Novel classes of organic corrosion inhibitors

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. Applications of Corrosion Inhibitors • Water • Potable Water • Silicates, Popyphosphates, CaCO3 • 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. Factors Affecting Inhibition of Cooling Systems • Oxygen saturation • Water soluble gases • pH • TDS • Silt and solids • Sulfate bearing bacteria

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. 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. New Classes of Inhibitors • Following N containing compounds were studied • Isoxazolidines1 • Cyclic Hydroxylamines2 • Cyclic Nitrones3 • 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. Isoxazolidines Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266.

8. Isoxazolidines1 Nitrone isoxazoidines Diadducts Cycloadducts 1 Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266.

9. Quaternary Ammonium Salts1 Quaternary Amm. Salt Isoxazolidine Quaternary Amm. Salt 1 Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266.

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

11. Gravimetric Tests (Inhibition Efficiencies) Substrate metal : Mild steel, Temperature : 60 C, Exposure : 6 hrs, Base solution : 1 N HCl asoluble in 10% acetone in 1N HCl b%IE for 10 and 25 ppm were 87.2 and 91.8, respectively.

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. Isotherms of compounds 3a and 3b

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

16. Cyclic Hydroxylamines2 Hydroxylamines Nitrone Hydroxypyrrolidine Cyclic Nitrones Hydroxylamines Hydroxylamines 1 Saeed, M. T., Ali, A. A., Rahman, S. U., Anti-Corrosion Methods and Materials, 50 (2003) 201-207.

17. 1 , R = H 3 , R = P h 4 , R = C H P h 2 N R N R 5 , R = ( C H ) C H 2 1 1 3 O H O H 6 , R = ( C H ) C H 2 1 3 3 1 0 , R = H 7 , R = ( C H ) C H 2 1 7 3 1 1 , R = C H P h 2 9 a , R = C H C H ( O H ) ( C H ) C H 2 2 9 3 9 b , R = C H C H ( O H ) ( C H ) C H 2 2 1 3 3 Hydroxylamines 1 Saeed, M. T., Ali, A. A., Rahman, S. U., Anti-Corrosion Methods and Materials, 50 (2003) 201-207.

18. Gravimetric Tests (Inhibition Efficiencies) Substrate metal : Mild steel, Temperature : 60 C, Exposure : 6 hrs, Base solution : 1 N HCl asoluble 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.

19. Isotherms of compounds 9a, 1 and 10

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

22. Cyclic Nitrones3 1 Rahman, S. U., Saeed, M. T., Ali, S. A, Anti-Corrosion Methods and Materials (Accepted).

23. Gravimetric Tests (Inhibition Efficiencies) Substrate metal : Mild steel, Temperature : 60 C, Exposure : 6 hrs, Base solution : 1 N HCl asoluble in 10% acetone in 1N HCl

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

25. Tafel Tests1 1 Rahman, S. U., Saeed, M. T., Ali, S. A, Anti-Corrosion Methods and Materials (Accepted).

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

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. Acknowledgement • Prof. S. A. Ali, • Dr. M. T. Saeed,

29. Thank you…