1. Why Study Corrosion 1 Sheldon W. Dean 12/7/02

2. What is Corrosion? What does it look like? How do you know when you have it?

3. What is Corrosion? Metals made by smelting ( reduction of ore) Metals in air want to return to their oxidized state Corrosion is a natural process!

5. Is Corrosion Important? National issue? International issue? What industries are affected? Does it affect us personally?

6. Importance to USA CC Technologies study – March 2002 In 2000 about 3.1% of GDP spent on corrosion repair and control Total cost $276Billion! Of industries analyzed, the cost was $137.9 Billion

8. Examples of Corrosion Damage Automotive problems - body rust Home examples- - Plumbing fixtures - Mail box - Exterior fixtures and fasteners Concrete cracking

9. Corrosion Affects Our Safety! Unexpected failures of equipment and devices Need to replace damaged items Corrosion weakens structures - Need to evaluate fitness for service when corrosion occurs

10. What Does Corrosion Look Like? Rust and tarnish, red blue or gray scale 8 types of damage – Fontana Several others also.

11. Most Common Forms of Corrosion General attack (uniform wastage) Pitting/ Crevice attack Cracking (embrittlement) Galvanic corrosion

12. Corrosion is Electrochemical Two different reactions occur - oxidation and reduction Electron transfer occurs Potential (voltage) driving force required Oxidation occurs at anode Reduction occurs at cathode

13. Corrosion Reactions Oxidation - e.g. Fe  Fe ++ + 2e Reduction – e.g. O 2 + 2H 2 O  4OH - - 4e Secondary - e.g. 4 Fe ++ + O 2  Fe 2 O 3 + 8H +

18. Conclusions Corrosion rate depends upon the corrosion products that form Solubility of corrosion products determines the rate If solubility is high, the rate is high! If solubility is low, the rate is low

20. Potential/pH (Pourbaix) Diagram Very useful way to present data Developed by Marcel Pourbaix (1966) Available for all metals and many other elements Shows solubility and potential effects If solubility is < 10 -6 M/l, no corrosion is assumed

21. Characteristics of Corrosion Products Very thin and dense: protective,e.g., Cr, Al, Ti, 10 to 100 nm thick Thin: protective but some corrosion occurs, e.g.,Cu, Zn, Pb 1 to 10  m Thick and porous, e.g., Fe, >100  m Corrosion is a problem. Soluble, e.g., Na, K Not able to be used.

22. Dealing with Corrosion There are many ways to prevent or minimize corrosion damage

23. Alloying to Resist Corrosion - Steel Add >13% Cr (stainless steel) Add >2% Mo to stainless (to resist pitting) Add Si, P, Cu, Cr ( and others) to obtain weathering steel

24. Alloying to Resist Corrosion - Copper Add Ni and Fe (cupronickel) sea water Add As, Sb, or P to prevent dealloying of brass (Cu + 10 to 35% Zn) Add Al or Si to resist erosion

25. Metallic Coatings Widely used to protect steel and to make other metals more attractive Zn and Zn alloys on steel – Galvanizing Ni + Cr on steel, brass or zinc to give a bright finish Cu + Ni + Cr also used for bright finish

26. Organic Coatings - Paint Barrier layer to keep water away Adhesion is key to success Susceptible to thermal damage Susceptible to UV damage

27. Electrochemical Protection Cathodic protection – reduce the potential and also corrosion rate - widely used underground and in sea water Anodic protection – increase potential to produce a less soluble corrosion product – used in some chemical plants

28. Corrosion Inhibitors Used in water systems: - Automotive cooling systems - Cooling towers - Boilers, especially high pressure steam Temporary preservatives for metals - Volatile corrosion inhibitors Paints and primers

29. Quiz Time! What is the most corrosive substance we can think of? Corrosion damage only causes metals to become thinner – True or False? How does corrosion affect me?

30. Answers! Water!!! False! Corrosion also causes cracking, pitting, staining, wedging in crevices, loss of electrical conductivity, and failure of components What is your answer?

31. Break Time

32. Why Study Corrosion - 2 Sheldon Dean 12/7/02

33. Careers in Corrosion Technician - Education High school diploma + interest in chemistry or technology Associates degree – possible night school - not required at entry level - Chemistry - Electrical technology - Materials science

34. Careers in Corrosion Technician-Work Lab technician - Chemistry laboratory - Materials laboratory - Materials or chemical company Field technician – civil engineering - Pipeline monitoring - Bridges, tunnels etc.

35. Careers in Corrosion Civil Engineer - Education Civil, mechanical or electrical SB MBA or MS (not required but often helpful) PE license NACE Certification

36. Careers in Corrosion Civil Engineer - Work Engineering firm or consultant - Cathodic protection design - System monitoring and evaluation State or local government - Specify protection systems for bridges, tunnels, other facilities - Inspection and monitoring

37. Mat., Chem., Chem. Eng. Education High School Diploma College SB, Major: Mat. Eng., Chem., Chem. Eng., or Mech.Eng. Grad school optional, MBA, MS or PhD Certification NACE (optional) PE License (optional)

38. Mat.,Chem.,Chem. Eng. Work Chemical, materials, petroleum, auto firm - Engineering - Safety - Research (PhD) - Plant Maintenance Engineering or consultant firm

39. NACE International Short courses, some with certification Annual meeting and show Standards development Local sections Symposia Books, videos and computer products

40. NACE International The Corrosion Society Address: P.O.Box218340, Houston,TX77218-8340 Phone: 281-228-6200 Website: www.nace.org

41. ASTM International Standards development, Vol.03.02 Training courses Symposia Address:100 Barr Harbor Drive, West Conshocken, PA 19428-2959 Website: www.astm.orgwww.astm.org Corrosion committee: G-1

42. Corrosion Testing Used for a variety of purposes Standard test methods available Some tests are simple and easy to run ASTM corrosion tests are in Volume 03.02 of the “Annual Book of ASTM Standards”

43. Corrosion Testing- Purposes Accelerated tests to demonstrate products durability Acceptance tests to show that a material meets standard Monitoring tests to show changes in a system corrosivity Research tests to determine mechanism of corrosion

44. Standard Tests Usually corrosion tests have many parameters Corrosion tests often give results that are difficult to reproduce – Standardization helps reproducibility Consensus standard tests: ASTM and NACE

45. Accelerated Test Example ASTM G48 Pitting and Crevice Corrosion Resistance Ferric chloride, 6%solution 72Hrs at 22 o C (room temperature) Report pitting or crevice corrosion Simulates sea water attack of stainless steels

48. Acceptance Test - Al Alloys ASTM G 69, Test of metallurgical condition of Al alloys Measure potential,E, in salt solution Cu increases E, Zn reduces E Heat treatment determines condition Condition affects strength and corrosion tendencies

49. ASTM G 69 Continued Solution: 1M Na Cl + 2.7%H 2 O 2, 22 o C Surface preparation: 00 steel wool rub 1 Hour immersion Measure potential every 5 minutes after 30 minutes against SCE electrode Average result: -750+/-10mV for pure Al Al foil is pure Al

51. Monitoring Test ASTM C 876 Corrosion of steel rebar in concrete Potential indicates when corrosion of steel is occurring Copper/copper sulfate reference cell Chloride causes steel to corrode Deicing salt usually reason for problem Sea water also causes problems

54. Procedure ASTM C876 Place electrode on concrete surface Measure potential with volt-meter If potential varies with time prewet surface with 25ml/l detergent solution Record potential at several points on the surface

55. Analyze Data Arrange values in ascending order and number the values sequentially Determine plotting position,f f = r/(n +1) where r is the measurement number, and n is the total number of values Plot on probability paper

57. ASTM C876 Report Potential > -0.20 V, rebar is not corroding Potential <-0.35V, rebar is corroding Potential in between then the rebar may be corroding

58. Demonstration of Corrosion A simple test to show local cathodes and anodes with a corroding specimen Uses indicators to show where reactions occur Phenolphthalein turns red at cathode (OH – ion generated there) K 3 Fe(CN) 6 turns blue at anode

59. Demonstration Test Materials Agar agar Salt (NaCl) 5%K 3 Fe(CN) 6 solution 1% Phenolphthalein solution (in alcohol) 2 steel nails, bright finish (e.g.: 10d) 1 steel nail, galvanized (e.g.:10d) Copper wires

60. Demonstration test Procedure Prepare 250 ml of 3%salt (7.5g) and 2% agar agar solution Boil to dissolve agar agar Add 5ml K 3 Fe(CN) 6 solution and 1ml of phenolphthalein solution Pour into 2 dishes, one with bright nail, one with bright nail wired to galvanized nail

61. Demonstration Test Procedure Continued Allow the solutions to cool and watch colors develop Where do are the red areas? (cathodes) Blue areas? (anodes) What does it mean when no blue areas develop on the bright nail wired to the galvanized nail?

64. Follow-up NACE Foundation NACE Foundation wants to help high schools with programs and information NACE local sections can provide technical people to run field trips or lead experimental demonstrations Contact Teri Elliott, phone 281-228- 6210 Website: www.nace.foundation.org

65. Summary Corrosion is an important issue Corrosion technology shows where chemistry can be used to prevent problems Corrosion tests can provide good hands-on experience for students Many opportunities for careers in corrosion prevention

67. Thank You! Questions please?