Phosphate-Doped Borosilicate Enamel Coating Used to Protect Reinforcing Steel from Corrosion
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Scholars' Mine Doctoral Dissertations Student Theses and Dissertations Fall 2014 Phosphate-doped borosilicate enamel coating used to protect reinforcing steel from corrosion Xiaoming Cheng Follow this and additional works at: https://scholarsmine.mst.edu/doctoral_dissertations Part of the Materials Science and Engineering Commons Department: Materials Science and Engineering Recommended Citation Cheng, Xiaoming, "Phosphate-doped borosilicate enamel coating used to protect reinforcing steel from corrosion" (2014). Doctoral Dissertations. 2339. https://scholarsmine.mst.edu/doctoral_dissertations/2339 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. 2 PHOSPHATE-DOPED BOROSILICATE ENAMEL COATING USED TO PROTECT REINFORCING STEEL FROM CORROSION by XIAOMING CHENG A DISSERTATION Presented to the Faculty of the Graduate School of the MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY in MATERIALS SCIENCE AND ENGINEERING 2014 Approved by: Richard K. Brow, Advisor Genda Chen Delbert E. Day Matthew J. O’Keefe Mark E. Schlesinger 3 2014 XIAOMING CHENG All Rights Reserved iii PUBLICATION DISSERTATION OPTION This dissertation consists of a section of introduction, four papers and a section of appendix. Papers I (pages 20-57) will be submitted for publication in the Journal of Non- Crystalline Solids. Papers II (pages 58-88) will be submitted for publication in the Journal of Non- Crystalline Solids. Papers III (pages 89-120) will be submitted for publication in the Journal of Non- Crystalline Solids. Paper IV (pages 121-152) will be submitted for publication in the Journal of Surface and Coatings Technology. The appendix includes one paper in the form of manuscript and will be modified and expanded before submitting for publication in the Journal of Non-crystalline Solids. iv ABSTRACT Phosphate-doped sodium borosilicate glasses were developed for enamel coatings to provide corrosion protection for reinforcing steel in concrete. Phosphates have low solubilities in borosilicate glasses, generally less than about 4 mol%, and are incorporated 3- 4- mainly as isolated PO4 and P2O7 anions, along with some borophosphate bonds. With the addition of P2O5, the silicate network is repolymerized and tetrahedral borates are converted to trigonal borates, because the phosphate anions scavenge sodium ions from the borosilicate network. The addition of Al2O3 significantly increases the solubility of P2O5 due to the formation of aluminophosphate species that increases the connectivity of phosphate sites to the borosilicate glass network. The addition of P2O5 has an insignificant effect on thermal properties like Tg, Ts and CTE, and chemical durability in alkaline environments can be improved, particularly for glasses co-doped with alumina. When the solubility limit is reached, a phase-separated microstructure forms, degrading the chemical durability of the glass because of the dissolution of a less durable alkali borate phase. The dissolution rates of glasses in a simulated cement pore water solution are orders of magnitude slower than in Ca-free solutions with similar pH. In Ca-saturated solutions, a passivating layer of calcium silicate hydrate (C-S-H) forms on the glass surface. Phosphate-rich glasses react with the simulated cement pore water to form crystalline hydroxyapatite (HAp) on the glass surface. Electrochemical tests reveal that the HAp precipitates that form on the surfaces of intentionally-damaged phosphate-doped enamel coatings on reinforcing steel suppress corrosion. The enhanced corrosion protection is retained in chloride-containing pore water, where the development of hydroxyl-chlorapatites immobilizes the free chloride ions in solution. v ACKNOWLEDGMENTS I appreciated the opportunity to participate in the enamel coating project developed as a collaboration between the Civil, Architectural and Environmental Engineering Department and the Materials Science and Engineering Department at Missouri S & T. The project was funded by the National Science Foundation (CMMI- 0900159). My deepest appreciation goes to my advisor, Dr. Richard Brow. The luckiest thing I ever had over the last couple of years is the opportunity to have Dr. Brow as my Ph.D advisor. During these years working with him, I have learned great many things both personally and professionally from him. Although I had a fairly long learning curve in the beginning since I did not have a background in glass science, Dr. Brow was always there to help me with whatever I needed. I am afraid that I just contributed more grey hair to him, but from my point of view, it has worked out well. I would also like to thank my committee members, Dr. Genda Chen, Dr. Delbert E. Day, Dr. Matthew J. O’Keefe, Dr. Mark E. Schlesinger for their guidance and help during the course of this work. I also appreciate the generous use of equipment in Dr. O’Keefe’s and Dr. Chen’s labs. Many Scientists and technicians, at Missouri S & T and elsewhere, also helped me a lot in this work. Dr. Sarah Cady, Dr. Christian Bischoff and Ms. Deborah Watson at Iowa State University provided solid-state NMR and Raman analysis. Technicians in MRC have helped me in many ways. I also appreciate the great help from Dr. Fujian Tang, Dr. Surender Maddela and Dr. James Claypool for teaching me the electrochemical tests and analyses. I also thank the students in Dr. Chen’s group and Michael Koenigstern (Pro-Perma Engineered Coatings) for many helpful discussions. I appreciate the help and friendship from my group members: Kathryn Goetschius, Jaime George, Lina Ma, Charmayne Smith, Jen-Hsien Hsu and many previous members. Thank you all for the time we spent together for work or play. Last but not least, I would like to thank my parents, my sister and my brother for their love and support throughout these years. vi TABLE OF CONTENTS Page PUBLICATION DISSERTATION OPTION ................................................................... iii ABSTRACT ....................................................................................................................... iv ACKNOWLEDGMENTS .................................................................................................. v LIST OF ILLUSTRATIONS ............................................................................................ xii LIST OF TABLES ......................................................................................................... xviii SECTION 1. PURPOSE OF THIS DISSERTATION ..................................................................... 1 2. INTRODUCTION ...................................................................................................... 2 2.1. BACKGROUND ................................................................................................ 2 2.1.1. Reinforcement Corrosion in Concrete Structure. ..................................... 2 2.1.2. Corrosion Prevention by Protective Coatings. ......................................... 4 2.2. INTERACTIONS OF BOROSILICATE GLASS WITH CEMENTITIOUS MATERIALS ..................................................................................................... 6 2.3. STRUCTURE OF PHOSPHATE-DOPED BOROSILICATE GLASS ........... 11 2.4. PROPERTIES OF PHOSPHATE-DOPED BOROSILICATE GLASS .......... 14 2.4.1. Phosphate Induced Phase Separation in Borosilicate Glass. .................. 14 2.4.2. Effect of P2O5 on the Properties of Homogeneous Borosilicate Glass. 14 2.5. CORROSION RESISTANCE OF ENAMEL COATINGS ............................. 16 2.6. RESEARCH OBJECTIVE ............................................................................... 18 vii PAPER I. EFFECT OF P2O5 IN SODIUM BOROSILICATE AND ALUMINOBOROSILICATE GLASSES ON STRUCTURE: MULTI-NUCLEAR (31P, 27Al, 11B, 29Si) MAS NMR AND RAMAN STUDY ............................................... 20 ABSTRACT ................................................................................................................. 20 1. Introduction .............................................................................................................. 21 2. Experimental procedures .......................................................................................... 22 3. Results ...................................................................................................................... 23 3.1. Raman Spectra .................................................................................................. 23 3.2. 31P MAS NMR Spectra ..................................................................................... 24 3.3. 27Al MAS NMR Spectra ................................................................................... 25 3.4. 11B and 29Si MAS NMR Spectra ....................................................................... 25 4. Discussion ................................................................................................................ 26 4.1. Spectra assignments .......................................................................................... 26 4.1.1. Raman band assignment ......................................................................... 26 4.1.2. NMR peak assignments .........................................................................