Compositions – Preservative agents – Anti-corrosion
Reexamination Certificate
1999-09-22
2001-01-09
Warden, Jill (Department: 1743)
Compositions
Preservative agents
Anti-corrosion
C252S390000, C148S243000, C148S274000, C208S047000, C208S04800Q, C106S014120, C106S014130, C106S014150, C106S014180, C106S014310, C106S014270, C422S007000, C422S012000, C546S001000, C546S268100, C546S290000
Reexamination Certificate
active
06171521
ABSTRACT:
TECHNICAL FIELD
This invention concerns zwitterionic water-soluble imine corrosion inhibitors, compositions comprising the corrosion inhibitors and a method of inhibiting corrosion of ferrous metal surfaces in contact with corrosive fluids.
BACKGROUND OF THE INVENTION
This invention relates to a method for inhibiting the corrosion of ferrous metals. More particularly, this invention concerns a method for inhibiting corrosion of a ferrous metal subjected to aqueous acid environments. In narrower aspects, the present invention relates to an acidizing process for the removal of calcareous scale formations from a ferrous metal surface whereby corrosive attack of the metal substrate is inhibited.
In many industrial practices, the need to contact ferrous metal surfaces with strong acidic agents constantly arises. Particularly under numerous industrial circumstances equipment fabricated of ferrous metals such as boilers often accumulate scale formations which must be periodically removed in order to maintain the efficiency of the equipment involved. For example, it is common within the petroleum industry to utilize heater tubes in contact with crude oil containing emulsified aqueous solutions of inorganic salts, particularly those of calcium, in order to effect separation of oil and water. The briny solution, upon contacting the heated metallic surfaces, deposits a substantial portion of mineral content upon said surfaces in a form of insoluble calcareous formations. Consequently, in order to maintain reasonable efficiency of the heaters and to obviate burning out of the heater tubes it is necessary to remove the scale formations periodically that have formed. The latter is but one example of many of such operations in the petroleum field which requires frequent acidizing treatment of various pieces of equipment made of iron or a ferrous alloy. Also in many chemical processes it is necessary to store or transport acids, such as the common mineral acids, while in contact with ferrous metals. Accordingly, it can be seen that the practical situations necessitating the minimizing or obviating of the corrosive effect acidic materials, especially those of mineral origin, upon ferrous metal surfaces are legion.
Flow-induced localized corrosion (FILC) is a result of high shear conditions present in flow lines. The amount of corrosion that occurs is dependent on a variety of factors including the corrosiveness of the fluid flowing through the lines, the metallurgy of the line and the ability of added corrosion inhibitors to maintain adhesion to the interior of the line.
The ability of added corrosion inhibitors to maintain adhesion to the interior of the line depends on both the chemical adhesive properties of the inhibitor and the shear stress conditions which exist inside the line. A number of products have shown promise as shear-resistant corrosion inhibitors. Included among the corrosion inhibitors are amides and quaternized amines and amide amine salts.
Many nitrogen-containing corrosion inhibitors are known. Among them are: morpholine, disclosed in U.S. Pat. No. 3,649,167; imidazolines in U.S. Pat. No. 3,197,403; amidic acids in U.S. Pat. No. 2,742,498; bis-amides in U.S. Pat. No. 4,344,861; amines in U.S. Pat. Nos. 5,211,840 and 5,714,664; amides in U.S. Pat. No. 5,556,575; and carbohydrazides in U.S. Pat. No. 5,078,966. The reaction of acrylic acid with substituted imidazolines to form various amine derivative corrosion inhibitors has been disclosed in U.S. Pat. Nos. 5,300,235; 5,322,630; 5,322,640 and 5,427,999.
Schiff bases have been disclosed as corrosion inhibitors in U.S. Pat. No. 5,147,567, in
Materials Chemistry and Physics,
39 (1995) 209-213 and in
Corrosion Science,
26 (1986) 827-837. Moreover, imines have also been disclosed as corrosion inhibitors, and as additives to corrosion inhibitor formulations. For example, imines have been disclosed as useful in conjunction with aromatic triazoles to enhance corrosion inhibition in U.S. Pat. No. 4,642,221; and imine dispersants have been utilized to enhance the activity of trithiones as CO
2
corrosion inhibitors in EP 0 275 651. Imines have been disclosed as corrosion inhibitors in U.S. Pat. No. 4,490,293; JP 74021024B and SU 318315A.
SUMMARY OF THE INVENTION
I have discovered certain novel zwitterionc imine compositions which inhibit corrosion of ferrous metal surfaces in contact with acidic fluids which contain water. Accordingly, in its principal aspect, this invention is directed to a zwitterionic water-soluble imine of formula:
wherein
R
1
is selected from heterocyclyl, heteroaryl, aryl, arylalkyl, cycloalkyl and alkyl;
R
2
is selected from alkyl, alkenyl, aminoalkyl, diaminoalkyl, hydroxyalkyl, alkoxyalkyl, thioalkyl, alkylthioalkyl and arylalkyl;
R
3
is selected from hydrogen and lower alkyl, or R
1
and R
3
taken together form a cycloalkyl,
p is 2, 3, 4 or 5; and
Z is CO
2
−
, OCO
2
−
, SO
3
−
, OSO
3
−
, PO
3
−
or OPO
3
−
.
DETAILED DESCRIPTION OF THE INVENTION
“Alkyl” means a monovalent group derived from a straight or branched chain saturated hydrocarbon by the removal of a single hydrogen atom. Preferred alkyls are straight chain C
6
-C
24
alkyl groups. More preferred alkyls are straight chain C
12
-C
24
alkyl groups. Representative alkyls are the hydrocarbon residues of caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid and stearic acid.
“Lower alkyl” means a C
1
-C
5
straight or branched chain alkyl group. Representative lower alkyl include methyl, ethyl, propyl, isopropyl, butyl, and the like.
“Alkylene” means a divalent group derived from an alkyl as defined herein by the removal of two hydrogen atoms. Representative alkylene include methylene, ethylene, propylene, and the like.
“Alkenyl” means a monovalent group derived from a hydrocarbon containing at least one carbon-carbon double bond by the removal of a single hydrogen atom. Preferred alkenyls are straight chain C
6
-C
20
alkenyl groups containing 1, 2 or 3 double bonds. More preferred alkenyls are straight chain C
16
-C
20
alkenyl groups containing 1, 2 or 3 double bonds. Still more preferred alkenyls are the hydrocarbon residues of palmitoleic acid, oleic acid, linoleic acid and linolenic acid.
“Alkoxy” and “alkoxyl” mean a lower alkyl-O— group. Representative alkoxy groups include methoxy, ethoxy, propoxy, butoxy, and the like.
“Alkoxyalkyl” means a lower alkyl-O-alkylene group where the lower alkyl is defined herein and the alkylene is a straight chain alkylenyl radical of two to about five carbon atoms. Representative alkoxyalkyl groups include ethoxyethyl, propoxyethyl, butoxyethyl, and the like.
“Hydroxyalkyl” means a straight chain lower alkyl of two to about 5 carbon atoms substituted with hydroxy. Representative hydroxyalkyl groups include 2-hydroxyethyl, 3-hydroxypropyl, and the like.
“Thioalkyl” means a straight chain lower alkyl of two to about 5 carbon atoms substituted with —SH. Representative thioalkyl groups include 2-thioethyl, 3-thiopropyl, and the like.
“Alkylthioalkyl” means a lower alkyl-S-alkylene- group where the lower alkyl is defined herein and the alkylene is a straight chain alkylenyl radical of two to about five carbon atoms. Representative alkylthioalkyl groups include methylthioethyl, ethylthioethyl, methylthiopropyl, and the like.
“Aminoalkyl” means a Y
1
NH—(CH
2
)
n
— group where n is 2 or 3 and Y
1
is C
1
-C
30
alkyl or C
2
-C
30
alkenyl. Preferred alkyl groups are C
1
-C
11
alkyl. More preferred alkyl groups are C
1
-C
5
alkyl. Preferred alkenyl groups are the hydrocarbon residues of palmitoleic acid, oleic acid, linoleic acid and linolenic acid.
“Diaminoalkyl” means a Y
1
NH—(CH
2
)
n
—NH—(CH
2
)
m
— group wherein Y
1
and n are defined herein and m is 2 or 3. Preferred alkyl groups are C
1
-C
11
alkyl. More preferred alkyl groups are C
1
-C
5
alkyl. Preferred alkenyl groups are the hydrocarbon residues of palmitoleic acid, oleic acid, linoleic acid and linolenic acid.
“Cycloalkyl” means a non-aromatic monocyclic ring system of about 5 to about 6
Breininger Thomas M.
Cole Monique T.
Martin Michael B.
Nalco/Exxon Energy Chemicals L.P.
Warden Jill
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