Electrolysis: processes – compositions used therein – and methods – Electrolytic analysis or testing – For properties of solid material
Patent
1997-12-22
2000-03-07
Tung, T.
Electrolysis: processes, compositions used therein, and methods
Electrolytic analysis or testing
For properties of solid material
204404, 204434, 2057765, G01N 2726
Patent
active
060335548
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a corrosion resistance test process for a test material comprised of a metal blank and a coating film formed on the metal blank, and an electrolytic test machine used for the corrosion resistance test.
BACKGROUND ART
A cathode peel-off test process is conventionally known as a test process for examining an adhesion force of the coating film of such a test material (for example, see Japanese Patent Application Laid-open No.7-195612).
In this test process, a procedure is employed which involves immersing a test material having a damaged portion formed on the coating film to reach the metal blank, into an aqueous solution of NaCl serving as an electrolytic liquid, and allowing a DC current to flow between the metal blank serving as a cathode and an electrode provided in the aqueous solution of NaCl.
During supplying the electric current, OH ion produced by the electrolysis of water on the side of the metal blank as the cathode causes the adhesion force of the coating film to the metal blank to be decreased from a starting point provided by the damaged portion of the coating film, thereby promoting the peeling-off and blistering of the coating film. In this way, the cathode peel-off test process has an advantage that the superiority and inferiority of the adhesion force of the coating film can be simply determined. However, corrosion of the metal blank accompanying the peeling-off of the coating film cannot be predicted, and the cathode peel-off test process suffers from a problem that the overall estimation of the corrosion resistance cannot be carried out for the test material.
Therefore, a cycle corrosion test (CCT) is employed which is capable of simultaneously estimating the deterioration of the coating film and the corrosion of the metal blank.
However, the cycle corrosion test is accompanied by a problem that it requires a lot of test time and for this reason, a test result cannot be obtained early.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a corrosion resistance test process of the above-described type, which is capable of simultaneously estimating the peeling-off of the coating film and the corrosion of the metal blank, and in which the test time can be shortened.
To achieve the above object, according to the present invention, there is provided a corrosion resistance test process for a test material, comprising the steps of immersing, into an electrolytic liquid, a test material which is comprised of a metal blank and a coating film formed on the metal blank and which has a damaged portion extending to reach the metal blank, and allowing a DC current to flow between the metal blank and an electrode in an electrolytic liquid, while the polarity of the metal blank is alternately switched over from positive to negative polarity or vice versa.
In the above test process, when the polarity of the metal blank is negative, a coating film peeling-off step is carried out. On the other hand, when the polarity of the metal blank is positive, a metal blank corroding step, namely an anode oxidation step is carried out. By alternately repeating the coating film peeling-off and the anode oxidation in the above manner, the peeling-off of the coating film and the corrosion of the metal blank from the starting point provided by the damaged portion can be promoted, thereby performing an overall estimation of the corrosion within a short time.
The above test process is also applied to a test material which does not have a damaged portion as described above. In this case, a thinner portion of the coating film, a pin hole or the like serves as a starting point for the peeling-off of the coating film and the corrosion of the metal blank.
It is another object of the present invention to provide an electrolytic test machine which is suitable for carrying out the above-described corrosion resistance test process.
To achieve the above object, according to the present invention, there is provided an electrolytic test machine used
REFERENCES:
patent: 3223598 (1965-12-01), Jacky et al.
patent: 3660249 (1972-05-01), Townsend
patent: 3840439 (1974-10-01), Marsh
patent: 4294667 (1981-10-01), Yamamoto et al.
patent: 4425193 (1984-01-01), Taylor
patent: 5076906 (1991-12-01), DerMarderosian
Imanaka Tadashi
Kaneko Katsuyoshi
Takeuchi Toshihiro
Takikawa Kazunori
Honda Giken Kogyo Kabushiki Kaisha
Tung T.
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