MXPA99007539A - Iminodiacetonitrile mirror back coating corrosion inhibitor - Google Patents

Abstract

A lead-free composition capable of being applied as a film andhardening to form a protective layer on the back of a mirror comprises a fluid organic resin and a corrosion inhibitior selected from a compound represented by formula (I) wherein the individual radicals R1, R2, R3 and R4 can be identical or different and are each hydrogen, an aliphatic, cycloaliphatic, araliphatic or aromatic radical, and can be substituted or unsubstituted;A is hydrogen or CZ-CR5R6CN;X, Y and Z are independently selected from 0-5;and R5 and R6 are as defined for R1, R2, R3 and R4 above. A preferred additive is iminodiacetonitrile wherein A is hydrogen;R1, R2, R3 and R4 are each hydrogen;and X and Y are 0. The organic resin may be any thermoplastic or thermosetting resin suitable for coating the reflective and other metallic layers of the mirror. Exemplary resins include alkyd resins, acrylic resins, modified alkyd resins, polyesters, urethane oils, vinyl halide polymers or copolymers, oleoresinous varnishes, nitrocellulose compositions, phenol-formaldehyde resin varnishes, and epoxy resins. Preferably, the resin is an alkyd or modified alkyd resin. The aforementioned corrosion inhibitor may be present in an amount about 0.01 to 20 weight percent, preferably 0.5 to 10 weight percent, of the organic resin coating system. The resin system should be essentially free of lead and lead salts. To inhibit the corrosion of metallic film layers on mirrors, a mirror having a glass substrate layer and metallic film layer thereover should be obtained, after which the fluid organic resin coating system containing the aforementioned corrosion inhibitor is applied over the metallic film layer. The organic resin coating system is then hardened to produce the protective coating layer over the metallic layer. Other articles having metallic surfaces may also be protected by the resin system containing the novel corrosion inhibitor of the present invention.

Description

INHIBITOR OF CORROSION OF IMINODIACETONITRIL COVER FOR REAR OF MIRRORS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a cover for use on the back of mirrors, and in particular, with an organic charge-free cover, which contains a compound containing a di or tri- nitrile, preferably iminodiacetonitrile or nitrilotriacetonitrilo, whose cover is applied to the layer of metal film on the back of a mirror, to protect the metal layer and prevent corrosion thereof. 2. Description of Related Art Typical mirrors are made of a sheet of glass and a thin layer of a metal film applied to the back of the sheet. The metal film layer adhered directly to the glass is usually a silver film, although other metal films, such as copper, can also be used. When silver is used as the primary reflective layer, it is commonly protected by a second layer of metallic copper film or some other metal. It has been known for a long time to use various paints and other organic film-forming resins, as another protective layer on a layer of metallic film to protect the layer against corrosion and physical damage. Traditionally, these paints have included lead-based corrosion inhibitors, such as lead salts. However, in recent times, both users and producers of such paint products have sought to eliminate the use of lead and lead compounds due to health and environmental reasons.

Numerous efforts have been made to remove the lead from the paints and / or otherwise increase the effectiveness and utility of the protective covers for metallic films for the back of the mirrors. A recent effort in this direction is reflected in U.S. Patent No. 4,707,405, to Evans et al., Directed to the use of cyanamide salts of non-lead metals as corrosion-inhibiting pigments in coatings for the backside of the Mirrors. This patent discloses the use of said non-lead cyanamide salts, such as calcium cyanamide, and zinc cyanamide, in various types of thermoplastic or thermosetting film-forming resins, which are applied to the silver and copper layers on the back of the mirrors. US Patents Nos. 5,248,331, and 5,252,402, to Sanford et al., Disclose a lead-free resin or paint composition for use as a cover for the rear of the mirrors, which contains as a corrosion inhibitor, dicyandiamide, salts of acids or metals thereof, hydrogen cyanamide, and 2-cyanoacetamide. U.S. Pat. No. 5,314,532 to Hughes et al., Discloses the use of salt-free, soluble, and non-contaminating antioxidant pigments, which are cyanamide derivatives of metals, and which are used in combination with organic resin polymers as protective coatings for the part back of the mirrors. The patent discusses the US patent of prior art no. No. 4,707,405, Evans, et al., Supra, which uses the same cyanamide salts of non-lead metals as a corrosion inhibitor in organic film-forming resins for covers for the back of the mirrors, the refinement being the use of "pure" salts. Accordingly, the pure salts contain less than about 0.5 weight percent soluble salts. U.S. Patent No. 4.255.214, from Workens, discovers a method to protect mirrors covered with silver and copper, against oxidation and corrosion, inactivating the metal cover before applying a protective organic cover. The silver-copper coating is inactivated by applying an effective amount of tolyltriazole to the metal surfaces before applying the protective organic coating. U.S. Patent No. 5,389,301, from Fenzi, discovers a lead-free anticorrosive resin formulation, which contains cyanoacetylurea to protect the backside of the mirrors. Japanese patents 5311485, 5311492, and 5311495 show processes for treating a noble metal, including silver, by electrolyzing the metal in an aqueous solution containing an organic compound, such as a minimum compound, or other nitrogen-containing compounds, such as EDTA, for increase the corrosion resistance of the noble metal. U.S. Patent No. 4,543,215, to Brunnmueller et al., Discloses new iminodiacetonitriles and their preparation. It is discovered that nitriles are useful as starting materials for the preparation of dyes, fungicides, and other materials including anticorrosion agents. The findings of the above patents are incorporated herein by reference. Taking into account the problems and shortcomings of the prior art, and the need felt for so long by the industry, it is therefore an object of the present invention to provide a lead-free, effective corrosion-inhibiting coating for covering the layer of metal film on the back of a mirror and other articles of manufacture. It is another object of the present invention to provide an organic film forming resin that incorporates a corrosion inhibitor that does not contain lead, which can be easily applied by existing techniques, to the back of the mirrors.

It is another object of the present invention to provide a lead-free paint for protecting thin layers of metallic silver and / or copper or other metal films against corrosion. It is yet another object of the present invention to provide an effective process for the inhibition of corrosion of metal film layers on mirrors, or other articles of manufacture. It is another object of the present invention to provide a mirror and other articles having effective protection of its metallic film layer, against the spraying of salts and other corrosion-causing compounds. Other objects and advantages of the present invention will be apparent without difficulty from the following description.

COMPENDIUM OF THE INVENTION The above objects and others, which will be apparent to those skilled in the art, are achieved in the present invention which provides in a first aspect, a composition comprising a paint or other fluid organic resin coating system, capable if applied as a film and hardened to form a protective layer, the resin additionally contains a corrosion inhibitor containing a compound containing di and / or tri-nitrile. The preferred compounds can be defined according to the formula: C - R '- C - C - N - C - I I CN CN (0 wherein the individual radicals R1, R2, R3, and R4 can be identical or different, and each is hydrogen, an aliphatic, cycloaliphatic, araliphatic, or aromatic radical, and can be substituted or unsubstituted; A is hydrogen, or CZ-CR5R6CN; X, Y, and Z are independently selected from 0-5; and R5 and R6 are as defined for R1, R2, R3, and R4 above. Iminodiacetonitrile is a preferred additive (IDAN), where A is hydrogen; R1, R2, R3, and R4 are each hydrogen; and X and Y are 0. The term "hardened" is used to mean that the coating system can be cured if the resins are thermostatic, or dried, if the resins are thermoplastic. The organic resins used in the cover system can be any thermoplastic or thermostatic resin suitable for covering a metallic layer, such as that which is on the back of a mirror. Exemplary resins include alkyd resins, acrylic resins, acrylic alkyd resins and other modified resins, polyesters, urethane oils, vinyl halide polymers or copolymers, oleoresin varnishes, nitrocellulose compositions, phenol-formaldehyde resin varnishes, and epoxy resins. Preferably, the resin is a modified alkyd or alkyd resin, for example, short chain, or a phenolic alkyd resin system. The corrosion inhibiting compounds may be present in an amount, by weight, of about 0.1 to 20%, preferably about 0.5 to 10%, based on the organic resin coating system (including resins, solvents, and other additives). Preferably, the organic resin coating system should be substantially free of lead and lead, either as corrosion inhibitors, or other components. To inhibit the corrosion of metallic film layers on mirrors, a mirror having a layer of glass substrate and a layer of metallic film thereon should be obtained, after which the coating system of Fluid organic resin containing one or more of the aforementioned corrosion inhibitors is applied to the metallic film layer. The organic resin cover system is then hardened to produce a protective cover layer on the metal layer. The preferred mirror article contains, in sequence, the glass substrate, the metal film layer (s) which may be silver and / or copper, or some other metal, and the hardened organic resin system as described above. Preferably, the mirror has a thin layer of silver film adhered directly to the glass layer as the reflective layer, a thin protective layer of a copper film on the silver layer, and the hardened cover system described above , directly on the copper film layer as the primary corrosion inhibiting layer. In addition, other articles having metallic surfaces can be protected by the resin systems containing corrosion inhibitor, and that do not contain lead, which are described above.

Description of the Preferred Embodiment (s) The metal film mirrors and layers on which the cover of the present invention has been found to be particularly useful, are those in which one or more layers of silver and / or copper films have have been applied to a glass substrate, although the cover can also be useful on film layers of other metals. Preferably, the mirror consists of a layer of glass substrate, and a layer of silver or reflective copper film applied to the back surface of the glass. If a silver film is applied directly to the glass, it is common to apply a second layer of copper film over the silver, to provide protection against corrosion and physical damage to the silver layer. Said layers of metal film are relatively thin, and of the class of approximately 700 angstroms for the silver layer, and approximately 210 anstroms for the copper layer. Said mirrors can be made by any of the processes known in the prior art. The glass surface to which the metallic film layer is to be applied is usually lightly polished and cleaned, and then sensitized with a solution of aqueous stannous chloride. The silver film layer can be deposited on the sensitized glass surface by one of many methods, such as the one described in Pat. No. 4,737,188 to Bahls, the disclosure of which is incorporated herein by reference, in which a N-methylglucamine reductant is used with ammoniacal silver nitrate and a strong base, such as sodium hydroxide in aqueous solution, which solution is sprayed and combined on the sensitized glass surface to deposit the silver film. Then, a copper film can be applied on the silver film by any of a variety of prior art processes, such as a galvanic process using aqueous suspensions of iron and copper powder, or by the disproportion of cuprous minerals on the silver surface. This last process is described in pat. No. 3,963,842, to Sivertz et al., the disclosure of which is incorporated herein by reference. In said process, a solution of cupric tetraammonium sulfate is reduced by combination with hydroxyamine sulfate, and then reacted with an activator-modifier, such as a mixture of citric acid or ethylene diamine and H2SO4, to form a copper film on the silver surface. An ammonia-free process for copper deposition by disproportion is shown in U.S. Pat. 5,419,926, from Soitys. The patents mentioned above are incorporated herein by reference.

The cover of the present invention to be applied on the metallic film layer of copper, silver, or other metal, is based on any suitable thermosetting or thermoplastic organic film forming resin. The thermosetting resins contemplated in the use in the present invention are those which require heat to effect curing, such as by infrared heating, although air drying resins are also included at room temperature. Suitable resins include alkyd resins, acrylic resins, polyesters, urethane oils, vinyl halide polymers or copolymers, oleoresin varnishes, nitrocellulose compositions, phenol-formaldehyde resin varnishes, epoxy resins, or combinations of such resins. Preferably, the resins employed in the present invention are modified alkyd or alkyd resins, such as acrylic-alkyd copolymers, in combination with a solvent, and other additives such as a pigment, if desired, to produce a resin coating system. Said alkyd resin systems can be modified with acrylics, urethanes, and polyurethanes, phenolics, and combinations of the foregoing. More preferably, the resins can be acrylic-alkyd copolymers and phenolic resins in combination. Amino crosslinking agents, such as melamine-formaldehyde resins, and / or urea-formaldehyde resins, can be included in the modified alkyd resin system or other system, to render the system curable by heat. Alternatively, metal dryers can be used in the system to make it air dry.

The resin system of the present invention should employ a binder resin that forms a suitable film and provides good adhesion to and on the aforementioned metal film layer (s). The system may employ a suitable solvent of the type normally used in the particular resin system, for example, in alkyd resin systems As modified and alkyd of the present invention, an ester such as propylene glycol monomethyl ether acetate, butyl acetate, or sodium butyl acetate may be employed. Preferably, the modified alkyd or alkyd resins comprise 20 to 50 weight percent of the system, more preferably 20 to 35 weight percent. The solvents or solvent combinations employed in this system are preferably 20 to 35 percent by weight of the system. The additives that are normally used in resin coating systems for this type of application can also be added in addition to the resins and solvent, for example, pigments (when it is desired to impart a color), and inert fillers such as calcium carbonate or barites; fluid additives; anti-staling agents to support any dense pigment particle; catalysts such as blocked or unblocked acids (when a thermosetting resin is used); surface active agents; anti-peeling agents, such as methyl ethyl ketoxime; and additives for other purposes. The aforementioned resin systems by themselves harden completely to form a film on a layer of metal film. In order to impart effective corrosion resistance for the metallic film layer, the present invention specifically contemplates the use of a compound that does not contain lead, represented by the following formula: R2 A 3, I I '4 1- c - C - N - C - C - R CN CN (U wherein the individual radicals R1, R2, R3, and R4 can be identical or different, and each is hydrogen, an aliphatic, cycloaliphatic, araliphatic radical, or aromatic, and can be substituted or replaced; A is hydrogen, or CZ-CR5R6CN; X, Y, and Z are independently selected from 0-5; and Rs and R6 are as defined for R1, R2, R3, and R4 above. A preferred additive is iminodiacetonitrile, where A is hydrogen; R1, R2, R3, and R4 are each hydrogen; and X and Y are 0. Another preferred additive is nitrilotriacetonitrile (NTAN), wherein A is Cz-CR5R6CN; X, Y, and Z are 0; and R1-R6 are all hydrogen. The nitrile corrosion inhibitors of the invention are well known compounds, and their method of preparation is likewise well known to those skilled in the art. U.S. Patent No. No. 4,543,215, supra, discloses, -iminodiacetonitriles and their method of preparation. The methods of preparation include reacting an aldehyde-cyanohydrin with an amino-nitrile. Other methods of preparation of the prior art discovered therein include reacting, -aminonitriles with a carbonyl compound in a first step, and treating the resulting mixture with hydrocyanic acid. The corrosion inhibiting additives may be employed in an amount, by weight, of from about 0.01 to about 25% of the resin coating system, although about 0.1 to about 10% is preferable. More preferably, a range of from about 0.1% to about 5%, eg, 5% to 1.5%, is employed. At higher amounts, in particular greater than 10%, the corrosion inhibitor becomes particularly susceptible to reaction with water, for example, any moisture present in the environment. If such higher amounts of the nitrile compound are employed in the resin coating system of the present invention, it is preferable that a waterproof cover or additional moisture is applied over the hardened resin cover. The corrosion inhibitors of the present invention can be combined with the resin system, by crumbling them into fine particles, generally up to about 50 microns, preferably from 10 to 40 microns, and more preferably, about 1 to 10 microns, e.g., 5 microns in size. It has been found that when the small size particles are used, a lower total weight percentage of the inhibitor is needed to achieve a desirable level of protection against corrosion, since the smaller particle size can be dispersed throughout the resin to a greater scope to provide the necessary protection. Alternatively, the corrosion inhibitor can be dissolved in a suitable solvent and dispersed and combined in the resin system. It is believed that corrosion inhibitors are substantially unreacted in the combined fluid resin system, and are available for inhibition of corrosion during or after application to the metal surface. While not wishing to be bound by theory, it is believed that the lead-free corrosion inhibiting compounds discovered herein, react in the present system to: 1) inactivate the metal film on which it is applied, for example, a copper film, and create a complex with the metal to reduce corrosion; 2) increase the adhesion of the metallic film, like copper, to the cured resin; or 3) a combination of 1 and 2 above. Corrosion inhibitors are incorporated instead of using conventional lead-based pigments, such as lead salts, used in the past. However, other corrosion inhibitors can be used in conjunction with the nitrile compounds, such as zinc oxide, to provide a desired degree of protection in a specific application. If desired, low amounts of leaded materials that comply with environmental laws and regulations can be added to the resin system. Preferably, the combined resin system to be applied over the metal films mentioned above is completely lead-free, to meet more easily with environmental laws and regulations in its manufacture and use. The composite resin system employing the non-lead corrosion inhibitors of the present invention is applied to the metal layers on the back of the mirror by conventional processes, such as air or non-air spraying (preferably the latter), cover by rollers, covered by curtain, screen printing or electrostatically. The thermosetting resin systems such as the aforementioned preferred modified alkyd or alkyd resin systems can be dried by infrared heating, the typical conditions being five minutes of heating time, with an exit film temperature of about 250 ° F ( 120 ° C). The thickness of the dried resin film layer can be up to 0.002 inch. (51 microns) thick, or higher, although it is preferable that the thickness of the film is from about 0.001 to 0.0015 inches. (25 to 38 microns) thick. When thicker covers are desired, multiple layers of the cover can be applied. The use of the thin layers described above allows the applied resin system to be quickly dried to a hardened layer, without causing bubbles or other defects. The resin system incorporating the corrosion inhibitors of the present invention provides good protection to the edges of the metallic film layers of the mirror, in which location corrosion usually begins. Corrosion of the edges of mirrors (also known as "black border") can occur due to moisture present in bathrooms or other high humidity environments. Other causes include the use of certain adhesives, in which a component (for example, adhesives based on acetic acid in silicone) can attack the resin cover layer and the metal film. Also, when the edges of the mirrors are beveled or polished With an abrasive, the abrasive cooler that has a high pH level can get over the edge and attack the layers of metal film and mirror paint. In addition to providing good protection against corrosion, the resin coating system employing the corrosion inhibitors of the present invention should be capable of providing a smooth finish having a good appearance, and, if the mirror is later cut or otherwise manipulated, you should avoid chipping the resin paint at the edges of the mirror.

The following non-limiting examples are provided to illustrate resin systems employing corrosion inhibitors of the present invention. A series of glass panels was cleaned, sensitized, and covered with successive layers of a silver film and a copper film according to the process described above. The resulting silver film layer was approximately 700 angstroms in thickness, and the upper layer of resulting copper film was approximately 220 angstroms in thickness. The silver was applied to the glass panels by a conventional spray system, and the copper was applied to the silver layer on a comparative basis, either by a galvanic system, or a cuprous disproportionation system.

EXAMPLE 1 To evaluate the effect of the claimed nitrile compounds as corrosion inhibitors, a commercial short oil alkyd based liquid resin coating system used as a base to prevent corrosion of the metal layer of mirrors was modified as it shows Next, in Table I, adding the observed additives to the system, at a concentration of 15 - 20 Ib / 100 gal (approximately 1, 4 - 1, 9% w / w). The density of the resin is approximately 11 Ib / gal. The liquid resin coating systems were applied to the copper layer on the back of the mirrored glass samples mentioned above, using a low drawn bar, and then subjected to infrared drying at approximately 250 ° F. (120 ° C) for approximately five (5) minutes, until they were cured to a hardened film layer of approximately 0.001 inch. (25 microns) thick. The covered mirror samples were then subjected to a corrosion test in a 20% salt spray environment, for 300 hours, according to federal specification DD-M-4411 B, and ASTM B-117-73. All additives were added to the resin coating system as commercially available powders.

TABLE 1 * TNTC = too numerous to count The results show that the additive numbers 1, 2, and 3 of the invention provided excellent corrosion inhibiting results.

EXAMPLE 2 The resin coating system of EXAMPLE 1 was used to show the effect of the concentration on the effectiveness of the additive of the invention. IDAN was sprayed at approximately 5 microns in particle size and was added to the system in concentration as shown in Table 2. A control using DCDA at 15 Ib / gal showed 0 black border (mm), and had a density of spots of 8.

TABLE 2 Additive Concentration Edge Failure (mm) Spot Density Ib. / gal 5 2 - 19 57 5 3 - 16 59 10 1 - 3 18 10 1 - 3 16 13 Stroke - 1 48 15 Stroke- 1 TNTC EXAMPLE 3 The following example shows the effect of particle size on the inhibitory effectiveness of IDAN corrosion. The resin cover system of EXAMPLE 1 was used, and the IDAN was added to each sample at a level of 10 Ibs / 100 gallon. The results are shown in Table 3.

TABLE 3 Edge Failure Particle Size (mm) Spot Density Lab Grinding Additive. Trazo-8 80 Grinding Pebble Mill Stroke- 11 26 Pulverizing Stroke- 1 15 Lab grinding is approximately 40 microns, grinding mill of pebbles of approximately 25 microns, and the spray of approximately 5 microns.

EXAMPLE 4 The following example shows the effect of both the additive level and the type of copper surface that is being protected, when IDAN is used in the resin formulation of Example 1. The IDAN had a particle size of about 5 microns . The results are shown in Table 4.

TABLE 4 Edge Failure (mm) Additive Level Ib / 100 Copper Galvanic Despro gal. 0 3-25 Total failure 0.01 3-30 Total failure 0.10 2-25 Total failure 1.0 1 -25 8-39 2.0 7-45 Stroke - 3 5.0 Stroke - 25 Stroke - 1 10 , 0 Stroke - 10 1 -15 15,0 1 -14 1 -15 Lead Control * Stroke - 5 10-37 Lead was used in the form of lead cyanamide at a level of 40 Ib / 100 gal.

EXAMPLE 5 The following example shows the effectiveness of different levels of IDAN in another commercial resin formulation, which is a resin coating system based on alkyd-phenolic resin used for the prevention of mirror corrosion. The results are shown in Table 5.

TABLE 5 Additive Level (Ib. / 100 Edge Failure (mm) Spot Density gal.) 1 -15 39 6 Stroke - 5 46 7 Stroke - 21/2 51 8 1 -5 52 9 Stroke - W? 52 10 Stroke - 2 42 Lead Control * 0-4 18 * Lead was used in the form of lead cyanamide at a level of 40 Ib / 100 gal.

EXAMPLE 6 Various metal corrosion resin systems were evaluated as in Example 1, to show the effectiveness of IDAN in different resin systems.

The results are shown in Table 6. TABLE 6 Resin System Edge Failure (mm) Density of Stains Linseed / Alquídica Tr-1 29 Phenoxy Trimite Castor Oil 6 Dehydrated / Acrylic Phenolic Acid - Alchemical 0-5 61 Alquídica Short Oil Tr-2 17 Flax Seed / Phenolic Tr-1 TNTC Castor Oil Tr-13 10 Dehydrated / Alquídica EXAMPLE 7 The following example shows the effectiveness of IDAN when evaluated according to Example 1.

TABLE 7 Additive Level (Ib. / 100 Edge Failure (mm) Density of Gal. Stains) 14 1 - 2 16 0 20 - 32 Total Fault Control (DCDA) Tr - 2 10 The aforementioned examples of resin systems including the corrosion inhibitors of the present invention can be further modified, for example, by including other pigments such as zinc oxide, or titanium dioxide, in replacement of part by talc, or by using resin additional part replacement for the pigments to achieve better corrosion resistance. In addition to the protection of mirror film layers, as described above, the resins containing the corrosion inhibitors of the present invention can be applied to, and on metallic surface layers, such as copper, copper-based alloys, silver, or silver-based alloys of other items to provide enhanced protection against corrosion. While the invention has been described with reference to specific embodiments, those skilled in the art will recognize that variations are possible without departing from the spirit and scope of the invention, and that it is intended to cover all changes and modifications of the invention. discovered in the present for purposes of illustration that do not constitute a departure from the spirit and scope of the invention. Having this form described the invention, what is claimed is:

Claims (51)

1. A composition for inhibiting the corrosion of a metallic film layer on the back of mirrors, comprising a fluid organic resin coating system capable of being applied as a film and hardening to form a protective layer on said film layer metal, said resin system comprising an organic resin, and a corrosion inhibitor in an amount, by weight, of about 0.01 to 20% represented by the formula: 1 A R3 I i R - c- c - N - _ c - C - I CN CN (I) wherein the individual radicals R1, R2, R3, and R4 can be identical or different, and each is hydrogen, an aliphatic, cycloaliphatic, araliphatic, or aromatic radical, and can be substituted or unsubstituted; A is hydrogen, or CZ-CR5R6CN; X, Y, and Z are independently selected from 0-5; and R5 and R6 are as defined for R1, R

2, R3, and R4 above. The composition of claim 1, wherein said corrosion inhibitor is present in an amount, by weight, of about 0.1 to 10% of said organic resin coating system.

3. The composition of claim 1, wherein said cover system is lead-free.

4. The composition of claim 1, wherein said corrosion inhibitor is present in an amount, by weight, of about 0.5 to 1.

5% weight percent of said organic resin coating system. The composition of claim 1, wherein said corrosion inhibitor is present in an amount, by weight, of about 0.1 to 10% of said organic resin coating system, and the particle size of the inhibitor of corrosion is up to approximately 50 microns.

6. The composition of claim 1, wherein said corrosion inhibitor is minodiacetonitrile.

The composition of claim 6, wherein said composition is essentially lead-free.

The composition of claim 1, wherein said corrosion inhibitor is nitrilotriacetonitrile.

The composition of claim 8, wherein said composition is essentially lead-free.

The composition of claim 1, wherein said organic resin coating system is selected from the group consisting of alkyd resins, modified alkyd resins, acrylic resins, melamine formaldehyde resins, urea formaldehyde resins, and combinations thereof .

11. The composition of claim 10, wherein said corrosion inhibitor is iminodiacetonitrile.

The composition of claim 11, wherein said composition is essentially lead-free.

13. The composition of claim 10, wherein said corrosion inhibitor is nitrilotriacetonitrile.

The composition of claim 13, wherein said composition is essentially lead-free.

15. A composition for inhibiting the corrosion of a metal surface, comprising a liquid organic resin coating system capable of being applied as a film and hardened to form a protective layer on said metallic surface, said resin system including an organic resin and a corrosion inhibitor in an amount of about 0.01 to 20 weight percent, selected from a compound represented by the following formula: A I, 1 _ c - C - N - C C - I CN CN (I) wherein the individual radicals R1, R2, R3, and R4 can be identical or different, and each is hydrogen, an aliphatic, cycloaliphatic, araliphatic, or aromatic radical, and can be substituted or unsubstituted; A is hydrogen, or CZ-CRSR6CN; X, Y, and Z are independently selected from 0-5; and R5 and R6 are as defined for R1, R2, R3, and R4 above.

16. The composition of claim 15, wherein said corrosion inhibitor is present in an amount, by weight, of about 0.1 to 10. % of said organic resin cover system.

The composition of claim 15, wherein said corrosion inhibitor is present in an amount, by weight, of about 0.5 to 1.5% of said organic resin coating system.

18. The composition of claim 16, wherein said corrosion inhibitor is iminodiacetonitrile,

19. The composition of claim 18, wherein said composition is substantially lead-free.

The composition of claim 16, wherein said corrosion inhibitor is nitrilotriacetonitrile.

The composition of claim 20, wherein said composition is substantially lead-free.

22. An article having a metallic surface and a protective covering layer on the metal surface, made of a hardened organic resin coating system, selected from the group consisting of alkyd resins, modified alkyd resins, acrylic resins, melamine resins formaldehyde, urea formaldehyde resins, and combinations of the above, incorporating a corrosion inhibitor represented by the formula: R A R "R - C - C - N - C C - I CN CN [i] wherein the individual radicals R1, R2, R3, and R4 can be identical or different, and each is hydrogen, an aliphatic, cycloaliphatic, araliphatic, or aromatic radical, and can be substituted or unsubstituted; A is hydrogen, or CZ-CR5R6CN; X, Y, and Z are independently selected from 0-5; and R5 and Rd are as defined for R1, R2, R3, and R4 above.

23. The article of claim 22, wherein said metal surface is made of copper or a copper-based alloy.

24. The article of claim 22, wherein said metal surface is made of silver or a silver-based alloy. 2

25. The article of claim 22, wherein said corrosion inhibitor is present in an amount of about 0.01 to 20 weight percent of said organic resin coating system.

26. The article of claim 22, wherein said corrosion inhibitor is present in an amount of about 0.1 to 10 weight percent of said organic resin coating system.

27. The article of claim 26, wherein said organic resin coating system is selected from the group consisting of alkyd resins, and modified alkyd resins.

28. The article of claim 26, wherein said corrosion inhibitor is iminodiacetonitrile.

29. The article of claim 26, wherein said corrosion inhibitor is nitrilotriacetonitrile.

30. A mirror comprising, sequencing, a layer of glass substrate, a layer of metal film adhered to the glass layer, and a protective cover layer adhered to the metal layer, made of an organic resin coating system hardened, incorporating a corrosion inhibitor represented by the formula: R A R l i I N - C C R - c - c I [I] CN CN wherein the individual radicals R1, R2, R3, and R4 can be identical or different, and each is hydrogen, an aliphatic, cycloaliphatic, araliphatic, or aromatic radical, and can be substituted or unsubstituted; A is hydrogen, or CZ-CRSR6CN; X, Y, and Z are independently selected from 0-5; and R5 and R6 are as defined for R1, R2, R3, and R4 above.

The mirror of claim 30, wherein said corrosion inhibitor is present in an amount of about 0.01 to 20% weight percent of said organic resin coating system.

32. The mirror of claim 30, wherein said metal film layer comprises one or more layers of a metal selected from the group consisting of silver and copper.

33. The mirror of claim 30, wherein said hardened cover layer is adhered to a layer of copper film.

34. The mirror of claim 30, wherein said hardened cover layer is adhered to a layer of silver film.

35. The mirror of claim 30, wherein said hardened cover layer is lead-free.

36. The mirror of claim 30, wherein said corrosion inhibitor is present in an amount of about 0.5 to 5 weight percent of said organic resin coating system.

37. The mirror of claim 30, wherein said organic resin coating system is selected from the group consisting of alkyd resins, modified alkyd resins, acrylic resins, melamine formaldehyde resins, urea formaldehyde resins, and combinations thereof. .

38. The mirror of claim 37, wherein said corrosion inhibitor is iminodiacetonitrile.

39. The mirror of claim 37, wherein said corrosion inhibitor is nitrilotriacetonitrile.

40. A process for inhibiting the corrosion of metal film layers on mirrors, comprising the steps of: to. obtaining a mirror having a layer of glass substrate and a layer of metal film adhered to the glass layer; b. Apply a fluid organic resin coating system containing a corrosion inhibitor represented by the formula: 3 R A R. , I I i F i _ c- C - N - C - C i "i [i] CN CN wherein the individual radicals R1, R2, R3, and R4 can be identical or different, and each is hydrogen, an aliphatic, cycloaliphatic, araliphatic, or aromatic radical, and can be substituted or unsubstituted; A is hydrogen, or CZ-CR5R6CN; X, Y, and Z are independently selected from 0-5; and R5 and Rd are as defined for R1, R2, R3, and R4 above; and c. hardening the resin system to produce a protective cover layer on said metallic layer.

41. The process of claim 40, wherein said resin system includes an organic resin selected from the group consisting of alkyd resins, acrylic resins, modified alkyd resins, polyesters, urethane oils, vinyl halide polymers or copolymers, oleoresin varnishes , nitrocellulose compositions, phenol-formaldehyde resin varnishes, melamine formaldehyde resins, formaidehyde urea resins, epoxy resins, and combinations of the foregoing.

42. The process of claim 40, wherein said corrosion inhibitor is present in an amount of about 0.01 to 20% weight percent of said organic resin coating system.

43. The process of claim 40, wherein said metal film layer comprises one or more layers of a metal selected from the group consisting of silver and copper.

44. The process of claim 40, wherein said hardened cover layer is adhered to a layer of copper film.

45. The process of claim 40, wherein said hardened cover layer is adhered to a layer of silver film.

46. The process of claim 40, wherein said hardened cover layer is lead-free.

47. The process of claim 40, wherein said corrosion inhibitor is present in an amount of about 0.5 to 5 weight percent of said organic resin coating system.

48. A process for inhibiting corrosion of a metal surface, comprising the steps of: a. get an item that has a metal surface; b. Apply a liquid organic resin system containing a corrosion inhibitor represented by the formula: R - C - C N - C C - CN CN [i] wherein the individual radicals R1, R2, R3, and R4 can be identical or different, and each is hydrogen, an aliphatic, cycloaliphatic, araliphatic, or aromatic radical, and can be substituted or unsubstituted; A is hydrogen, or CZ-CR5R6CN; X, Y, and Z are independently selected from 0-5; and R5 and R6 are as defined for R1, R2, R3, and R4 above; and c. hardening the resin system to produce a protective cover layer on said metal surface.

49. The process of claim 48, wherein said metal surface is made of copper or a copper-based alloy.

50. The process of claim 48, wherein said metal surface is made of silver or a silver-based alloy.

51. The process of claim 48, wherein said corrosion inhibitor is present in an amount of about 0.01 to 20 weight percent of said organic resin coating system. SUMMARY OF THE INVENTION A lead-free composition capable of being applied as a film and hardened to form a protective layer on the back of a mirror comprises a fluid organic resin and a corrosion inhibitor selected from a compound represented by the formula: R * A, i l R1- C- C - N - C i% and CN CN (1) wherein the individual radicals R1, R2, R3, and R4 can be identical or different, and each is hydrogen, an aliphatic, cycloaliphatic, araliphatic, or aromatic radical, and can be substituted or unsubstituted; A is hydrogen, or CZ-CR5R6CN; X, Y, and Z are independently selected from 0-5; and R5 and Rd are as defined for R1, R2, R3, and R4 above. A preferred additive is iminodiacetonitrile, wherein A is hydrogen; R1, R2, R3, and R4 is each hydrogen; and X and y are 0. The organic resin can be any thermoplastic or thermostatic resin suitable for covering the reflecting layers and other metallic layers of the mirror. Exemplary resins include acrylic resins, acrylic resins, modified alkyd resins, polyesters, urethane oils, vinyl halide polymers or copolymers, oleoresin varnishes, nitrocellulose compositions, phenol-formaldehyde resin varnishes, and epoxy resins. Preferably, the resin is a modified alkyd or alkyd resin. The aforementioned corrosion inhibitor may be present in an amount of about 0.01 to 20 weight percent, preferably 0.5 to 10 weight percent, of the organic resin coating system. The resin system It should be essentially free of lead and lead salts. To inhibit the corrosion of metal film layers in mirrors, a mirror having a layer of glass substrate and a layer of metal film thereon should be obtained, after which the fluid organic resin coating system containing the inhibitor of the aforementioned corrosion is applied on the metallic film layer. The organic resin cover system is then hardened to produce the protective cover layer on the metal layer. Other articles having metal surfaces can be further protected by the resin system containing the new corrosion inhibitor of the present invention.