Anti-corrosion paint for steel with polyaniline

Details Anti-corrosion paint for steel with polyaniline Anti-corrosion paint for steel with polyaniline

2002-09-03

2004-06-29

Tucker, Philip (Department: 1712)

Stock material or miscellaneous articles

Composite

Of epoxy ether

C428S413000, C428S414000, C428S418000, C428S423100, C428S464000, C428S523000

Reexamination Certificate

active

06756123

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an anticorrosion paint which employs polyaniline as an anticorrosion pigment, so as to prevent the corrosion of metal materials, in particular, of steel materials. More specifically, the present invention relates to an anticorrosion paint, which can provide persistently excellent anticorrosion effect without using metal which causes environmental pollution.
BACKGROUND ART
As generally known in the art, the corrosion of metal materials including steel is a serious problem in various industrial fields. The corrosion of steel brings enormous loss in property and industry, and half of steel production is consumed in replacing the corroded steel structures every year. Various anticorrosion paints have been used to prevent the corrosion of metal materials, especially steel materials.
The above-mentioned anticorrosion paint is composed of metal, which is utilized as general anticorrosion pigment, and organic polymeric resins/inorganic resin which makes the metal to adhere to the surface of steel and protects coated object from corrosive environments. The anodizing forming type using Pb, Cr and the like, and the sacrificial anode anticorrosive type using Zn have been previously used as anticorrosion pigments.
However, the anodizing forming type anticorrosion pigments are classified as heavy metal, and so have the defect of causing another environmental problem at the time of elution, and the sacrificial anode anticorrosive type anticorrosion pigments exert an anticorrosion capability with an electrochemical sacrificial mode using the ionization tendency of the anticorrosion pigment, so have a defect of being unable to protect metal materials from corrosion for long period of time because the capability of the sacrificial anode anticorrosion decreases as the corrosion of sacrificial metals increases over time.
Since the rust of metal materials results from the action of air, water or carbon dioxide, the anticorrosion paints should perform two actions: to prevent them from contacting the surface of metal materials and block chemically the generation of the rust. A paint for primer coat should have particularly strong adherence to a metal basis and a paint for top coat should not permeate any air or water through the coating of paint, the low occurrence of cracking, high durability and high weatherability.
The oil based paints, which contain the mixed drying oil and the anticorrosion pigment, and the red lead paints, which contain the mixed red lead (Pb
3
O
4
) and boiled oil, are mainly used as anticorrosion paints. The anticorrosion paints that can substitute for the red lead paints comprise zinc powder, lead suboxide, basic zinc chromate (zinc yellow), or basic lead chromate (zinc chromide) pigments, in which the latter two pigments have a chemical anticorrosion effect. Besides, the anticorrosion paints may contain iron oxide, Bengala alone, or zinc yellow and red lead as combination pigments. As vehicles, those suitable for the primer coat or topcoat paints are used, and oil varnish and synthetic resin varnish as well as boiled oil are usually used. Recently, the paint, in which basic zinc chromate, phosphoric acid and butyral resin are dispersed into a mixed solvent of alcohol, ketone and water, is used for anticorrosive treatment of metal materials including aluminum, zinc or tin.
However, the prior anticorrosion paints as described above have problems such as the environmental pollution or low persistence of the anticorrosion effect.
Meanwhile, polyaniline is known as a material hard to handle because it is insoluble and difficult to be dispersed, despite its excellent function, it has many limits in its application. A recent technical development is capable of dispersing polyaniline into a matrix resin and permits its application in various fields and the development of products using it, but any application to the anticorrosion paints has not been reported.
DISCLOSURE OF THE INVENTION
Accordingly, the present invention is made to solve the problems of the prior art and the object of the invention is to provide anticorrosion paints for steel using polyaniline which has an excellent anticorrosion effect, long persistence of the anticorrosion effect, high durability and superior coating property controlling the anticorrosion effect, without using metals which cause environmental pollution as an anticorrosion pigment.
Another object of the present invention is to provide a method of simply preparing the anticorrosion paint.
To accomplish the above objects and other objects which can easily follow upon the above objects, the present invention provides a coated steel substrate comprising an anticorrosion paint system, wherein the paint system comprise a primer coat paint layer and a top coat paint layer: a primer coat paint layer including 3 to 49 weight percent (wt %) of the polyaniline, 40 to 86 wt % of the matrix resin, 1 to 47 wt % of the additives and 10 to 56 wt % of the mixed solvent; and a top coat paint layer for protecting for protecting the primer coat paint layer and improving the anticorrosion effect, the top coat paint layer including 40 to 89 wt % of matrix resin, 5 to 54 wt % of colored pigment, 1 to 50 wt % of additives and 5 to 54 wt % of mixed solvent.
Also, the anticorrosion paint of the present invention is characterized in that it uses no metal which has mainly been used in the prior arts as an anticorrosion pigment to solve the defects of the previous anticorrosion paint, and it uses polyaniline with an excellent anticorrosion function as the anticorrosion pigment to provide excellent anticorrosion effect on metal materials, particularly steel materials.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will hereinafter be described in further detail regarding the anticorrosion paint for steel using the polyaniline according to the preferred embodiments of the present invention.
Generally, the polyaniline is classified into a fully oxidized type, a partially oxidized type and a reduced type depending on an oxidation degree. Although the emeraldine base form of polyaniline (PANI-EB) is in an insulated state, it is transferred to the emeraldine salt form of polyaniline (PANI-ES) in a conductive state by doping the PANI-EB in protonic acid, such as hydrochloric acid. Electric conductivity is changed by doping level, the used organic solvent, and the kind of dopant or molecular weight. By improving doping level, the insulator-metal transition phenomenon occurs. The PANI-ES plays a role as a charge carrier by the formation of polaron that has a mobile defect in one-dimensional chain structure.
Emeraldine salt (electric conductivity: ~5 S/cm) is synthesized in powder form by oxidatively polymerizing aniline monomer using oxidants, such as ammonium peroxydisulfate(APS; (NH
4
)S
2
O
8
) in protonic acid solution including 1M hydrochloric acid(HCl). The emeraldine salt is transferred to the insulating emeraldine base (electric conductivity: ~10
−10
S/cm) by deprotonation in basic solution, such as ammonium hydroxide(NH
4
OH).
Since both forms of polyaniline (base and salt thereof) were not dissolved in solvent, they have been difficult to be fabricated, but after it was reported in 1986 that N-methyl-2-pyrrollidinone could be used as solvent, the polyanilines became to be fabricated into film, fiber or elastomer. When the film or fiber was stretched four times and then doped with 1M HCl, it represented an electrical conductivity of 220 S/cm. The degree of cross-linking is controlled by varying the molecular weight of the polyaniline used for fabrication of the film, the use of solution or the evaporation rate of the solvent, and the resultant diverse films represent various results in crystallinity, electric conductivity after doping, an electric conductivity mechanism and electromagnetic interference shielding capability.
Recently, since the polyaniline doped with the functional acid like camphorsulfonic acid or dodecylbenzenesulfonic acid is known to have an increased solubility in nonpolar or mild p

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