Releasable corrosion inhibitor compositions

Abstract

A new class of releasable corrosion inhibiting materials for protective coatings, methods of making the same, methods of using the same, and coatings containing the same are provided. The materials comprise one or more corrosion inhibitors that are chemically anchored to the surface of a particle having an aluminum oxyhydroxide surface through a carboxylate bond. The carboxylate / aluminum-oxyhydroxide-surface bond breaks under corrosion-causing conditions (for example the presence of high levels of hydroxide ions generated by the cathodic oxygen reduction reaction on metals such as iron and aluminum) thereby allowing the corrosion inhibitors to detach from the particle surface when corrosion is present.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application takes priority to U.S. patent application Ser. No. 10 / 171,402 and U.S. patent application Ser. No. 10 / 171,422, both filed on Jun. 12, 2002, both of which are incorporated by reference to the extent not inconsistent with the disclosure herewith.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] This invention was made, at least in part, with funding from Navy Contract No. N00014-96-0147, and Air Force Contract No. F33615-99-C-5013. The United States government may have certain rights in the invention.FIELD OF THE INVENTION [0003] This invention relates generally to compositions of matter and methods of preparation of surface modified aluminum oxyhydroxide particles that release one or more types of corrosion inhibitors when triggered by corrosion products. Corrosion inhibitors are anchored to the particles through a carboxylic acid. Hydroxide ions generated from the corrosion of metals triggers releas...

AI Technical Summary

Benefits of technology

[0030] The present invention also allows multiple types of corrosion inhibitors to be incorporated into a protective coating, preferably at concentrations sufficient to inhibit corrosion without degrading the physical properties and performance of the coating, either by adding particles having several different types of corrosion inhibitors chemically anchored to the particle surface or by adding several types of particles, each with a different type of corrosion inhibitor chemically anchored to the particle surface to the coating. This approach allows corrosion inhibitors that act via different mechanisms and at different pHs to be incorporated into the coating via the particles so that different types of corrosion inhibitors can be released to the corrosion site.

[0035] As used herein, an “anchor” is a carboxylate group that chemically bonds to the surface of the particle. As used herein “particle” or a “particle having an aluminum oxyhydroxide surface” includes particles of aluminum oxyhydroxide (for example, boehmite or pseudoboemite), particles that have a surface of aluminum oxyhydroxide and a core of a different substance, and particles that can form a surface of aluminum oxyhydroxide. “Surface” does not necessarily indicate a uniform layer of material is present. For example, there may be portions with no material, or the surface may be unevenly thick. When a corrosion inhibitor is “grafted” or “attached” or “anchored” or “chemically anchored” to a carboxylate group anchored to the aluminum oxyhydroxide surface, there may be one or more intermediate groups between the corrosion inhibitor and the carboxylate group, or the corrosion inhibitor may be directly chemically grafted (i.e., one bond) to the anchored carboxylate group. The intermediate groups may be bifunctional, i.e., contain a different reactive group on each end, or may be difunctional, i.e., contain the same reactive group on each end. “Corrosion inhibitor” is a structure that includes at least one portion that reduces at least one effect of corrosion.

Problems solved by technology

Corrosion has led to bridge collapses, fatal airplane and train crashes, and the leakage and subsequent explosion of natural gas pipelines.

Structures such as storage tanks, pipelines, ships, railcars, and tanker trucks, which store and / or transport hazardous materials can be weakened and made unsafe by corrosion, and corrosion is also the leading cause of leaking chemical storage tanks.

However, this approach is defeated if the coating has a defect, if the coating becomes damaged or simply if water or other corrosive agents slowly penetrate through the intact coating.

Unfortunately, soluble chromate corrosion inhibiting additives have adverse environmental effects, and there is a widely recognized need for non-chromate corrosion inhibitors.

Removing chromate-inhibited coatings by chemical or mechanical means also generates a hazardous chromated waste that requires expensive disposal.

Although there are numerous organic compounds that are excellent corrosion inhibitors in solution (V. S. Sastri, Corrosion Inhibitors: Principles and Applications, John Wiley and Sons, Chichseter, England 1998), these materials have yet to find widespread use in protective organic coatings.

These same functional groups, can unfortunately, also react with the polymer resins used to produce the coating.

Even if the organic corrosion inhibitors are designed so that they would not be locked into the polymer structure (e.g. using latent reactive groups), when the corrosion-inhibited coatings are exposed to water (e.g. rain or aqueous detergent solutions used to clean the coatings), the inhibitors can be lost from the film by leaching, migration or extraction.

The loss of inhibitor reduces the effectiveness and useful service lifetime of the coating.

However, to work, the corrosion inhibitor must be able to diffuse through the coating to reach the corrosion site; especially if a hole or a scratch in the coating produced the corrosion site.

Unfortunately, it is this mobility that allows the corrosion inhibitor to escape from the coating.

Furthermore, if the coatings contain toxics (as do the currently used chromated epoxies), the toxics can be leached into the environment.

In addition, adding a high concentration of a corrosion inhibitor to a coating can change the physical properties and chemical properties of a coating, often for the worse.

This reduces the effectiveness of the inhibitor and the effective service life of the coating.

However, the above patents do not disclose the use of carboxylate surface-modified aluminum oxyhydroxide particles or inorganic (non-aluminum oxyhydroxide) particles whose surfaces are coated with an aluminum oxyhydroxide and then carboxylate surface modified that provide for the triggered release of corrosion inhibitors

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