Novel classes of organic corrosion inhibitors

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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

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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

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Factors Affecting Inhibition of Cooling Systems

Oxygen saturation Water soluble gases pH TDS Silt and solids Sulfate bearing bacteria

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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

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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

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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).

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Isoxazolidines

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

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Isoxazolidines1

Nitroneisoxazoidines

Cycloadducts

Diadducts

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

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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

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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.

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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

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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)

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Isotherms of compounds 3a and 3b

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.5 1.7 1.9 2.1 2.3 2.5 2.7

log C (ppm)

, su

rfa

ce c

ove

rag

e

Fig. 2.

(a)

(b)

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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.

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Cyclic Hydroxylamines

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

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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

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Hydroxylamines

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

NOH

R

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

NOH

R

10, R = H 11, R = CH2Ph

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Gravimetric Tests (Inhibition Efficiencies)

Comp. 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

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Isotherms of compounds 9a, 1 and 10

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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.

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Cyclic Nitrones

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

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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)

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Gravimetric Tests (Inhibition Efficiencies)

Comp. 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

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Isotherms of compounds 13, 6, 8 and 7

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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).

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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.

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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.

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Acknowledgement

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

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Thank you…