logging in or signing up CORROSION TEACHING. aSGuest118915 Download Post to : URL : Related Presentations : Let's Connect Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Copy embed code: Embed: Flash iPad Dynamic Copy Does not support media & animations Automatically changes to Flash or non-Flash embed WordPress Embed Customize Embed URL: Copy Thumbnail: Copy The presentation is successfully added In Your Favorites. Views: 280 Category: Science & Tech.. License: All Rights Reserved Like it (0) Dislike it (0) Added: November 09, 2011 This Presentation is Public Favorites: 0 Presentation Description A simple view on a complex matter Comments Posting comment... Premium member Presentation Transcript CORROSION “ A Simple view on a complex matter”: CORROSION “ A Simple view on a complex matter” J.Saranya Asst professor in Chemistry Department of S & HDefinition of Corrosion: Definition of Corrosion “ The process of decay of metal by environmental attack” Metals exposed to atmospheric gases, water and liquid medium. Converted to their ores. Eg: Rusting of ironSlide 3: Effects of corrosion Reduced Strength Life time is reduced Metallic properties are lost Wastage of metalTheories of Corrosion: Theories of Corrosion 1. Dry or Chemical corrosion Metal exposed to atmospheric gases in the absence of moisture Mechanism: Corrosion by Oxygen (Metal) M M n+ + n e - n e - + O 2 n O 2- M n+ + n O 2- nMO (Metal Oxide)Slide 5: Al, Pb, Cu, Cr, etc. form stable oxide layer Li, Ca, Na, K, etc. form unstable oxide layer Mo, Sn, etc. form volatile oxide layer Pt, Au, Ag – no corrosion Corrosion by Chlorine: Ag + Cl 2 2AgCl (ppt)Wet or Electrochemical corrosion: Wet or Electrochemical corrosion Liquid is in contact with a metal (b) Dissimilar metals or alloys are immersed partially or completely in a solutionSlide 7: Eg: Fe Fe 2+ + 2e - In acidic solution: 2H + + 2e - H 2 In basic solution: O 2 + 2H 2 O + 4e - 4OH - Fe 2+ + 4OH - 2Fe(OH) 2 In neutral solution: 2H 2 O + 2e - 2OH - Fe 2+ + 2OH - Fe(OH) 2Anodic & Cathodic Reactions: Anodic & Cathodic ReactionsSlide 9: Differential aeration corrosion: Metal is partially dipped in a solution less aerated area – corosion Eg: Wire mesh Accumulation of dirt, sand, scale, etc. Pitting corrosion: Surface roughness, scratches, stresses, etc.Slide 10: Caustic Embrittlement: Na 2 CO 3 + H 2 O 2NaOH + CO 2 2NaOH + Fe Na 2 FeO 2 Na 2 FeO 2 + H 2 O + O 2 12NaOH + 2Fe 3 O 4Factors influencing corrosion: Factors influencing corrosion Nature of metal: (a) Purity (b) Surface film (c) Volatility of the corrosion product (d) Solubility of the corrosion productSlide 12: 2. Nature of Environment: (a) Temperature (b) Humidity (c) Impurities (d) pHCorrosion control methods: Corrosion control methods Proper design Selection of metals Modifying the environment Sacrificial anodic protection Corrosion inhibitors Surface coatings (Paints, Electroplating, etc.)THANK YOU: THANK YOU You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.