Coatings and Surface Engineering for Environmental Protection III: Protection from Environmental Degradation, Session I
Sponsored by: TMS Structural Materials Division, TMS Materials Processing and Manufacturing Division, TMS: Surface Engineering Committee, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Arif Mubarok, PPG; Tushar Borkar, Cleveland State University; Rajeev Gupta, North Carolina State University; Mary Lyn Lim, PPG Industries; Raul Rebak, GE Global Research; Brian Okerberg, PPG Industries

Monday 8:30 AM
March 15, 2021
Room: RM 18
Location: TMS2021 Virtual


8:30 AM  
Revealing the Long-term Growth Kinetics and Morphology of Atmospheric Corrosion Pitting in Aluminum via In-operando Microtomography: Philip Noell1; Michael Melia1; Eric Schindelholz2; 1Sandia National Laboratories; 2The Ohio State University
    Understanding the mechanistic relationship between the environment, microstructure, and local kinetics of atmospheric corrosion damage remains a central challenge. To address this challenge, this study used laboratory-based x-ray tomography to directly observe attack in-operando over an extended period, enabling the first observations of how the growth kinetics and morphology of individual pits evolve over months of exposure. Damage evolution associated with nine pits in a 99.9% pure aluminum wire exposed to chloride salts in humid air was studied over months of exposure. Most pits grew at a nominally linear rate up until pit death. Exceptions to this were observed, with three pits exhibiting bimodal growth kinetics. This was explained by secondary droplets that formed near the pits, increasing the cathode area. A corrosion-driven drying mechanism appears to lead to pit death in both cases. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

8:50 AM  
Pitting Corrosion in Powder-processed Aluminum Alloys Containing Quasicrystalline Dispersoids: Sarshad Rommel1; Hannah Leonard1; Mingxuan Li1; Thomas Watson2; Tod Policandriotes3; Mark Aindow1; 1University of Connecticut; 2Pratt & Whitney; 3Collins Aerospace
    Recently, we have developed a series of Al-Cr-Mn-Co-Zr alloys that exhibit a nano-composite FCC Al matrix plus quasicrystalline I-phase dispersoid microstructure in gas-atomized powders. The powder microstructures are retained during their consolidation to form bulk materials, but are altered significantly during upset forging of the consolidated bulk alloys. The pitting corrosion behavior of the alloys in Cl- rich environments has been studied using a combination of scanning and transmission electron microscopy, X-ray diffraction, and electrochemical techniques including electrochemical impedance spectroscopy, potentiostatic polarization and cyclic voltammetry. By comparing data obtained from the as-consolidated and the upset-forged alloys, we have elucidated the effects of the volume fraction and distribution of the reinforcement I-phase and the character of the surface corrosion product layers on the pitting corrosion resistance of these alloys.

9:10 AM  
The Effect of Surface Treatment on the Formation, Structure, and Chemistry of Protective Oxide Scale on High-temperature Oxidation-resistant Nickel Alloys: Stephen House1; Henry Ayoola1; John Lyons1; Meng Li1; Bingtao Li1; Judith Yang1; Wissam Saidi1; Brian Gleeson1; 1University of Pittsburgh
    High-temperature oxidation-resistant alloys often have finishes – such as polishing or vapor-blasting – applied to their exposed surfaces for aesthetic or practical reasons, which introduce deformation into the surface grain structure. Upon heating, a region of recrystallized grain structure can form at the surface. The degree and depth of the recrystallized zone depends on the type of surface finishing treatment, which in turn affects the extent of imposed surface deformation. Haynes 214® is a high-temperature oxidation-resistant nickel-aluminum-chromium-iron alloy that is known to form adherent alumina scales above 955 °C. Below this temperature, however, it can form either an alumina, chromia, or a combined oxide scale. In this work we employed surface (SEM, AFM) and subsurface (S/TEM, FIB) imaging and spectroscopic techniques to investigate the effect of various surface finishes on oxide scale formation and the surface and subsurface structure of the alloy resulting from the deformation and high-temperature oxidation processes.

9:30 AM  
Cycling Corrosion Testing of Al-Mg Friction Stir Welding Bi-metallic Joints: Qingli Ding1; Brajendra Mishra1; Adam C Powell1; Kübra Karayagiz1; 1Worcester Polytechnic Institute
    Friction Stir Welding (FSW) is now being used widely in designing vehicle parts. The next generation FSW Magnesium-Aluminum Vehicle Joints are up to 50% lighter than steel-based alloy, which can be much more energy saving. While the biggest challenge of FSW MG-AL Alloy is the galvanic corrosion between dissimilar metals. Cyclic Corrosion Test (CCT), based on the SAE J2334 standard, provides a more realistic exposure method to observe the corrosion change between them. Linear polarization resistance (LPR) as well as galvanic corrosion tests (ASTM-G71) will be used qualitatively to compare with the result of CCT. Scanning Electron Microscopy (SEM-EDS) will also be used to characterize the surface transformation.

9:50 AM  
Dealloying and Passivation of Cu-doped Carbide-reinforced Martensitic Steels in a Sulfuric Acid: Kenta Yamanaka1; Manami Mori2; Kazuo Yoshida1; Kazuyo Omura1; Yusuke Onuki3; Shigeo Sato3; Akihiko Chiba1; 1Tohoku University; 2National Institute of Technology, Sendai College; 3Ibaraki University
    High-speed steels, which consist of a martensitic matrix and numerous carbide precipitates, have been used as die and tool materials, because of their high hardness and excellent wear resistance. However, the corrosion resistance of such steels are generally not sufficient for specific applications . In the previous study, we developed Cu-doped Fe-Cr-W-C-based martensitic steels and demonstrated high hardness and excellent corrosion resistance simultaneously. Here, to understand the corrosion mechanism of the developed steel, the dealloying behavior at the surface of the steel in a sulfuric acid solution was investigated. The bulk Cr contents and higher quenching temperature increased the Cr contents in the martensitic matrix, decreasing the corrosion rate. Nonetheless, the enhanced corrosion resistance was associated with an accelerated dissolution of Cr2O3 film, which created the protective Cu-enriched layer and Fe2O3 phase at the surface. The relationship between the surface state and bulk microstructure of the steels is also discussed.