Antifreeze corrosion inhibitors

J. W. Darden, C. A. Triebel, W. A. Van Neste, and J. P. Maes. Monobasic-dibasic acid/salt antifreeze corrosion inhibitor. Patent EP 229440, 1987. 

Chemical Specialties Manufacturers Association 1001 Connecticut Avenue, NW Washington, D.C. 20036 Standard Reference TestingMaterials for insecticides (see Insect control technology), cleaning products, sanitizers, brake fluids, corrosion inhibitors (see Corrosion and corrosion control), antifreezes, poHshes, and floor waxes. 

Corrosion Inhibitors. Steel-reinforcing wire and rods embedded in concrete containing quinoline or quinoline chromate are less susceptible to corrosion (72) (see Corrosion and corrosion control). Treating the surface of metals with 8-hydroxyquinoline [148-24-3] makes them resistant to tarnishing and corrosion (73). Ethylene glycol-type antifreeze may contain quinoline, 2-chloro-, 4-amino-, 8-nitro-, or 8-hydroxyquinoline to prevent corrosion (74). 

Corrosion Inhibition. Another important property of antifreeze solutions is the corrosion protection they provide. Most cooling systems contain varied materials of constmction including multiple metals, elastomeric materials, and rigid polymeric materials. The antifreeze chosen must contain corrosion inhibitors that are compatible with all the materials in a system. Additionally, the fluid and its corrosion inhibitor package must be suitable for the operating temperatures and conditions of the system. 

See also Antioxidants Antifreezes and deicing fluids Antistatic agents Corrosion and corrosion inhibitors Industrial antimicrobial agents. 

Approximately 5% of the U.S. consumption of is in agriculture. Boron is a necessary trace nutrient for plants and is added in small quantities to a number of fertilizers. Borates are also used in crop sprays for fast rehef of boron deficiency. Borates, when apphed at relatively high concentration, act as nonselective herbicides. Small quantities of borates are used in the manufacture of alloys and refractories (qv). Molten borates readily dissolve other metal oxides usage as a flux in metallurgy is an important apphcation. Other important small volume apphcations for borates are in fire retardants for both plastics and ceUulosic materials, in hydrocarbon fuels for fungus control, and in automotive antifreeze for corrosion control (see Corrosion and corrosion inhibitors). Borates are used as neutron absorbers in nuclear reactors. Several borates, which are registered with the Environmental Protection Agency (EPA) can be used for insecticidal purposes, eg, TIM-BOR. 

Metal- Working and Hydraulic Fluids. In the preparation of fluids for metal-working and hydrauflcs, the trend has been to replace organic-based materials with aqueous-based materials. Neodecanoic acid has found apphcation in these newer fluids as a corrosion inhibitor and a viscosity improver. For example, neodecanoic acid is used in an aqueous hydrauflc fluid concentrate for corrosion inhibition and improved antiwear properties (101), in the preparation of a thickened aqueous hydrauflc fluid to reduce viscosity loss (102), and in a water-soluble metal working oil to reduce corrosion (103). In a similar vein, neodecanoic acid has been used in antifreeze concentrates for corrosion inhibition (104). 

Miscellaneous Derivatives. Fimehc acid is used as an intermediate in some pharmaceuticals and in aroma chemicals ethylene brassylate is a synthetic musk (114). Salts of the diacids have shown utUity as surfactants and as corrosion inhibitors. The alkaline, ammonium, or organoamine salts of glutaric acid (115) or C-5—C-16 diacids (116) are useflil as noncorrosive components for antifreeze formulations, as are methylene azelaic acid and its alkah metal salt (117). Salts derived from C-21 diacids are used primarily as surfactants and find apphcation in detergents, fabric softeners, metal working fluids, and lubricants (118). The salts of the unsaturated C-20 diacid also exhibit anticorrosion properties, and the sodium salts of the branched C-20 diacids have the abUity to complex heavy metals from dilute aqueous solutions (88). 

Soldered brass seldom gives trouble. In radiators, antifreeze solutions have been alleged to cause corrosion, possibly because materials such as ethylene glycol sometimes detach protective deposits. Sodium nitrite, valuable as a corrosion inhibitor for other metals in a radiator, tends to attack solders, but sodium benzoate is safe and, in addition, protects the soldered joint against the action of nitrites. In an investigation of other inhibitors in ethylene glycol solutions, 1% borax, either alone or in combination with 0-1% mercaptobenzothiazole, appeared to be satisfactory. 

It is also used as a corrosion inhibitor in automotive antifreeze products. 

Dibasic salts of dicyclopentadiene dicarboxylic acid are claimed to be active as corrosion inhibitors [444], Certain salts of fatty acids (metal soaps), together with benzotriazole, are claimed to give synergistic effects for corrosion in antifreeze-agent formulations [446]. 

The choice of a corrosion inhibitor as an additive in antifreezing agents is also dependent on the mode of operation. For instance, cars are operated intermittently. Here the corrosion inhibitors must also protect the system when it is idle. Film-forming silicates can protect the system while idle. This is especially true of aluminum parts, which are introduced in cars for the sake of weight reduction. But silicones can react with ethylene glycol to form crosslinked polymers. These gels may clog lines. 

Uses Stabilizing rubber latex solvent for albumin, casein, shellac, and sulfur neutralizing oils in antifreeze as a corrosion inhibitor emulsifier adhesives textile lubricants fungicides manufacturing chelating agents such as EOT A (ethylenediaminetetraacetic acid) dimethylol-ethylene-urea resins organic synthesis. 

Uses. Vulcanization accelerator for type of rubber usually used in the production of household rubber gloves rather than medical rubber gloves corrosion inhibitor in metal-working fluids, detergents, antifreeze, and photographic emulsions. 

Diethylene and triethylene glycol (DEG and TEG) are produced as byproducts of ethylene glycol. DEG and TEG are used in polyurethane and unsaturated polyester resins and in the drying of natural gas. DEG is also used in antifreeze and in the synthesis of morpholine, a solvent, corrosion inhibitor, antioxidant, and pharmaceutical intermediate. 

Ethylenediamine, as such, is used as a solvent for various compds, as a corrosion inhibitor in antifreeze soln, stabilizer in rubber latex, etc. Its use as a colorimetric reagent for expls, such as TNT, etc, is discussed in Vol 3 of Encycl, p C406 L Refs 1) Beil 4, 230, (398), [676] 1478 ... 

Industrial applications of corrosion inhibitors are too numerous to cover in the present context. The inhibitor industry amounts to several billion dollars annually. Applications of inhibitors in petroleum production, oil and gas wells and pipelines, potable water, water cooling towers, acid systems, automobile antifreeze systems, paints, boiler waters,... 

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