FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patents [Amendment] Rules, 2006
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
Naturally Derived Corrosion Inhibitors, Process for Preparing the Same and
Use Thereof
2. APPLICANT
NAME : Indian Oil Corporation Limited
NATIONALITY : IN
ADDRESS : G-9, Ali Yavar Jung Marg, Bandra (East), Mumbai-400 051 (IN)
3. PREAMBLE TO THE DESCRIPTION
PROVISIONAL
The following specification describes the invention :

FIELD OF THE INVENTION
The present invention relates to a naturally derived corrosion inhibitor. More particularly, the present invention provides plant derived antimicrobial agents as corrosion inhibitor, process for preparing the same and use thereof.
BACKGROUND OF THE INVENTION
Corrosion is one of the leading cause of failure for petroleum industry equipment components such as pipeline, heat exchanger, storage tanks etc. Microbiologically influenced corrosion (MIC) or bio-corrosion, refers to the process of corrosion due to the presence and activities of microorganisms and/or their metabolites. Microbiologically influenced corrosion is responsible for 40% of the internal corrosion problems in oil transportation pipelines, storage tanks, water-cooling system and fire protection systems. These systems are more sensitive for microbial attack due to the prevailing conducive growth conditions for microbial growth i.e., presence of water, metal surface, and suitable growth in normal operations.
Chemical treatments applied to control bio-corrosion involve the use of biocides and other products such as penetrating or depressive agents capable to disturb biofilms. Unfortunately, most of the chemicals used for this are inherently toxic and persistent in the environment and may lead to contamination of areas distant from the site of treatment. Environmental concern has led to legislations, which encourages the replacement of toxic chemicals, widely used in the past, with more benign chemicals that are compatible with system operation and less toxic to the environment. One innovative attempt is the use of naturally produced compounds, such as plant extracts.
A number of plant oils and aqueous plant extracts have been reported to have inhibitory activity against yeast, filamentous fungi and bacteria. Indian species such as clove, cinnamon, horse raddish, cumin, tamarind, garlic, onion, are used as preservatives, disinfectants and antiseptics. Besides that various plant extracts like Datura stramonium, Calotropis gingantea, Capparis deciduas, Prosopis juliflora have been evaluated and found to have activity against corrosion


under laboratory conditions. The corrosion inhibitory propensity of Calendula officinalis flower and tobacco extracts in steel and aluminum is also well explored in the prior arts.
The present study has been aimed to investigate the corrosion inhibition efficiency of several plant extracts on mild carbon steel coupon in presence and absence of the MIC causing microbes. Extracts of plants like neem, tobacco, lantana, capsicum, chilli etc., were prepared with several solvents and anti-microbial activities of the extracts were evaluated. Subsequently, the potential plant extracts were evaluated under static and dynamic experimental conditions, for their ability to protect against corrosion in presence and absence of MIC causing bacteria.
DESCRIPTION OF THE INVENTION
The present invention discloses about naturally derived corrosion inhibitor for Microbiologically Influenced Corrosion (MIC).
In accordance with preferred embodiment of the present invention, it is provided with isolation of MIC causing microorganism, particularly microbes of various physiological group including but are not limited to Sulphate Reducing Bacteria (SRB), Iron Related Bacteria (IRB), Acid Producing Bacteria (APB), Slime forming bacteria (Slime) and Heterotrophic Aerobic Bacteria (HAB).
The present invention discloses that the SRB is isolated by employing the Postgate-E media consisting of (g/1) KH2P04 - 0.5; NH4C1 - 1; Na2S04 - 0.1; CaC12 .6H20 - l; MgCl2.7H20 - 2, sodium lactate - 3.5; yeast extract - 1; ascorbic acid - 0.2; thioglycolic acid - 0.2 and ferrous sulphate - 0.5. The APB were isolated using media containing (g/1) KH2P04 - 0.2; (NH4)2 S04 -2.0; MgS04- 0.24; KCl - 0.10; yeast extract - 0.10; glucose -2.0 and phenol red as indicator. Further, IRB is isolated employing the media containing (g/1) FeSO4.7H2O-1.0; ammonium sulfate - 0.15; potassium chloride - 0.05; MgS04 • 7H20 - 0.5; KH2P04- 0.05 and calcium nitrate -0.01.
The aerobic heterotrophic bacteria are isolated employing (g/1) yeast extract - 10; peptone - 10; sodium chloride - 05; dibasic potassium phosphate - 2.5 and glucose - 2.5. Slime forming bacteria were isolated using media containing (g/1) yeast extract - 0.1; peptone - 0.5; MgCl2 - 0.2 and NaCl - 1.6. The SRB is isolated and cultivated anaerobically while other groups of bacteria


are cultivated in shaking conditions at 200 rpm. All bacteria were incubated at 30°C. Inoculum (consortium) was prepared by mixing of fully-grown culture of each type of the microbes in equal ratio.
Further, the invention provides a process for preparation of plant extracts for the screening of antimicrobial activity wherein, the process comprises of extracting all or any specific part of the plant/s employing any suitable extraction technique, preferably a hot-soxhalation and wherein a selective solvent or solvent system are used to yield high extractive value. Said solvent is selected from any organic solvents, preferably selected from n-hexane and/or methanol, alone or in combination thereof.
According to the present invention, the preparation of plant extracts is disclosed herein for the anti-bacterial screening, and wherein it provides the details of the plant and their part used for the said study. In order to extract the active ingredients, any preferred parts of the plants were minced and grinded in spice grinder and dried at 70°C overnight and powdered (Table 1). The powder is subjected to suitable extraction techniques preferably through hot soxhalation method.
Table-1: Details of plant, their parts used and dry weight of extracts obtained with hexane and methanol

S.No. Plant & Part Used Solvent Initial Dry
Weight
(g) Dry Weight of crude extract (g)
1. Piper nigrum/B\ack Pepper (Seed) Hexane 20 1.01
2. Piper nigrum/B\ack Pepper (Seed) Methanol 20 2.12
3. Capsicum sp. Chilli fruit Hexane 25 1.70
4. Capsicum sps. Chilli fruit Methanol 30 2.10
5. Capsicum annum/Capsicum Hexane 25 0.21
6. Capsicum annum/Capsicum Methanol 20 0.89
7. Azadirachta indica, Neem (Seed) Hexane 20 2-lg
8. Azadirachta indica, Neem (Seed) Methanol 20 2-3 g
9. Lantana camara (Seed) Hexane 20 1.02


10. Lantana camara (Seed) Methanol 20 1.15
11. Ocimum sanctum/Tulasi (leaves) Hexane 20 0.52
12. Ocimum sanctum/Tulasi (leaves) Methanol 20 0.92
13. Nicotiana tabacum Tobacco (leaves, stem, dust) Hexane 25 1.05
14. Nicotiana tabacum Tobacco (leaves, stem, dust) Methanol 25 1.62
15. Lawsonia inermis Mahendi (leaves) Hexane 20 1.01
16. Lawsonia inermis Mahendi (leaves) Methanol 20 1.24
According to the present invention, anti microbial screening for the plant extracts are carried out against SRB, APB, HAB, IRB, slime forming bacteria and consortium of bacteria by dilution method, Minimum Inhibitory Concentration is determined and wherein the log phase culture is used as inoculums (1% v/v, 4.2 x 108 CFU/ml). Further, the growth of the microbes is monitored by visual observation as well as counting the CFU/ml on respective media. The growth is compared with control i.e., with out the plant extract.
The data on minimum inhibitory concentration of 16 plant extract against various group of microbes commonly associated with MIC is shown in Table 2. Further, the antimicrobial activity of various natural plant extract differs according to the various microbial groups; however, the plant extracts are effective against both aerobic as well as anaerobic microbes. Based on the minimum inhibitory concentration data against consortium of the MIC causing microbes, the plant extracts namely, lantana, tobacco, neem and chilli having minimum inhibitory concentration below 3200 ppm is selected. These extracts are effective against the growth of the total, planktonic (floating) and sessile bacterial count (data not shown).
Table- 2: Inhibitory concentration of chemical biocides and plant extract against various bacterial groups and their mixture

Minimum inhibitory concentration (ppm)


S.No Chemical/ Plant extract Solvent for extraction IRB APB HAB Slime SRB Consortium of bacteria (IRB, APB, HAB, Slime and SRB)
1. Triazine based biocide 200 200 200 200 400 430
2. Black Pepper (Seed) Hexane 5000 5000 5000 5000 2000 5500
3. Black Pepper (Seed) Methanol 1000 3000 3000 4000 2000 4500
4. Chilli fruit Hexane 2500 1800 1500 2000 2200 3200
5. Chilli fruit Methanol 1000 4000 5000 4500 2000 4800
6. Capsicum Hexane 2000 4100 4800 4400 4000 4500
7. Capsicum Methanol 1000 1000 3200 1000 2000 3400
8. Neem (Seed) Hexane 1000 1000 2700 1000 1200 2900
9. Neem (Seed) Methanol 1200 1500 1000 1150 1750 2100
10. Lantana (Seed) Hexane 1600 1500 1750 1970 1700 2200
11. Lantana (Seed) Methanol 1000 1700 1450 1500 2050 2050
12. Tulasi (leaves) Hexane 2000 2010 1560 1700 2450 2500
13. Tulasi (leaves) Methanol 3000 2000 1400 1200 1470 3250
14. Tobacco(leaves, stem, dust) Hexane 2100 2300 4500 3700 1890 4670
15. Tobacco(leaves, stem, dust) Methanol 1200 1700 1550 1625 1754 2350
16. Mahendi (leaves) Hexane 1120 1560 2750 1490 2000 3590
17. Mahendi (leaves) Methanol 1400 1450 2100 1400 1200 2430
The present invention discloses about the corrosion protection ability of the natural derived plant extracts along with commercial corrosion inhibitors (CI) and chemical biocides in presence and absence of MIC causing bacteria is evaluated in aggravated static and dynamic laboratory conditions. The mild carbon steel coupons are polished, washed with water and acetone. The


diameter and thickness of each coupon is determined. The static test is conducted in beakers while dynamic test is conducted by dynamic 'Wheel test'. The plant extracts are initially evaluated for their ability to protect from the corrosion in static test and potential extracts are further evaluated in dynamic test. The static test is conducted for around 60 days while dynamic test is conducted for 30 days. The experiments are terminated after removing the coupons and washed by neutralized acid to remove the corrosion products, and subsequently rinsed with sterile distilled water and dried. Final weight of the coupons in each system is recorded and corrosion rate of the metal coupons are calculated according to following formula:
Corrosion rate = (K x W)/ (A x T x D)
Where, K= 3450000 (constant used to determine corrosion rate in miles per year (mpy)); T = Time of exposure (h); W= Weight loss (g); D= Density (g/cm3); A= Surface area (cm3)
Further, the corrosion rate data under various experimental conditions in "Wheel test" are presented in Table- 3.The corrosion rate data indicates that the selected plant extracts is able to inhibit the general corrosion as well as the MIC. These results suggest that the chemical biocides as well as plant extracts are able to inhibit the growth of MIC causing microbes and resulted in decreased corrosion rate in presence of corrosion inhibitor (CI). These results further indicate that the natural plant extracts alone is effective in corrosion protection in presence of MIC causing microbes suggesting their corrosion inhibitive and antimicrobial activity. However, the chemical biocide is effective only in presence of CI for the protection against MIC.
Table- 3: Corrosion rate (mpy) in Wheel test after 30 days.
Plant extracts and chemical biocide are taken at their minimum inhibitory
concentrations;
Inoculum: consortia, 8.0 X 108 cfu/ml; speed: 12-16 rpm; Temperature: 38-40° C;
biocide: triazine based;
CI (commercial corrosion inhibitor) concentration: 9 ppm.

S.No. Test condition Corrosion rate (mpy)
1 A' 6.4
2 A* + Inoculum 8.2
3 A* + CI 2.6


4 A* + CI + Inoculum 8.7
5 A* + CI + Inoculum + Biocide 3.2
6 A* + Inoculum + Biocide 7.1
7 A* + CI + Inoculum + Chilli extract 3.4
8 A* + Inoculum + Chilli extract 3.6
9 A* + Chilli extract 3.2
10 A* + CI + Inoculum + Tobacco extract 3.6
11 A* + Inoculum + Tobacco extract 3.5
12 A* + Tobacco extract 3.5
13 A* + CI + Inoculum + Neem extract 3.2
14 A* + Inoculum + Neem extract 3.4
15 A* + Neem extract 3.7
16 A* + CI + Inoculum + Lantana extract 3.1
17 A* + Inoculum + Lantana extract 3.2
18 A* + Lantana extract 3.2
A : 125 ml of diesel with 2% water containing 70-ppm chloride
Based on research, we ensure that there is no prior art which recites about the plant extracts with the ability to protect from general corrosion as well as bio-corrosion. In the present study, it is observed that the plant extract, besides having antimicrobial activity, are adsorbed on the metal surface and decrease the surface area available for cathodic and anodic reaction to take place. These results provided an insight for the development of natural, and therefore more environmentally benign, biocide/corrosion inhibitors than those are currently in use for the control of corrosion and MIC.
In the present invention, various plant extracts like Neem, Tobacco, Chilli, Lantana and Mahendi is evaluated for their potential to act as corrosion inhibitor for the carbon steel materials under microbiologically influenced corrosion prevailing conditions. The experimental results under static and dynamic conditions on metallic coupons indicate that the crude extract of various


plants like Neem, Tobacco, Chilli, Lantana and Mahendi having inhibitory activity against MIC causing microbes. Further it is revealed that the plant extracts are effective to inhibit the general corrosion as well.
While this provisional patent application contains the description of the principal inventive concepts, the complete patent application pursuant here to, will fully and particularly describe the preferred embodiments of the present invention.