Compositions: coating or plastic – Coating or plastic compositions – Corrosion inhibiting coating composition
Patent
1993-06-17
1995-03-21
Green, Anthony
Compositions: coating or plastic
Coating or plastic compositions
Corrosion inhibiting coating composition
106 1442, 106 1444, 521 50, 521 56, 521134, 521145, 523218, 523200, C08K 716, C08J 918, C08J 922
Patent
active
053991893
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns an anti-corrosive protective composition for metal. The composition contains a curable binder, which after curing has low-water and oxygen permeability, and at least one filler composed of solid parts.
Such compositions are used to avoid or to slow down the oxidation of easily oxidizable metals, especially iron and steel. These compositions are applied in a liquid or powder form and harden on the metal's surface.
Rust formation on iron and steel is mainly the result of the formation of innumerable anodes and cathodes on the surface of the metal when it is exposed to oxygen and moisture.
We can find an example of the formation of microbatteries on metal surfaces which are only partly protected and are therefore unequally subjected to the influence of weather-circumstances. On the parts with a high oxygen concentration, cathodes are formed. On the parts with a low oxygen concentration, anodes are formed. The present electron theory shows that these microbatteries are the cause of corrosion. An electrochemical tension appears between the electrodes, so that hydrogen is formed at the cathodes while iron dissolves at the anodes.
The most obvious protection against corrosion consists of the application of a water- and gas impermeable coating on the metal surface. This principle of metal protection is known as the "barrier effect," and all existing anti-corrosive compositions are in a certain way based on this "barrier effect."
The fillers are know compositions of the preceding kind and are inert or mostly active pigments. Active pigments, materials which form combinations with oxygen and moisture to slow down the noxious influence of oxygen and moisture on the metal, improve the protection. These active pigments are mostly composed of lead, chromium, barium, molybdenum, zinc, calcium, strontium or phosphates. The activity of these pigments is limited in time, among other things, because of their reaction with water and oxygen. Moreover, most of these pigments are harmful for the environment, therefore their use will be increasingly limited.
Inert or active pigments are the classic pigments. Although, there is a preference for lamellar and inert materials such as aluminum silicate, magnesium silicate, magnesium aluminium silicate, iron-magnesium aluminium silicate, aluminium powder, zinc dust, barium sulphate, quartz, iron oxide, ritanium dioxide, etc.
Some of these minerals can already be treated with polymers, such as epoxy or silanes, in order to obtain better adhesion to the binder.
These minerals have sufficient water- and gas impermeability. However, if the adhesion of the binder on their surface is not good, a space is formed in which water accumulates, forming the so-called water bags. To prevent the formation of such water bags, thus preventing the permeability of the coating, some minerals are consequently treated.
Besides these pigments the known compositions usually contain other fillers, namely to reduce cost and possibly some solvents which facilitate the application of the coating on the metal surface.
It is generally accepted that a good anti-corrosive protective coating should be as dense as possible. In other words, any hollow space, no matter how small, should be avoided as these spaces drastically reduce the protective quality of the coating.
In order to obtain these properties, the known compositions are composed of a very strong ramificated polymer binder which adheres remarkably, preferably to fillers treated with adhesion promoters. Thus, the formation of hollow spaces in the cured coating is avoided at all costs. To prevent porosity in the coating, pigments and fillers are added in a lower volume concentration than the binder. In other words, the pigment volume concentration is lower than the critical pigment volume concentration of the composition.
The good, anti-corrosive, protective compositions, which are known, are therefore relatively expensive.
The object of the present invention is to remedy this disadvantage and to supply an anti-corrosive protectiv
REFERENCES:
patent: 4148955 (1979-04-01), Breitenfellner et al.
patent: 4185000 (1980-01-01), Gebauer et al.
patent: 4307142 (1981-12-01), Blitstein et al.
patent: 4318998 (1982-03-01), Berglund
patent: 4374874 (1983-02-01), Blitstein et al.
patent: 4403048 (1983-09-01), Blitstein et al.
World Patents Index Latest, Section Ch, Week 8547, Derwent Publications Ltd., Oct. 1985.
GEHA, naamloze vennootschap.
Green Anthony
LandOfFree
Anti-corrosive protective composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Anti-corrosive protective composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Anti-corrosive protective composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1146342