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

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

Factors Affecting Inhibition of Cooling Systems  Oxygen saturation  Water soluble gases  pH  TDS  Silt and Solids  Sulfate bearing Bacteria

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

New Classes of Inhibitors  Isoxazolidines 1  Cyclic Hydroxylamines 2  Cyclic Nitrones 3 1 Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) Saeed, M. T., Ali, A. A., Rahman, S. U., Anti-Corrosion Methods and Materials, 50 (2003) Rahman, S. U., Saeed, M. T., Ali, S. A, Anti-Corrosion Methods and Materials (Accepted).

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

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

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

Gravimetric Tests (Inhibition Efficiencies) Compound 50 ppm100 ppm200ppm400ppm 3a b c d a b 5b a a b 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

Tafel Tests Solution  corr, V SCE  a,, V/decade  C V/decade I corr (mA/cm 2 ) CR (mpy) Inhibition Efficiency Blank c d a 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)

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

1 Saeed, M. T., Ali, A. A., Rahman, S. U., Anti-Corrosion Methods and Materials, 50 (2003)

Gravimetric Tests (Inhibition Efficiencies) Compounds 50 ppm100ppm200ppm400ppm a d 9b a 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

Tafel Tests Solution  corr, V SCE  a,, V/decade  C V/decade I corr (mA/cm 2 ) CR (mpy) Inhibition Efficiency Blank 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)

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

Gravimetric Tests (Inhibition Efficiencies) Compound 50 ppm100 ppm200ppm400ppm a a a a soluble in 10% acetone in 1N HCl Substrate metal : Mild steel, Temperature : 60 C, Exposure : 6 hrs, Base solution : 1 N HCl

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

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.

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 anti-scalent properties.  Study their synergy with commercial anti-scalents.

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

Thank you…