Coatings and Surface Engineering for Environmental Protection II: Corrosion Control Session III
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Arif Mubarok, PPG; Raul Rebak, GE Global Research; Rajeev Gupta, North Carolina State University; Tushar Borkar, Cleveland State University; Brian Okerberg, PPG Industries; Michael Mayo, PPG Industries
Thursday 8:30 AM
February 27, 2020
Room: 19
Location: San Diego Convention Ctr
Session Chair: Brian Okerberg, PPG Industries; Rajeev Gupta, North Carolina State University
8:30 AM Invited
Microstructure and Electrochemistry of Al-Rich Primer: Shanshan Wang1; Xi Wang1; Siva Palani2; Alan Rose2; Gerald Frankel1; 1The Ohio State University; 2Corrdesa
Al-rich primer is designed to be anodic relative to high strength Al alloys, so that it drives the mixed potential of Al alloy substrates (e.g. AA2024) into the cathodic region below the breakdown potentials of the Al alloys, preventing localized corrosion. The Al-rich primer under study is composed of spherical TCP-treated Al-Zn-In pigments in an epoxy binder. The microstructure of the Al-rich primer was studied using a combination of XRM, SEM and TEM techniques. Polarization and EIS tests were conducted to measure the electrochemistry of the Al-Zn-In alloy under neat primer in NaCl solution to simulate the environment which Al-Zn-In pigments are exposed to in the real primer. Galvanic corrosion between the AA2024 substrate and Al-Zn-In bulk alloy was also studied using a ZRA.
8:50 AM Invited
The Effect of Surface Treatment on the Performance of a Zirconium-based Conversion Coating on AA7075 Automotive Alloys for Protection Against Filiform Corrosion: Carol Glover1; Mary Lyn Lim2; John Scully1; 1University of Virginia; 2PPG Industries
The resistance to filiform corrosion (FFC) of AA7075 automotive aluminum alloys, when pretreated with a Zirconium-based conversion coating, was investigated as a function of surface-treatment and heat-treatment. Specimens were prepared with two surface-treatments, (1) alkaline-cleaning and (2) alkaline-cleaning and subsequent acid deoxidation. These were compared to a control and studied with and without a pretreatment. Two different heat-treatments were applied to mimic curing temperatures. Data from FFC and full-immersion corrosion experiments are compared with surface characterization data to study the FFC kinetics and inhibition mechanism of the FFC process. The effect of surface-treatment and heat-treatment on intermetallic particle (IMP) density and surface enrichment of alloying elements is discussed. It was found that specimens prepared by alkaline cleaning-only provided superior resistance to FFC and this performance was shown to be least effected by the applied heat-treatments. A substantially thicker (60 nm) Zr-based oxide layer was shown to form on this specimen.
9:10 AM Invited
Improved Corrosion Resistance of a Commercial Mg Alloy through Laser Assisted Surface Processing: Saumyadeep Jana1; Zihua Zhu1; Mark Engelhard1; Danny Edwards1; Aashish Rohatgi1; Hongtao Ding2; 1Pacific Northwest National Laboratory; 2The University of Iowa
Mg alloys, because of its excellent strength to weight ratio, offer promising solutions for light weighting challenges encountered in various industrial sectors. However, wider use of Mg alloys is limited by poor corrosion resistance, especially in chloride containing environments. The present study shows the beneficial effect of laser shock processing (LSP) on corrosion behavior of a 1 mm thick commercial AZ31 sheet. During ASTM B117 test using 5% NaCl solution, the extent of corrosion attack on LSP-treated AZ31 coupons were found to be lower than the untreated base metal by at least one order of magnitude. The chemical composition and the microstructure of the LSP surface has been identified using advanced spectroscopy (SIMS, XPS) methods together with high resolution imaging (SEM, TEM). The mechanism responsible for improved corrosion behavior will be discussed on the basis of detailed microstructural characterization and electrochemical testing.
9:30 AM Invited
Towards Designing and Discovering Novel Corrosion Inhibitors for Solution and Coating Applications: Gavin Collis1; 1CSIRO Manufacturing
The corrosion of metals and alloys is an electrochemical process where in applications such as aviation, defence, automotive, structural, marine, oil and gas and mining the consequences of uncontrolled corrosion events can be catastrophic. Of these examples, the use of corrosion inhibitors in solutions or in coatings is a common, relatively simple and a cost-effective way to minimize corrosion events in many everyday applications.Over the last few decades some corrosion inhibitors have been deemed hazardous and as a result are being globally phased out from commercial use. Whilst the development of new corrosion inhibitors has primarily been empirical we have attempted to take a holistic approach towards the design of novel inhibitors for specific solution and coating applications. Here building on the success at CSIRO in materials discovery activities for drug discovery and organic electronics we present our efforts towards new corrosion inhibitor materials.
9:50 AM
Understanding the Impact of Pigment Selection on the Properties of Electrodeposited Coatings: Kevin Sylvester1; Corey DeDomenic1; Egle Puodziukynaite1; Fuduo Ma1; 1PPG Industries
Electrocoat has been an automotive industry standard for excellent corrosion performance for over fifty years. Modifications to resin design, to catalyst chemistry, and to pigment selection have resulted in the improvement of various performance properties. This seminar will discuss the impact of pigment to binder ratio (P/B) and pigment selection on electrocoat properties, including film appearance, throw power, and lower cure response.
10:10 AM Break
10:25 AM Invited
Phase-Field Modeling of Microstructural Effects on the Corrosion of Mg Alloys: David Montiel1; Stephen DeWitt1; Alexander Chadwick2; Katsuyo Thornton1; 1University of Michigan; 2Northwestern University
Understanding how alloy composition and thermal history determine the corrosion behavior is crucial to designing alloys with lower corrosion rates. We employ the phase-field and smoothed boundary methods to investigate the effect of microstructure on the corrosion behavior of Mg alloys. Starting from a microstructure representative of an alloy surface, we simulate the corrosion of the alloy when exposed to an electrolyte. By defining separate local corrosion reaction kinetics for each phase, we are able to examine how the exposed fractions of different precipitates affect the overall corrosion rate. Additionally, we study how the microstructural evolution is affected due to variations in reaction kinetics from the local depletion of solute near precipitates.
10:45 AM
Oxidation Behavior of TiAl Alloys and its Optimization by Deposition of Al-rich Coatings via Pack Aluminizing: Lukas Mengis1; Anke Ulrich1; Alexander Donchev1; Mathias Galetz1; 1DECHEMA Research Institute
Titanium aluminides are excellent light-weight materials for high-temperature applications, among others, because of their superb specific high-temperature strength. However, their application above 750°C is restricted by their insufficient oxidation resistance. In this regard, oxidation does not only lead to the formation of an unprotective mixed oxide scale but further aggravates the inherent brittleness of these intermetallics. This study undertakes a comparative investigation of the oxidation behavior of the TiAl alloys GE 48-2-2 and TNM-B1 at 600-900 °C for up to 1000 h in air. Emphasis is placed on the occurring oxidation mechanisms as well as related microstructural changes. A coating concept based on pack aluminizing is presented aiming to minimize the oxidation-induced embrittlement of the investigated alloys. Comparing four-point-bending tests as well as nanoindentation measurements of the coated and uncoated samples have been performed after exposure in air in order to verify the enhanced resistance against the embrittlement.
11:05 AM
Oxidation Behavior of Cold Spray Chromium Coatings on Zircaloy-4 in Steam Environments in 1100 °C to 1300 °C Temperature Range: Hwasung Yeom1; Benjamin Maier1; Greg Johnson1; Tyler Dabney1; Mia Lenling1; Kumar Sridharan1; 1University of Wisconsin Madison
The oxidation kinetics and microstructural evolution of Cr coating deposited on Zircaloy-4 using the powder-based cold spray process in temperature range of 1100 °C to 1300 °C are discussed. Tests were conducted in flowing steam at atmospheric pressure. The study aims understanding the oxidation behavior of these coatings under conditions pertinent to Design Basis Accidents and Beyond Design Basis Accidents in Light Water Reactors. Evolution of surface morphology, microstructure, and phases of the coated samples were characterized using scanning electron microscopy, x-ray diffraction, and transmission electron microscopy. The growth kinetics of Cr-oxide layers on the surface of the Cr coating and Cr/Zr interdiffusion layers at the coating/substrate interface were quantified. Nano-indentation tests were performed across coating/substrate interface to assess mechanical property changes after the high temperature exposure. It is expected the results could feed data to LWR system codes for better prediction of coping time in the event of accidents.