1. 1 Novel classes of organic corrosion inhibitors Dr. S. U. Rahman Associate Professor, Chemical Engineering Department King Fahd University of Petroleum & Minerals, Dhahran-31261, Saudi Arabia

2. 2 Applications of Corrosion Inhibitors  Water Potable Water  Silicates, Popyphosphates, CaCO 3 Cooling Water  Chromate, Nitrate, Polyphosphates, Automotive Coolants  Nitrite, Benzoate, Borax, Steam Condensates  Mophines, cyclohexamine, Long chain aliphatic amines Brine and Seawater  Nitrite, Chromates, Phosphates  Acid Pickling  Sulfur and nitrogen containing organic compounds  Oil Production and Refining  Sulfur and nitrogen containing organic compounds

3. 3 Factors Affecting Inhibition of Cooling Systems  Oxygen saturation  Water soluble gases  pH  TDS  Silt and solids  Sulfate bearing bacteria

4. 4 Requirements of Inhibitors  Surface coverage  Low concentration  Wide range of conditions (T, pH and water quality)  Should not produce solid deposits  Low/nil toxicity  Antiscaling properties

5. 5 Organic Inhibitors (Literature)  Mechanism Adsorb (chemisorb) to form barrier Coordinate covalent bond between metal and inhibitor React with environment to form thin coating  Bond strength depends on  Density of one pair or  electrons  Polarizibility of the functional group  Contain O, S or N  Mostly surfactant-like compounds  Contain polar head and nonpolar chain  Polar head helps in adsorption and impart solubility  Nonpolar chain provides the required coverage

6. 6 New Classes of Inhibitors  Following N containing compounds were studied Isoxazolidines 1 Cyclic Hydroxylamines 2 Cyclic Nitrones 3  Some of these compounds were synthesized first time  None of them have been tested as corrosion inhibitors 1 Ali, Saeed,, Rahman, Corrosion Science, 45 (2003) 253-266. 2 Saeed, Ali, Rahman, Anti-Corrosion Methods and Materials, 50 (2003) 201-207. 3 Rahman, Saeed, Ali, Anti-Corrosion Methods and Materials (Accepted).

7. 7 Isoxazolidines Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266.

8. 8 Isoxazolidines 1 Nitrone isoxazoidines Cycloadducts Diadducts 1 Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266.

9. 9 Quaternary Ammonium Salts 1 1 Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266. Isoxazolidine Quaternary Amm. Salt

10. 10 Summary of all isoxazolidines isoxazoidines Diadducts Cycloadducts Quaternary Ammonium Salts 1 Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266.

11. 11 Gravimetric Tests (Inhibition Efficiencies) Compoun d 50 ppm100 ppm200ppm400ppm 3a 40.753.673.886.7 3b 34.750.070.887.3 3c98.098.298.5 3d97.598.098.698.8 5a97.097.298.598.8 b 5b95.295.796.098.3 7a a 81.982.383.488.1 7b 8.6046.488.793.5 893.997.398.399.1 996.098.0 99.099.5 a soluble in 10% acetone in 1N HCl b %IE for 10 and 25 ppm were 87.2 and 91.8, respectively. Substrate metal : Mild steel, Temperature : 60 C, Exposure : 6 hrs, Base solution : 1 N HCl

12. 12 Isotherms  Isotherms provide insight into adsorption process  Surface coverage () can be evaluated as inhibition efficiency.  Langmuir Isotherm /(1- )=aC  Tempkin Isotherm =(1/f)log(aC)

13. 13 Isotherms of compounds 3a and 3b

14. 14 Tafel Tests Solution  corr, V SCE  a,, V/decade  C V/decade I corr (mA/cm 2 ) CR (mpy) Inhibition Efficiency Blank - 0.4800.17770.18132.25631031.8 0 3c - 0.4910.09760.13250.1057 48.3 95.32 3d - 0.4790.13300.12690.2255 103.1 90.01 5a - 0.4750.09700.11700.1794 82.0 92.05 8 - 0.4630.08670.12100.1107 50.6 95.10 Substrate metal : Mild steel, Temperature : 60 C, Exposure : 20 minutes, Base solution : 1 N HCl, Inhibitor Concentration : 400 ppm 1 Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266.

15. 15 Cyclic Hydroxylamines Saeed, M. T., Ali, A. A., Rahman, S. U., Anti-Corrosion Methods and Materials, 50 (2003) 201-207.

16. 16 Cyclic Hydroxylamines 2 Hydroxypyrrolidine Nitrone 1 Saeed, M. T., Ali, A. A., Rahman, S. U., Anti-Corrosion Methods and Materials, 50 (2003) 201-207. Hydroxylamines Cyclic Nitrones Hydroxylamines

17. 17 Hydroxylamines 1 Saeed, M. T., Ali, A. A., Rahman, S. U., Anti-Corrosion Methods and Materials, 50 (2003) 201-207. N OH R 1, R = H 3, R = Ph 4, R = CH 2 Ph 5, R = (CH 2 ) 11 CH 3 6, R = (CH 2 ) 13 CH 3 7, R = (CH 2 ) 17 CH 3 9 a, R = CH 2 CH(OH)(CH 2 ) 9 CH 3 9 b, R = CH 2 CH(OH)(CH 2 ) 13 CH 3 N OH R 10, R = H 11, R = CH 2 Ph

18. 18 Gravimetric Tests (Inhibition Efficiencies) Comp. 50 ppm100ppm200ppm400ppm 124.639.259.377.4 3 7.333.449.580.8 4 6.828.057.485.3 566.482.6 96.196.8 690.291.994.4 98.0 786.186.890.594.1 9a81.8 95.796.7 98.0 d 9b a 95.196.197.297.4 1012.027.345.866.1 1117.935.058.790.0 a soluble in 10% acetone in 1 N HCl; d %IE for inhibitor concentration of 10 and 25 ppm was determined to be 26.7 and 62.5, respectively. Substrate metal : Mild steel, Temperature : 60 C, Exposure : 6 hrs, Base solution : 1 N HCl

19. 19 Isotherms of compounds 9a, 1 and 10

20. 20 Tafel Tests Solution  corr, V SCE  a,, V/decade  C V/decade I corr (mA/cm 2 ) CR (mpy) Inhibition Efficiency Blank- 0.4800.17770.18132.25631031.80 4-0.50150.10040.13750.5010 229.177.8 5-0.4976 0.090340.13830.2254 103.1 90.0 10-0.46590.15910.20060.9015 412.360.0 Substrate metal : Mild steel, Temperature : 60 C, Exposure : 20 minutes, Base solution : 1 N HCl, Inhibitor Concentration : 400 ppm 1 Saeed, M. T., Ali, A. A., Rahman, S. U., Anti-Corrosion Methods and Materials, 50 (2003) 201-207.

21. 21 Cyclic Nitrones Rahman, S. U., Saeed, M. T., Ali, S. A, Anti-Corrosion Methods and Materials (Accepted).

22. 22 Cyclic Nitrones 3 1 Rahman, S. U., Saeed, M. T., Ali, S. A, Anti-Corrosion Methods and Materials (Accepted).

23. 23 Gravimetric Tests (Inhibition Efficiencies) Comp. 50 ppm100 ppm200ppm400ppm 666.178.991.191.0 730.750.068.694.4 837.658.976.394.1 10 a 92.397.097.798.3 13 a 72.682.789.490.0 15 a 97.197.497.598.2 a soluble in 10% acetone in 1N HCl Substrate metal : Mild steel, Temperature : 60 C, Exposure : 6 hrs, Base solution : 1 N HCl

24. 24 Isotherms of compounds 13, 6, 8 and 7

25. 25 Tafel Tests 1 Solution  corr, V SCE  a,, V/decade  C V/decade I corr (mA/cm 2 ) CR (mpy) Inhibition Efficiency Blank- 0.4800.17770.18132.25631031.80 (7) -0.48050.07170.107670.191487.5 91.52 (13) -0.47170.14730.16610.2594118.688.51 (15) -0.48780.099960.17310.130359.6 94.22 1 Rahman, S. U., Saeed, M. T., Ali, S. A, Anti-Corrosion Methods and Materials (Accepted).

26. 26 Conclusions  Following new compound exhibited excellent corrosion inhibition of mild steel in hot acidic medium : Isoxazolidines Cyclic Hydroxylamines Cyclic Nitrones Polar compounds with substantially bulky non-polar chains were better inhibitors.

27. 27 Future work  Gather more data in different corrosive environments.  Use mixtures of these compounds. Statistical experimental design will be beneficial  Perform toxicity studies  Study their antiscalent properties.  Study their synergy with commercial antiscalents.

28. 28 Acknowledgement  Prof. S. A. Ali,  Dr. M. T. Saeed,

29. 29 Thank you…