Stable acid inhibitor formulations with improved performance, lower toxicity and minimal environmental issues

Abstract

Aqueous concentrates of non-toxic corrosion inhibitors, preferably storage-stable, useful in acidic cleaning solutions for cleaning the surfaces of metal that contacts food or potable water, the concentrates comprising at least one polymer, which may be protein-derived or synthetic; at least one iodine ion providing compound; an acidifier; and optionally, at least one anionic, nonionic or amphoteric surfactant; at least one coupling agent; and a pH adjuster; the concentrates being substantially free of nonylphenol derivatives and compounds containing elemental iodine and providing an improved acid inhibition and less foaming than similar compositions comprising nonylphenol derivatives and elemental iodine when mixed with aqueous acidic cleaners; acidic solutions prepared therefrom; and methods of their use.

Description

FIELD OF THE INVENTION [0001] This invention relates to corrosion inhibitors for use in acidic cleaning and pickling compositions. More particularly, the invention relates to storage-stable aqueous concentrates for non-toxic corrosion inhibitors useful in acidic pickling solutions for cleaning the surfaces of metal used in potable water wells, cooling towers, food process equipment and electrolysis membranes and other units holding, delivering or otherwise coming into contact with, food or potable water. BACKGROUND OF THE INVENTION [0002] Water wells containing potable water require periodic cleaning in order to remove scale from the well casings, well screens, pump bowls, etc. Typically, this scale is removed using an acid solution, generally a solution of hydrochloric acid. However, when such acid cleaning agents are used, several of the components forming the pumping mechanism are subject to attack by the acid, in particular, the well screen which is usually made of 304 stainless...

AI Technical Summary

Benefits of technology

[0007] In an attempt to develop acid inhibitors useful in acid cleaners that do not contain elemental iodine and nonylphenol derivatives, Applicants unexpectedly discovered a new formulation that performed better than formulations taught by the '149 patent. The new formulation when mixed with an aqueous acidic cleaner provides greater protection against corrosion of metals exposed to the cleaner. The new formulation also causes less gassing off of iodine containing fumes and less undesirable foaming of the cleaner bath.

[0010] It is also an object of the invention to provide an aqueous acid inhibitor concentrate that has improved stability when exposed to temperatures colder than (−4 or 10 deg. C.) and hotter than (49 deg. C.) room temperature (21 deg. C.). It is a further object of the invention to provide an aqueous acid inhibitor concentrate having improved freeze / thaw stability, that is upon re-warming to room temperature after freezing, the concentrate shows little or no separation that cannot be eliminated by mixing.

[0015] In another embodiment of the invention the aqueous, corrosion inhibitor concentrate, comprises at least one polymer, which may be protein-derived or synthetic; at least one iodine ion providing compound; optionally, at least one anionic, nonionic or amphoteric surfactant; optionally, at least one coupling agent; and an acidifier; said concentrate comprising less than 1.0 wt % nonylphenol derivatives and less than 0.1 wt % of compounds containing elemental iodine, wherein said concentrate provides greater metal corrosion protection in acid cleaner solutions than a substantially identical concentrate containing amounts of nonylphenol phenol or its derivatives greater than or equal to 1.0 wt % and amounts compounds containing elemental iodine greater than 0.1 wt % . Preferably the polymer is a protein-derived polymer and the at least one iodine ion providing compound is a salt containing iodide anion. In a further aspect of this embodiment, the aqueous corrosion inhibitor concentrate comprises: about 1 to about 50% by weight of a gelatin hydrolysate; about 0.1 to about 15% by weight of ethylene diamine dihydroiodide; optionally, about 1 to about 20% by weight of at least one surfactant selected from the group consisting of anionic, nonionic, and amphoteric surfactants; optionally, at least one coupling agent; and from about 0.5 to about 5% by weight of an acidifier. In a preferred embodiment according to this further aspect, the concentrate further comprises a pH adjuster comprising at least one alkaline source, said aqueous corrosion inhibitor concentrate having improved shelf life as compared to a substantially identical concentrate prepared in the absence of said alkaline source.

Problems solved by technology

However, when such acid cleaning agents are used, several of the components forming the pumping mechanism are subject to attack by the acid, in particular, the well screen which is usually made of 304 stainless steel, the well casing which is usually made of mild steel, and especially the pump bowl which is usually cast iron.

The hydrochloric acid is usually present in the cleaners in a concentration range of from 10 to 20% by weight, which, upon repeated use, can be quite damaging to the above parts.

The use of toxic inhibitors is, of course, quite undesirable, while the use of gelatin alone is also unsatisfactory due to the difficulty of dissolving the gelatin in the cold water and the fact that the gelatin may not protect the metal parts of the well properly, especially the cast iron pump bowl.

The use of elemental iodine and nonylphenol derivatives is becoming less attractive to customers due to environmental, health and safety issues.

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