TECHNICAL FIELD

The present invention belongs particularly to hot-dip galvanizing process technical field, and relates to a coating composition which comprises zinc and which is resistant against red rust formations on surface and on edge cutting regions, and a flat steel coated with said coating composition.

PRIOR ART

Rust is a chemical formation, and is a general term used for iron oxides, generally red oxides, which are formed by chemical reaction of iron and oxygen in the mediums where humidity or water exists. There can be various types of rusts. Some rust types can be seen with the naked eye only in a few numbers of formations, and therefore, this is a dangerous condition particularly for industrial products.

Iron-based industrial products have very widespread usage areas in our daily lives. Therefore, protection of iron against rusting is a very important issue in terms of economy. Rust permeates air and water, therefore, abrasion continues not only on the surface of iron but also at the inner sides of iron. Therefore, in order to prevent dangers which result from rust, rust must be prevented from being formed beforehand.

Rusting can be prevented by dyeing, oiling or coating with another metal in the technical field. One of the most frequently used methods in this field is the method of coating with metals, and particularly in coating of iron, other metals like chrome, nickel, tin, etc. can be used.

Another method used for preventing rust is galvanizing process which is an electrochemical process. Zinc is used as the coating material in galvanizing processes. Because the costs of zinc are low, zinc adheres to the steel well, and zinc provides cathode protection for steel in case the zinc layer is damaged. Coating, used in galvanizing process, becomes useless in cases where the coating is torn, for instance when a hole or scratch occurs at the connection points for iron-based materials. Therefore, studies continue for adapting the coating materials, which are to be used in galvanizing processes, in accordance with the needs of today.

In the related technical field, even if rust protection is provided for the surfaces of iron-based products by means of traditional galvanizing process compositions, rust formation cannot be prevented on connection regions, particularly on edge cutting regions of said products with the desired high performances.

As a result, it is considered that a galvanizing process coating composition is needed to be obtained which has high-efficiency resistance against rust formation on surface, on connection and cutting regions of iron-based industrial products.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a galvanized coating composition which is suitable for use particularly in hot-dip galvanizing process and which provides high corrosion resistance effect, and a product which includes said coating composition.

The technical problem, determined by the present invention for the related technical field, is that the iron-based industrial products do not have corrosive resistance with desired values particularly in assembly, connection and cutting regions. Accordingly, an object of the present invention is to provide a galvanized coating composition for iron-based industrial products, which provides obtaining of higher salt fog surface rust hour for the same coating thickness than the conventional galvanized coatings used in the present art, and a product which includes said coating composition.

Another object of the present invention is to provide a galvanized coating composition for iron-based industrial products, which provides obtaining of higher salt fog edge cutting rust hour for the same coating thickness than the conventional galvanized coatings used in the present art. In one perspective, the present invention relates to the product coated with said galvanized coating composition.

The object of the present invention is to provide flat steel coated with a galvanized coating composition which is resistant against red rust formations on surface and on edge cutting regions and which is applicable to industry and which is suitable for mass production. In order to realize all these objects, the present invention is a product where a galvanized coating composition which is the coating material in flat steel galvanized coating processes is applied and which is suitable for use in hot-dip and/or continuous galvanizing processes, characterized in that said coating composition has salt fog test values which are compliant to ASTM B117 standards for at least 900 hours, and comprises aluminum component at a value between 0.17% and 0.22% by weight and magnesium component at a value between 0.5% and 1% by weight and zinc component for the remaining part.

In a possible embodiment of the present invention, the coating composition comprises aluminum component at a value of 0.18%, 0.19%, 0.2% or 0.21% by weight.

In a possible embodiment of the present invention, the coating composition comprises magnesium component at a value of 0.6%, 0.7%, 0.8% or 0.9% by weight.

In a possible embodiment of the present invention, the coating composition comprises magnesium at a value between 0.7% and 0.9% by weight, aluminum at a value between 0.18% and 0.2% by weight and zinc for the remaining part.

In a possible embodiment of the present invention, the coating composition comprises magnesium at a value between 0.8% and 0.85% by weight, aluminum at a value between 0.185% and 0.195% by weight and zinc for the remaining part.

BRIEF DESCRIPTION OF THE FIGURES

In Figure 1 , the views of salt fog test by means of raised hours between the traditional galvanized coating composition and 0.83% Mg+0.19% Al galvanized coating composition subjected to test are given.

In Figure 2, the edge sectional views of salt fog test by means of raised hours between the traditional galvanized coating composition and 0.83% Mg+0.19% Al galvanized coating composition subjected to test under the same standard conditions are given.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a galvanized coating composition which is suitable for use in galvanizing process and which provides high corrosion resistance effect, and a product comprising said coating composition. In the invention, “iron-based industrial products” mean the materials whose matrix mostly comprises iron metal. In the invention, as this material is preferably steel material, and if preferred, it can represent various cast iron materials, iron-based alloys, and iron-based composite and super alloys. In the invention, it must be known that the parts, which are described only as products, mean “iron-based industrial products”.

In the invention, “iron-based industrial products” mean iron-based alloyed pot as the most specific example. However, the protection scope of the present invention is not limited with iron-based alloyed pot and can cover various iron-based materials.

In the invention, “galvanizing process” is the coating of materials with zinc or zinc-including compositions by means of various process types. Said galvanizing process is realized for increasing corrosion resistances of materials.

In the invention, “hot-dip galvanizing process” means the process of immersing and removing of an iron-based material to the pools which are full of liquid zinc-based composition. Said processes are conducted at melting temperature of zinc.

In the invention, “coating thickness” means the amount of coating composition obtained on the iron-based material as a result of galvanizing process. Coating thickness is shown with pm unit.

In the art, it is known that as the coating thickness increases, anti-corrosive activity of the material surfaces increases, however, there are coating thicknesses applied for each different material surfaces. The innovative characteristic of the present invention is that the subject matter has anti-corrosive activity which shows higher performance when compared with coating compositions which have the same coating thickness as in the present art for iron-based industrial products.

In the invention, “red rust hour” is the hour where red rust appearance is obtained in salt fog tests conducted for showing anti-corrosive activity of the protective coating which exists on the material. In the invention, the salt fog corrosion tests have been realized in a compliant manner to ASTM B117 standards. The subject matter coating composition shows high performance anti-corrosive effect on connection, assembly and cutting regions of iron-based industrial products than the coatings which provide anti-corrosive characteristic and which exist in the technical field. In the invention, the term “h/pm” describes the red rust hour as a result of salt fog test per the amount of coating which exists on the material. In the invention, in order to evaluate materials which have different coating amount, evaluations have been made by calculating red rust hour per unit coating thickness.

The subject matter coating composition has a composition whose matrix is formed by zinc. Zinc is positioned on iron-based industrial product and enters into reaction with oxygen and prevents reaction of the iron-based industrial product with oxygen and prevents rust formation.

The subject matter coating composition comprises zinc metal and besides, it comprises aluminum metal with determined amount. The subject matter coating composition comprises aluminum at a value between 0.17% and 0.22% by weight. Preferably aluminum exists at a value of 0.18%, 0.19%, 0.2% or 0.21% by weight in the coating composition. Preferably aluminum exists at a value of 0.19% by weight in the coating composition.

The subject matter coating comprises zinc metal, and besides, it comprises determined amount of magnesium metal. The subject matter coating composition comprises magnesium at a value between 0.5% and 1%. Preferably, magnesium exists at a value which is equal to one of 0.6%, 0.7%, 0.8% or 0.9% by weight in the coating composition. Preferably, magnesium exists at a value of 0.83% by weight in the coating composition.

The subject matter coating composition comprises zinc, aluminum and magnesium components at determined weight proportions. The innovative characteristic of the present invention is that said components exist at different weight proportions when compared with coating compositions which have zinc-magnesium-aluminum composition known in the art. The present invention owners have conducted research and development activities on proportions of said components in the coating composition and they have obtained the coating composition which has the desired anti-corrosive effects. Accordingly, the present invention owners have provided a coating composition which comprises magnesium at a value between 0.5% and 1% by weight, aluminum at a value between 0.17% and 0.22% by weight and zinc for the remaining part and other elements in trace quantity. As seen, the present invention owners have detected that said components have high anti-corrosive effect for industrial products except iron, since said components exist in the coating composition with the mentioned proportions. The present invention owners have moreover detected that the coating composition, comprising magnesium component at a proportion between 0.5% and 1% by weight, aluminum component at a value between 0.17% and 0.22% by weight and zinc component for the remaining part, has high anti-corrosive activities also on the assembly, connection and cutting regions for iron-based industrial products. The subject matter coating composition provides formation of structures which can directly enter the crystal structure by adding the mentioned proportions of aluminum and magnesium components into zinc and which are placed between the tissues and by means of this, it changes the dissolving mechanism of the zinc-based galvanized coating composition and depending on this, it changes the formed products, and it provides the coating composition to have higher adhesion force and higher anti-corrosive effect when compared with iron-based industrial products, and besides, it increases the resistance values of the coating composition and provides longer lifetime coating compositions for iron-based products.

In one perspective, the present invention relates to a product comprising the subject matter coating composition.

The coating composition which exists in the subject matter product comprises magnesium at a value between 0.7% and 0.9% by weight, aluminum at a value between 0.18% and 0.2% by weight and zinc for the remaining part and other elements in trace quantity. In the most preferred application, the subject matter coating composition comprises magnesium at a value between 0.8% and 0.85% by weight, aluminum at a value between 0.185% and 0.195% by weight and zinc for the remaining part and other elements in trace quantity. The present invention owners have determined substantially narrow and selective value ranges when compared with Mg-AI-Zn galvanized coating compositions, known in the art, for selection of said components at the mentioned value ranges of the coating composition. In other words, it has been detected that the galvanized coating composition, comprising magnesium and aluminum components at value ranges mentioned by the research and development activities, has much higher salt fog edge and surface red rust hours when compared with conventional galvanized coating compositions known in the art. In the invention, as high salt fog edge cutting and surface red rust hour is being mentioned, values of 900 hours and above are mentioned. In the invention, ASTM B117 standards are applied for salt fog tests. While this value is 144 hours in coating thickness of 10 micrometers in traditional galvanized coating compositions, this value increases to between 984 and 1152 hours in coating thicknesses of 10 micrometers and 11 micrometers since the subject matter coating composition has components at the mentioned value ranges. Moreover, the values, where the subject matter coating composition and traditional galvanized coating composition are compared, are given in Table 1 .

In the invention, the coatings subjected to test as “traditional galvanized coating” describe the coatings comprising Al at a value between 0.15% and 0.3% and Zn for the remaining part.

Table 1. Comparison values of galvanized coating composition known in the art, and of galvanized coating composition which has the subject matter 1 ^st test 0.83% Mg+0.19%AI and 2 ^nd test 0.83% Mg+0.19% Al

When Table 1 is examined, it is seen that there are important differences in terms of both salt fog surface red rust hour and salt fog edge cutting red rust hours between the traditional galvanized coating compositions and the subject matter coating composition, which have the same coating thicknesses and same coating amounts. Moreover, it is seen by means of the results of the tests that the product which has the subject matter coating composition has higher hour/micrometer performance when compared with traditional coating compositions.

In Figure 1 , the views of salt fog test by means of raised hours between the traditional galvanized coating composition and 0.83% Mg+0.19% Al galvanized coating composition subjected to test are given. As it is apparent from the images, while red rust formation is observed in 1152 hours of the product salt fog test comprising the subject matter coating compositions, this value is begun to be observed in 144 hours in traditional coating compositions.

In Figure 2, the edge sectional views of salt fog test by means of raised hours between the traditional galvanized coating composition and 0.83% Mg+0.19% Al galvanized coating composition subjected to test under the same standard conditions are given. As seen in these tests, while red rust formation is observed in 1704 hours of the salt fog test of the subject matter coating compositions, this value is begun to be observed in 168 hours in traditional coating compositions. The subject matter coating composition is preferably used as coating material in galvanized coating processes particularly for iron-based industrial products. In the most preferred application, in pot applications, the subject matter coating composition is used as coating material in galvanized coating processes.

Moreover, another characteristic of the activity of the subject matter coating composition is that the subject matter coating composition shows higher anti-corrosive effects in the same coating thicknesses when compared with the galvanized coating compositions used in the same art.

The subject matter flat steel, coated with a galvanized coating composition which is resistant against red rust formations on surface and on edge cutting regions, is a product which is applicable to industry and which can be subjected to mass production.

The protection scope of the present invention is set forth in the annexed claims and cannot be restricted to the illustrative disclosures given above, under the detailed description. It is because a person skilled in the relevant art can obviously produce similar embodiments under the light of the foregoing disclosures, without departing from the main principles of the present invention.