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Novel classes of organic corrosion inhibitors
Dr. S. U. RahmanAssociate Professor, Chemical Engineering Department
King Fahd University of Petroleum & Minerals,Dhahran-31261, Saudi Arabia
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
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
Isoxazolidines1
Cyclic Hydroxylamines2
Cyclic Nitrones3
1 Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266.
2 Saeed, M. T., Ali, A. A., Rahman, S. U., Anti-Corrosion Methods and Materials, 50 (2003) 201-207.
3 Rahman, S. U., Saeed, M. T., Ali, S. A, Anti-Corrosion Methods and Materials (Accepted).
Isoxazolidines1
Nitroneisoxazoidines
Cycloadducts
Diadducts
1 Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266.
Quaternary Ammonium Salts1
1 Ali, A. A., Saeed, M. T., Rahman, S. U., Corrosion Science, 45 (2003) 253-266.
IsoxazolidineQuaternary Amm. Salt
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) 253-266.
Gravimetric Tests (Inhibition Efficiencies)
Compound 50 ppm 100 ppm 200ppm 400ppm
3a 40.7 53.6 73.8 86.7
3b 34.7 50.0 70.8 87.3
3c 98.0 98.2 98.5 98.5
3d 97.5 98.0 98.6 98.8
5a 97.0 97.2 98.5 98.8b
5b 95.2 95.7 96.0 98.3
7aa 81.9 82.3 83.4 88.1
7b 8.60 46.4 88.7 93.5
8 93.9 97.3 98.3 99.1
9 96.0 98.0 99.0 99.5
a soluble in 10% acetone in 1N HClb%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
Icorr
(mA/cm2)
CR (mpy)
Inhibition Efficiency
Blank - 0.480 0.1777 0.1813 2.2563 1031.8 0
3c - 0.491 0.0976 0.1325 0.1057 48.3 95.32
3d - 0.479 0.1330 0.1269 0.2255 103.1 90.01
5a - 0.475 0.0970 0.1170 0.1794 82.0 92.05
8 - 0.463 0.0867 0.1210 0.1107 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.
Cyclic Hydroxylamines2
(2)
N
O
RMgBr
NOH
R
3, R = Ph 4, R = CH2Ph 5, R = (CH2)11CH3
6, R = (CH2)13CH3
7, R = (CH2)17CH3
NOH
HgO
(1)
10, R = H11, R = CH2Ph
Scheme 1.
NOH
R
(8)
N
OR
OH
N
OHR
OH
(9)
NaBH4
a, R = (CH2)9CH3
b, R = (CH2)13CH3
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
Hydroxylamines
Hydroxylamines
N
OHR
1, R = H 3, R = Ph 4, R = CH2Ph 5, R = (CH2)11CH3
6, R = (CH2)13CH3
7, R = (CH2)17CH3
9 a, R = CH2CH(OH)(CH2)9CH3
9 b, R = CH2CH(OH)(CH2)13CH3
N
OH
R
10, R = H 11, R = CH2Ph
1 Saeed, M. T., Ali, A. A., Rahman, S. U., Anti-Corrosion Methods and Materials, 50 (2003) 201-207.
Gravimetric Tests (Inhibition Efficiencies)
Compounds 50 ppm 100ppm 200ppm 400ppm
1 24.6 39.2 59.3 77.4
3 7.3 33.4 49.5 80.8
4 6.8 28.0 57.4 85.3
5 66.4 82.6 96.1 96.8
6 90.2 91.9 94.4 98.0
7 86.1 86.8 90.5 94.1
9a 81.8 95.7 96.7 98.0d
9ba 95.1 96.1 97.2 97.4
10 12.0 27.3 45.8 66.1
11 17.9 35.0 58.7 90.0
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.
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
Icorr
(mA/cm2)
CR (mpy)
Inhibition Efficiency
Blank - 0.480 0.1777 0.1813 2.2563 1031.8 0
4 -0.5015 0.1004 0.1375 0.5010 229.1 77.8
5 -0.4976 0.09034 0.1383 0.2254 103.1 90.010 -0.4659 0.1591 0.2006 0.9015 412.3 60.0
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.
Cyclic Nitrones3
1 Rahman, S. U., Saeed, M. T., Ali, S. A, Anti-Corrosion Methods and Materials (Accepted).
N
O
(CH2)13CH3
OH
(15)
N
O
(CH2)9CH3
OH
(13)
O
N
(7)
N CH2
O
(6)
N (CH2)11CH3
O
(10)
O
N
(8)
Gravimetric Tests (Inhibition Efficiencies)
Compound 50 ppm 100 ppm 200ppm 400ppm
6 66.1 78.9 91.1 91.0
7 30.7 50.0 68.6 94.4
8 37.6 58.9 76.3 94.1
10a 92.3 97.0 97.7 98.3
13a 72.6 82.7 89.4 90.0
15a 97.1 97.4 97.5 98.2
asoluble in 10% acetone in 1N HCl
Substrate metal : Mild steel, Temperature : 60 C, Exposure : 6 hrs, Base solution : 1 N HCl
Tafel Tests1
Solution corr, V
SCE
a,,
V/decade
C
V/decade
Icorr
(mA/cm2)
CR (mpy)
Inhibition Efficiency
Blank - 0.480 0.1777 0.1813 2.2563 1031.8 0
(7) -0.4805 0.0717 0.10767 0.1914 87.5 91.52
(13) -0.4717 0.1473 0.1661 0.2594 118.6 88.51
(15) -0.4878 0.09996 0.1731 0.1303 59.6 94.22
1 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…