Patent Description:
Metal corrosion is a ubiquitous phenomenon costing the global economy trillions of dollars annually. Besides, corrosion can also lead to catastrophic explosions and consequent loss of material and life. In general terms, corrosion is the deterioration of a metal or an alloy when exposed to the environment. Corrosion cannot be stopped but it can be reduced to certain extent. There are several ways by which corrosion reduction can be made possible, viz. , by using paints, coatings, corrosion resistant alloys, etc. However, the use of corrosion inhibitors is one of the most economical and effective ways to combat corrosion in the industry. Corrosion inhibitors are generally organic or inorganic compounds which when used in small (usually in parts per million) quantities reduce the corrosion significantly through formation of a protective film or through similar such mechanisms. Corrosion inhibitors are extensively used for a wide variety of applications in the industry. In particular, the oil and gas industry uses corrosion inhibitors for acid well stimulation for enhancing oil recovery from rock formations. Conventional process of screening and designing of a corrosion inhibitor is largely empirical and, therefore, extremely time consuming and expensive. Besides, there is a need for design of corrosion inhibitors which are efficient at high temperatures.

Performance of several corrosion inhibitors which are used conventionally depends on the medium treated, the type of surface that is susceptible to corrosion, the type of corrosion encountered, and the conditions to which the medium is exposed. Further, the most corrosion inhibitors do not show strong binding with iron and iron alloys surface and hence iron and iron alloys structures loses luster in presence of most of the conventionally used corrosion inhibitors. Further, an efficient and durable inhibitor that can effectively protect iron and iron alloys in aggressive environments such as high temperature for longer duration without affecting the luster is yet to be realized.

<CIT> discloses an acidic oil extraction medium corrosion inhibitor, which contains thiourea and hexamethylenetetramine, wherein the mass ratio of thiourea to hexamethylenetetramine is <NUM>:<NUM>-<NUM>:<NUM>. The acidic oil extraction medium corrosion inhibitor disclosed by the invention is high in corrosion inhibition, especially applicable to the corrosion prevention of N80 steel in an acidic oil extraction medium, namely, an ammonium persulfate solution, in an oilfield, wherein the mass concentration of ammonium persulfate is <NUM>-<NUM>% (wt. ), and the corrosion temperature is set at <NUM>-<NUM> DEG C; the acidic oil extraction medium corrosion inhibitor is low in toxicity, and especially suitable for the occasions with high environmental requirements.

<CIT> discloses a method of treating in a subterranean formation including placing a corrosion inhibitor composition into a subterranean formation, where the formation includes an acidic environment having a pH of about <NUM> or below, where the composition includes: an organic solvent comprising an alcohol with a flash point of at least about <NUM>; a nitrogen containing compound; an aqueous acid solution comprising HC1; and contacting a metal surface with the corrosion inhibitor composition. A corrosion inhibitor composition includes an organic solvent comprising an alcohol with a flash point of at least about <NUM>; a nitrogen containing compound; and an aqueous acid solution comprising HC1.

<CIT> discloses a composite corrosion inhibitor for inhibiting corrosion of steel in a CO2, H2S, HCl coexistence environment in the processes of oil-gas-water treatment and raw oil refining process. Preparation of the composite corrosion inhibitor involves adding imidazoline to thiourea solution, heating, and adding organic polyamine to the mixture. First an organic solvent solution A of <NUM>% thiocarbamide is prepared; imidazoline is added with H3BO3 as a catalyst and then reacts with the solution A to prepare a reaction product (I). Organic polyamine and a urea compound are mixed to prepare a reaction product (II) at <NUM>-<NUM>. The reaction product (I) and the reaction product (II) are mixed at the mass ratio of (<NUM>:<NUM>) to (<NUM>:<NUM>) to obtain the composite corrosion inhibitor.

SULAIMAN KAZEEM O ET AL discloses the corrosion inhibition of mild steel in an an aqueous acid solution containing HCl with aromatic hydrazide derivatives such as <NUM>-(<NUM>,<NUM>,<NUM>-tri-R-benzylidene) hydrazinecarbothioamide, (R = H, CH3, OCH3 and NH2). PRITHVI ET AL discloses the corrosion inhibition of mild steel in an an aqueous acid solution containing HCl, H2SO4 and H3PO4 with <NUM>-[<NUM>-(dimethylamino) benzylidene] hydrazinecarbothioamide (DABHC).

The present disclosure present technological improvements as solutions to one or more of the above-mentioned technical problems recognized by the inventors in the conventional corrosion inhibitors.

Most of the conventional corrosion inhibitor compounds are either not so effective or require large amount of inhibitor for adequate protection. The inefficient corrosion inhibitor results in structural failure leading to serious economic, environmental and human losses. Further, most corrosion inhibitors do not show such strong binding with the surface of iron and iron alloys and the material loses luster i.e. corrodes in presence of most of the conventional corrosion inhibitors.

The present disclosure addresses the problem of acid corrosion of iron and iron alloys which is relevant for a wide variety of industries such as oil and gas production and acid pickling etc. The technical solution provided in the present disclosure is a new corrosion inhibitor composition comprising an effective amount of Naphthalene-<NUM>-thiocarboxamide dissolved in an organic solvent for iron and iron alloys in hydrochloric acid i.e. HCl media. This is specifically relevant for acid well stimulation in the oil and gas industries.

In an embodiment, the corrosion inhibitor composition comprising an effective amount of Naphthalene-<NUM>-thiocarboxamide dissolved in an organic solvent is providing ~<NUM>-<NUM> percentage corrosion inhibition efficiency in <NUM> HCl for mild iron and iron alloys at a very low concentration of <NUM> millimolar (mM).

<FIG> is a functional block diagram of a computing machine/system <NUM> for selecting optimal corrosion inhibitor molecule, in accordance with some embodiments of the present disclosure. The system <NUM> includes or is otherwise in communication with hardware processors <NUM>, at least one memory such as a memory <NUM>, an I/O interface <NUM>. The hardware processors <NUM>, memory <NUM>, and the Input /Output (I/O) interface <NUM> may be coupled by a system bus such as a system bus <NUM> or a similar mechanism. In an embodiment, the hardware processors <NUM> can be one or more hardware processors.

The I/O interface <NUM> may include a variety of software and hardware interfaces, for example, a web interface, a graphical user interface, and the like. The I/O interface <NUM> may include a variety of software and hardware interfaces, for example, interfaces for peripheral device(s), such as a keyboard, a mouse, an external memory, a printer and the like. Further, the I/O interface <NUM> may enable the system <NUM> to communicate with other devices, such as web servers, and external databases.

The I/O interface <NUM> can facilitate multiple communications within a wide variety of networks and protocol types, including wired networks, for example, local area network (LAN), cable, etc., and wireless networks, such as Wireless LAN (WLAN), cellular, or satellite. For the purpose, the I/O interface <NUM> may include one or more ports for connecting several computing systems with one another or to another server computer. The I/O interface <NUM> may include one or more ports for connecting several devices to one another or to another server.

The one or more hardware processors <NUM> may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, node machines, logic circuitries, and/or any devices that manipulate signals based on operational instructions. Among other capabilities, the one or more hardware processors <NUM> is configured to fetch and execute computer-readable instructions stored in the memory <NUM>.

The memory <NUM> may include any computer-readable medium known in the art including, for example, volatile memory, such as static random access memory (SRAM) and dynamic random access memory (DRAM), and/or non-volatile memory, such as read only memory (ROM), erasable programmable ROM, flash memories, hard disks, optical disks, and magnetic tapes. In an embodiment, the memory <NUM> includes a plurality of modules <NUM>. The memory <NUM> also includes a data repository (or repository) <NUM> for storing data processed, received, and generated by the plurality of modules <NUM>.

The plurality of modules <NUM> include programs or coded instructions that supplement applications or functions performed by the system <NUM> for automated authoring of purposive models from NL documents. The plurality of modules <NUM>, amongst other things, can include routines, programs, objects, components, and data structures, which performs particular tasks or implement particular abstract data types. The plurality of modules <NUM> may also be used as, signal processor(s), node machine(s), logic circuitries, and/or any other device or component that manipulates signals based on operational instructions. Further, the plurality of modules <NUM> can be used by hardware, by computer-readable instructions executed by the one or more hardware processors <NUM>, or by a combination thereof. The plurality of modules <NUM> can include various sub-modules (not shown). The plurality of modules <NUM> may include computer-readable instructions that supplement applications or functions performed by the system <NUM> for the semantic navigation using spatial graph and trajectory history.

The data repository (or repository) <NUM> may include a plurality of abstracted piece of code for refinement and data that is processed, received, or generated as a result of the execution of the plurality of modules in the module(s) <NUM>. In an embodiment, the data repository <NUM> includes a molecular database comprising a plurality of molecular details.

Although the data repository <NUM> is shown internal to the system <NUM>, it will be noted that, in alternate embodiments, the data repository <NUM> can also be implemented external to the system <NUM>, where the data repository <NUM> may be stored within a database (repository <NUM>) communicatively coupled to the system <NUM>. The data contained within such external database may be periodically updated. For example, new data may be added into the database (not shown in <FIG>) and/or existing data may be modified and/or non-useful data may be deleted from the database. In one example, the data may be stored in an external system, such as a Lightweight Directory Access Protocol (LDAP) directory and a Relational Database Management System (RDBMS). Working of the components of the system <NUM> are explained with reference to the method steps depicted in <FIG>, FIGS. 6A and FIG.

The present disclosure identified the Naphthalene-<NUM>-thiocarboxamide molecule as the corrosion inhibitor using a computational method based on the HOMO- LUMO (Highest Occupied Molecular Orbital - Lowest Unoccupied Molecular Orbital) energy gap values of the plurality of molecules. In an embodiment, the computational method for identifying an optimal corrosion inhibitor molecule is performed using the computing machine <NUM> shown in <FIG>. Initially, a plurality of molecules or molecular details are obtained from a molecular database. Further, the HOMO-LUMO energy gaps are computed for each of the plurality of molecules obtained from the molecular database using Density Functional Theory (DFT) based techniques. Further, a plurality of potential molecules with the lowest HOMO-LUMO energy gap values are identified from the plurality of molecules based on a threshold. Further, a detailed DFT-based adsorption studies are performed on the plurality of potential molecules on a representative surface such as Fe (<NUM>) for iron and iron alloys, to compute its adsorption energy values. Further, the adsorption energy values of each of the plurality of potential molecules are compared with a known inhibitor compound (as reference) like trans-cinnamaldehyde, wherein, higher the magnitude of adsorption energy better the inhibitor. Further, an optimal molecule (for example, Naphthalene-<NUM>-thiocarboxamide) is selected based on the adsorption energy values, where in a molecule having higher adsorption energy magnitude than the reference like trans-cinnamaldehyde is taken. In an embodiment, it was identified that the adsorption energy of napthalene-<NUM>-thiocarboxamide (Eads = -<NUM> kcal/mol) to be almost <NUM> percent higher than that of trans-cinnamaldehyde thus showing its excellent potential as a corrosion inhibitor. Finally, the optimal corrosion inhibitor molecule is validated experimentally using standard weight loss tests of carbon steel samples in <NUM> molar HCl containing <NUM> millimolar (mM) concentration of the molecule selected in an organic solvent or inhibitor composition.

The method to identify the optimal corrosion inhibitor molecule explained above in brief is in accordance with inventor's <CIT>. Thus, the entire optimal corrosion inhibitor molecule identification approach is not reexplained herein for brevity.

In embodiment, the corrosion inhibitor composition is included/added in the commodity and/or corrosive substances (for example, oil, gas, acid, alkaline, fertilizer and the like) stored in storage space or in transportation of the same via pipeline or umbilical, wherein the said corrosion inhibitor composition forms a layer on the metal.

In embodiment, the corrosion inhibitor composition is applied on a metal surface before introducing the commodity and/or corrosive substances in storage space or in transportation of the same via pipeline or umbilical or any kind of containers (for example, acid pickling, acid well stimulation, acid wash, scale removal and the like).

In another embodiments, the corrosion inhibitor composition is used in drilling and machining applications to protect iron and iron alloys. In said applications, the corrosion inhibitor composition is used with or without lubricants/coolants. For example, in some applications, the corrosion inhibitor composition is used in combination with lubricants/coolants. In some other applications, the corrosion inhibitor composition is used without lubricants/coolants.

The structure of the Naphthalene-<NUM>-thiocarboxamide molecule is shown in <FIG> and the quantum chemical descriptors of Naphthalene-<NUM>-thiocarboxamide is given in Table I. Now referring to Table I, the quantum chemical descriptors of Naphthalene-<NUM>-thiocarboxamide are compared to Trans Cinnamaldehyde. It is observed that Naphthalene-<NUM>-thiocarboxamide shows very low energy gap even lower than the commercially used trans-cinnamaldehyde. The identified molecule (Naphthalene-<NUM>-thiocarboxamide) strongly binds with the metal surface, metal being one of iron and iron alloys as illustrated in <FIG>, acting as barrier between corrosive element, and metal surface thus protecting iron and iron alloys from corrosion. Now referring to <FIG>, naphthalene-<NUM>-thiocarboxamide adsorbs on iron surface in flat orientation. S, N and C atoms of naphthalene-<NUM>-thiocarboxamide make chemical bonds with iron surface atoms, forming a strong, impermeable layer on the surface of iron and iron alloys. Further, this strong impermeable layer of Naphthalene-<NUM>-thiocarboxamide protects iron and iron alloys from degradation and thus, the luster of the iron and iron alloys remains intact even after exposed to/left in acid.

Further, experimental validation via standard weight loss tests of mild steel samples in <NUM> HCl containing <NUM> millimolar (mM) concentration of the inhibitor molecule is performed. The inhibition efficiency of napthalene-<NUM>-thiocarboxamide is ~<NUM>-<NUM> percent as shown in Table II. Whereas the inhibition efficiency of trans-cinnamaldehyde even at <NUM> is <NUM> percent in <NUM> HCl for the same mild steel.

In an embodiment, the present disclosure is experimented as follows: The examples of corrosion inhibition effect of the molecule i.e. Naphthalene <NUM>-thiocarboxamide on iron (Fe) and iron alloys, are given at two temperatures. In an embodiment, the composition of the iron and iron alloys used to test the inhibitor molecule is <NUM>. 044C-<NUM>. 04Si-<NUM>. 15Mn-<NUM>. 028P-<NUM>-<NUM>. 051Cr-<NUM>. 001Mo-<NUM>. 001Ni-<NUM>. 052Cu-<NUM>. 011V-Balance Fe, all the amounts of elements are in weight percentages. Here, C is Carbon, Si is Silicon, Mn is Manganese, P is Phosphorous, S is Sulphur, Cr is Chromium, Mo is Molybdenum, Ni is Nickel, Cu is Copper, and V is Vanadium.

The mild steel coupons were initially abraded with various emery papers of decreasing coarseness i.e. <NUM>, <NUM>, <NUM>, <NUM> grits to obtain a fine finish surface. The fine finished coupons are cleaned with acetone and further wrapped in a paper to avoid any further oxidation and stored in a safe and dry place until further use.

Further, the <NUM> grit finished coupons are immersed in <NUM> <NUM> HCl solution for 2hrs at room temperature and at <NUM>, to find out the corrosion rate. Similarly, the fine finished coupons are also immersed in <NUM> <NUM> HCl along with the inhibitor composition i.e. Naphthalene <NUM>-thiocarboxamide dissolved in tetrahydrofuran, with an effective concentration of inhibitor <NUM> for 2hrs at the above temperatures.

The below table provides the information on test results. The average Corrosion Rates (CR) at room temperature and <NUM> in <NUM> HCl without inhibitor for 2hrs immersion are <NUM>/y and <NUM>/y respectively. The Inhibition Efficiency (IE) is calculated using the formula given below.

Claim 1:
A corrosion inhibitor composition for inhibiting corrosion of iron and iron alloys, the corrosion inhibitor composition comprising: an effective amount of a naphthalene-<NUM>-thiocarboxamide dissolved in an organic solvent, wherein the effective amount of the corrosion inhibitor composition introduced into an environment is in the range from <NUM> to <NUM> parts per million by volume.