarding temperature and storage of CCC treated Al2219. Samples that were CCC treated and stored at ambient temperatures and samples that were heat treated to 65°C provided similar corrosion protection of Al2219 up to three months. The coatings that were heat treated to 129°C performed poorly despite age. It was evident that these samples underwent a gradual progression dehydration and loss of chromium hydroxides which provides a barrier of protection to the substrate.

Identifier

FIDC010474

ORCID

https://orcid.org/0000-0001-8940-2337

Recommended Citation

Pierre, Michelle Stephane, "The Corrosion Inhibition Behavior of Thermally Aged Chromate Conversion Coating applied to Aerospace Aluminum 2219" (2021). FIU Electronic Theses and Dissertations. 4887.
https://digitalcommons.fiu.edu/etd/4887