UNIVERSITY OF CALIFORNIA Los Angeles Aqueous Degradation of Materials: Studies on Steel Corrosion and Acoustically Stimulated Mineral Dissolution A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Materials Science and Engineering By Shiqi Dong 2020 © Copyright by Shiqi Dong 2020 ABSTRACT OF THE DISSERTATION Aqueous Degradation of Materials: Studies on Steel Corrosion and Acoustically Stimulated Mineral Dissolution By Shiqi Dong Doctor of Philosophy in Materials Science and Engineering University of California, Los Angeles, 2020 Professor Gaurav Sant, Co-Chair Professor Mathieu Bauchy, Co-Chair This work probed the two types of solid degradation in aqueous environment: steel corrosion, and acoustically stimulated mineral dissolution. First, the steel corrosions in gas/oil wells and nuclear power plant environment were studied. The inhibition of corrosion of API-P110 steel by Ca(NO3)2 was first studied using vertical scanning interferometry (VSI) in halide-enriched solutions. The results indicate that, at low concentrations, Ca(NO3)2 successfully inhibited steel corrosion in the presence of both CaCl2 and CaBr2. Statistical analysis of surface topography data reveals that such inhibition results from suppression of corrosion at fast corroding pitting sites. Built on the methodology established from above, the effect of grain orientation on the corrosion rates of austenitic AISI 316L stainless steel was studied. The oxidation rates follow a scaling that is given by: {001} < {101} < {111} for grains undergoing both active and transpassive oxidation. The corrosion ii tendencies of {001} and {101} grains indicate that the activation energy of dissolution follows a scaling similar to that of the surface energy. However, the high corrosion rates of {111} grains, which featured a surface energy lower than those of the {001} and {101} grains, is attributed to their lower tendency to adsorb passivating species, from solution, that leads to a net reduction in the activation energy of oxidation. Second, this work further investigated the low-temperature pathway of aqueous activation of minerals and industrial alkaline wastes using acoustic stimulation, as an alternative to calcination process in cement production. It is revealed that the acoustic fields enhance mineral dissolution rates (reactivity) by inducing atomic dislocations and/or atomic-bond rupture. The relative contributions of these mechanisms depend on the mineral’s underlying mechanical properties. Based on this new understanding, a unifying model was created that comprehensively describes how cavitation and acoustic stimulation processes affect mineral dissolution rates. On the basis of the mechanisms described above, the effectiveness and efficiency of applying acoustic stimulation in dissolving industrial alkaline wastes were further analyzed. Ultrasonication promoted dissolution of air-cooled blast furnace slag (ACBFS) in a significant and more energy-efficient manner, compared to traditional methods, such as grinding the solute, heating, and/or convectively mixing the solvent. The advantages of acoustic stimulation for dissolution enhancement and for energy savings are also observed for Si release from stainless steel slag (SSS), Class C fly ash, and Class F fly ash. The results demonstrate the wide applicability of acoustic processing, and the outcomes offer new insights into additive-free pathways that enable waste utilization, circularity, and efficient resource extraction from industrial wastes that are produced in abundance globally. iii The results yielded from this work provide enhanced understanding of corrosion inhibition and suggest processing pathways for improving the oxidation resistance of steels in different industry scenarios. In addition, the results provide insights of additive-free pathway by using acoustic stimulation to enable fast elemental extraction from mineral species into aqueous solution. iv The dissertation of Shiqi Dong is approved. Dwight Christopher Streit Jaime Marian Mathieu Bauchy, Committee Co-Chair Gaurav Sant, Committee Co-Chair University of California, Los Angeles 2020 v To my family, for their love, and endless support. vi TABLE OF CONTENTS Chapter 1. Introduction ................................................................................................................... 1 1.1 Background and Motivation ................................................................................................. 1 1.2 Steels and Steel Corrosion .................................................................................................... 3 1.2.1 Materials selection ......................................................................................................... 3 1.2.2 Steel corrosion ............................................................................................................... 5 1.2.3 Steel corrosion inhibition ............................................................................................. 10 1.3 Minerals and Mineral Dissolution ...................................................................................... 12 1.3.1 Materials selection ....................................................................................................... 12 1.3.2 Dissolution of minerals ................................................................................................ 15 1.3.3 Dissolution enhancement induced by acoustic stimulation ......................................... 20 1.4 Topographical Analysis Using Vertical Scanning Interferometry (VSI) ........................... 21 1.4.1 Basics of vertical scanning interferometry .................................................................. 21 1.4.2 Sample preparation and workflow for topography measurement ................................ 24 1.4.3 Topographical image processing and data analysis ..................................................... 26 1.5 Organization ........................................................................................................................ 27 Chapter 2. Steel Corrosion Inhibition by Calcium Nitrate ........................................................... 30 2.1 Introduction and Background ............................................................................................. 30 2.2 Materials and Methods ........................................................................................................ 31 2.2.1 Materials: Preparation of steel surfaces and brines ...................................................... 31 vii 2.2.2 Methods........................................................................................................................ 33 2.3 Results and Discussion ....................................................................................................... 36 2.3.1 Corrosion inhibition by calcium nitrate in the presence of halide-containing brines .. 36 2.3.2 The mechanism of corrosion inhibition by Ca(NO3)2 is revealed by statistical analysis of surface height evolutions and microstructural observations ............................................. 41 2.4 Summary and Conclusions ................................................................................................. 52 Chapter 3. Elucidating the Grain-orientation Dependent Corrosion Rates of Austenitic Stainless Steels ............................................................................................................................................. 54 3.1 Introduction and Background ............................................................................................. 54 3.2 Materials and Methods ........................................................................................................ 56 3.2.1 Sample preparation ...................................................................................................... 56 3.2.2 Crystallographic analysis ............................................................................................. 56 3.2.3 Oxidation (corrosion) rate analysis .............................................................................. 57 3.2.4 Data analysis workflow................................................................................................ 58 3.3 Results and Discussion ....................................................................................................... 59 3.3.1 Grain orientation impacts on the potential-free active corrosion of 316L ................... 59 3.3.2 Grain orientation impacts on the potential-induced transpassive corrosion of 316L .. 67 3.3.3 Correlating corrosion rates with grain orientations ..................................................... 67 3.3.4 Effects of surface and activation energies on corrosion rates ...................................... 70 3.4 Summary and Conclusions ................................................................................................. 73 viii Chapter 4. Atomic Dislocations and Bond-rupture Govern Dissolution Enhancement under Acoustic Stimulation ..................................................................................................................... 75 4.1 Introduction and Background ............................................................................................. 75 4.2 Materials and Methods ........................................................................................................ 77 4.2.1 Materials .....................................................................................................................