Corrosion Corner ello, everyone. Over the years, I’ve been asked a number of questions that fall into the Frequently Asked Questions (FAQ) category. I thought it would be interesting to answer the top six FAQs. Of course, each question has an overview answer and a more detailed answer—I’m going to provide the overview answers. FAQ 1: Is there a paper or book that would tell me all I need to know about spray package corrosion? The short answer is no. We have a primer that provides an overview for spray package corrosion, and you can obtain a copy by sending me an email. We also have our 1 ½ day short course on the Elements of Spray Package Corrosion that we teach at clients’ R&D facilities. FAQ 2: Where are the academic programs in corrosion engineering and science? There is no academic degree in corrosion. Typically, one writes a thesis or dissertation on a corrosion topic. You’ll find publications on corrosion from a wide range of academic disciplines, such as: FAQ 3: What is the spray package corrosion mechanism? There are many different types of spray package corrosion mechanisms. In very general terms there is liquid phase corrosion (corrosion in the liquid product) and a vapor phase corrosion. Liquid phase corrosion occurs in the bulk liquid (your formula) and could be general metal corrosion, sometimes referred to as uniform corrosion, metal pitting corrosion, metal crevice corrosion and coating delamination, such as blistering. 20 Spray August 2014 W. Stephen Tait, Ph.D. Chief Science Officer & Principal Consultant, Pair O Docs Professionals, LLC The top six FAQs about spray package corrosion H Vapor phase corrosion could also have one or more of the corrosion types found in the liquid phase. However, vapor phase corrosion occurs under a thin layer of water (approximately 30 microns 0.03mm thick). FAQ 4: How much water is needed for corrosion? Metal and polymer corrosion initiates only when liquid water is present. Thermodynamically, liquid water occurs when there is a conglomeration of 90 water molecules. However, the actual number of water molecules needed to form liquid water depends on the chemical composition of your formula and the type of spray package materials. Additional liquid water is needed to sustain corrosion after it initiates. The amount of water needed to sustain corrosion is determined by the type(s) of corrosion and the type(s) of packaging material. FAQ 5: What corrosion inhibitor works for most—if not all— spray package corrosion? No single corrosion inhibitor works for all situations. The chemical composition of your formula and types of materials used in your spray package determine whether an individual inhibitor or an inhibitor blend slows down package corrosion by your formula. FAQ 6: How long does a corrosion test need to last before making a commercial decision? It has been my experience that a storage test needs to be conducted for at least one year to reduce the corrosion risk between 2% and 7%. Please send your questions, comments and suggestions to rustdr@pairodocspro.com. Previous issues of Corrosion Corner are available on CD from SPRAY. Thank you for your interest and I’ll see you again in September. Spray • Chemistry • Polymer chemistry • Chemical engineering • Physics • Biology • Materials engineering • Mechanical engineering • Civil engineering • Electrical engineering • Mathematics and Statistics
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