WO2006080542A1

WO2006080542A1 - Method of estimating corrosion resistance of metal or coated metal plate

Info

Publication number: WO2006080542A1
Application number: PCT/JP2006/301604
Authority: WO
Inventors: Daisuke Mizuno; Sakae Fujita; Hiroshi Kajiyama; Chiaki Kato
Original assignee: Jfe Steel Corporation
Priority date: 2005-01-26
Filing date: 2006-01-25
Publication date: 2006-08-03

Abstract

A method of estimating the corrosion resistance longevity of metal or coating layer used in corrosive environment. There is provided a method comprising the first step of determining the corrosion rate or corrosion resistance duration in multiple corrosion test environments; the second step of during the first step, determining the corrosion rate ratio in actual environment with respect to the actual environment and the multiple corrosion test environments; the third step of determining the corrosion rate ratio or corrosion resistance duration ratio relative to reference metal; and the fourth step of determining a correlation of the corrosion rate ratio or corrosion resistance duration ratio obtained in the second step and third step and from data of the correlation, determining the corrosion rate ratio between reference metal and other metals in actual environment.

Description

Description Method for predicting corrosion resistance of metals and coated metal sheets

The present invention relates to a corrosion resistance prediction method for predicting the life of metals and coated metal sheets used in corrosive environments. Background art

In recent years, there has been a social demand for extending the life of products such as automobiles, buildings, and home appliances and minimizing the life cycle cost. Durability equivalent to the required life as a structure is also required for the materials used for them. Of the durability of the materials used in the above structures, the corrosion resistance is generally evaluated by various corrosion promotion tests and exposure tests.

However, the actual useful life of these tests could not be determined because of the vague correlation with the actual usage environment. There is a need to predict the corrosion resistance life of materials in actual use environments and structures, or to design materials that satisfy the required corrosion resistance life without excess or deficiency.

Disclosure of the invention

Determining the corrosion resistance life from the amount of corrosion of a test piece by exposing the test piece to an environment close to the actual environment, it is decades when targeting materials used in structures such as automobiles and buildings. This requires a long test period. In addition, even if past exposure data exists, there is no simple correlation between the specimen and the complex structure of the actual structure. In conventional exposure tests, the corrosion resistance life of the actual structure is predicted. There was a problem that it was difficult to do. In addition, the corrosion life of materials is estimated by investigating the actual state of corrosion of actual structures that have been used for a long time. However, not only does it take a long time to corrode a real structure, but there is a problem that the time and cost required for the survey become enormous.

On the other hand, in order to evaluate the corrosion resistance of materials, various corrosion acceleration test methods have been standardized or new test methods have been proposed, but not only the actual environment and the corrosion mechanism are different, but also the correlation is ambiguous. Yes, there is a drawback that the order of corrosion resistance between materials is reversed in terrible materials.

The present invention has been made to solve the above-described problems, and predicts the corrosion resistance life of a material in a real environment or structure. The material predicted by the corrosion resistance prediction is The purpose is to provide embedded products. 'The gist of the present invention is as follows.

1. The first step of determining the corrosion rate or corrosion resistance time in multiple corrosion test environments for two metals A and B with known corrosion rates in the real environment and the metal C with unknown corrosion rates in the real environment. ,

A second step of determining the corrosion rate ratio of the metal B to the reference metal for the actual environment and the plurality of corrosion test environments, using the metal A as a reference metal;

For the metal C, a third step for obtaining a corrosion rate ratio or corrosion time ratio with respect to a reference metal by obtaining a corrosion rate or corrosion resistance time in the plurality of corrosion test environments from the result of the first step;

The correlation between the corrosion rate ratio of metal B with respect to the reference metal obtained in the second step and the corrosion rate ratio or corrosion resistance ratio of metal C with respect to the reference metal obtained in the third step is obtained, and this correlation is obtained. From the relationship, the corrosion rate ratio of metal C with respect to the reference metal in the actual environment or the corrosion resistance ratio can be calculated to determine the corrosion rate of metal C in the actual environment Or a fourth step to predict the corrosion resistance time,

A method for predicting corrosion resistance of a metal, characterized by comprising:

2. The method for predicting corrosion resistance of a metal according to item 1, wherein metal A as a reference metal is steel, metal B is zinc, and metal C is a zinc-containing alloy.

3. The reference metal, metal A, is steel, metal B is zinc or zinc plating, metal C is zinc-containing alloy or zinc-containing alloy plating including surface treatment layer,

The corrosion rate or corrosion resistance time of the metal C required in the first step is the average corrosion rate or total corrosion resistance time between the surface treatment layer and the zinc-containing alloy or zinc-containing alloy plating. A method for predicting the corrosion resistance of metals.

4. The method for predicting corrosion resistance of a metal according to item 1, wherein metal A as a reference metal is steel, metal B is zinc, and metal C is a surface treatment layer.

5. The method for predicting corrosion resistance of a metal according to item 3 or 4, wherein the surface treatment layer is one or more selected from a coating film, an organic film, an inorganic film, an organic-inorganic composite film, and a diffusion layer.

6. Using the corrosion rate or corrosion resistance of metal C obtained by the method for predicting corrosion resistance of metal according to any one of items 1 to 5, metal A is coated with metal C according to the following equation. A method for predicting the corrosion resistance of a coated metal sheet, characterized in that the corrosion resistance life of the coated metal sheet is obtained.

Corrosion resistance = (Coating layer (metal C) thickness Metal C corrosion rate) + (Under metal (metal A) thickness No metal A corrosion rate)

Corrosion resistance time of coating layer = (thickness of coating layer (metal C) Corrosion rate of metal C) 7. Setting of the corrosion rate or corrosion resistance of metal C obtained by the method for predicting corrosion resistance of metal according to any one of items 1 to 5, and setting of a coated metal plate in which metal A is coated with metal C A method for selecting a covered metal plate, wherein the thickness of the coating layer (metal C) is determined by the following equation using the measured corrosion resistance life and the thickness of the base metal (metal A).

Corrosion resistance = (Coating layer (metal C) thickness Z Metal C corrosion rate) + (Under metal (metal A) thickness No metal A corrosion rate)

Corrosion resistance time of coating layer = (Coating layer (metal) thickness Metal C corrosion rate)

8. Setting of the corrosion rate or corrosion resistance of metal C obtained by the method for predicting corrosion resistance of metal according to any one of items 1 to 5, and setting of a coated metal plate in which metal A is coated with metal C A method for selecting a coated metal plate, wherein the thickness of the base metal (metal A) is determined by the following formula using the measured corrosion resistance and the thickness of the base metal (metal C).

Corrosion life = (Coating layer (metal C) thickness Metal C corrosion rate) + (Under metal (metal A) thickness / Metal A corrosion rate)

Corrosion resistance time of coating layer = (thickness of coating layer (metal C) Corrosion rate of metal C)

9. The method for selecting a coated metal sheet according to item 7 or 8, wherein the coated metal sheet is used as a member of an automobile, a building material, or a home appliance.

1 0. Item 7 or 8 used as an inner / outer plate, frame, billet, member, reinforcement member such as reinforcement or beam, case, exhaust system part where the coated metal plate is used in automobiles with or without painting. The method for selecting a coated metal plate according to the item.

1 1. Corrosion rate or corrosion time of metal C obtained by the method for predicting corrosion resistance of metal according to any one of items 1 to 5, and metal A is not coated with metal C. The thickness of the coating layer (metal C) is determined by the following equation using the set corrosion resistance life of the coated metal plate and the thickness of the base metal (metal A). .

Corrosion life = (Coating layer (metal C) thickness Metal C corrosion rate) + (Under metal (metal A) thickness Z Metal A corrosion rate)

Corrosion resistance time of coating layer == (thickness of coating layer (metal C) Corrosion rate of metal C)

1 2. A member of an automobile, building material, or household electrical appliance that uses the coated metal sheet described in item 1 above.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart showing a process for predicting a corrosion resistance life of a metal and a coating layer, a design method from the metal and the coating layer and structure, and a manufacturing method thereof.

Figure 2 is an illustration of the metal structure for determining the corrosion rate.

Figure 3 is an illustration of the definition of corrosion rate in the corrosion test.

FIG. 4 is a characteristic diagram obtained by the embodiment (S T 2) in the present invention. Fig. 5 is an explanatory diagram of the relationship between the corrosion resistance life of the surface-treated metal and the thickness and corrosion rate of the coating layer and the underlying metal.

Figure 6 shows the relationship between the corrosion rate ratio of steel and the other two metals with respect to the corrosion rate ratio of steel and zinc obtained in the embodiment (ST 2) of the present invention. It is the figure which showed the comparison of the result of extrapolating to the corrosion rate of and the corrosion rate ratio in a real environment. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a flowchart of the corrosion resistance life prediction method for a metal and a coating layer according to an embodiment of the present invention, the design method for the metal, the coating layer and the structure, and the process of the manufacturing method. .

(ST 1): Product conditions are presented first. Product conditions include corrosive environment (use area, structure, part, etc.) and material conditions (corrosion amount, depth of corroded holes, coating blister width, thickness and type of underlying metal and coating layer, etc.).

(ST2): This is the process of predicting the corrosion resistance life of a metal whose corrosion rate in the actual environment is unknown, and can be composed of the following (ST 2-1) to (ST2-4) forces.

Here, as shown in Fig. 2, the metal that predicts the corrosion-resistant life or calculates the corrosion rate for prediction is as follows: (a) a single metal as a base, (b) a coating film, an organic film, A surface treatment layer selected from an inorganic coating, an organic-inorganic composite coating, a diffusion layer, a coating layer having a single layer composed of plating, or (c) a base metal having the above-mentioned multilayer coating layer is there. Including those with non-metallic components in the coating layer, (b) and (c) are collectively referred to as “coated metal plate”.

In Fig. 2 (a), al is a metal, in Fig. 2 (b), bl is a single surface treatment layer or coating layer, b2 is a base metal, and in Fig. 2 (c), cl, c2, c3 is a multilayer surface treatment layer or coating layer, and c4 is a base metal.

(ST2-1): This is a process to prepare data for life prediction. Two types of metals with known corrosion rates in the real environment (hereinafter referred to as metals A and B) and corrosion rates in the real environment Conduct multiple corrosion tests on the unknown metal (hereinafter referred to as Metal C), and determine the corrosion rate or corrosion resistance time for each. For example, as shown in Fig. 3, the corrosion rate is a value obtained by conducting a corrosion test for a certain period and converting the obtained corrosion amount into a corrosion amount for a unit period. The corrosion resistance time is the time required to reach the set amount of corrosion. Metal C may contain non-metallic components as described above. Metal C is a representative of multiple types of metals and need not be a single type. -

(ST2-2): Of the metals that have undergone the above corrosion tests, they have been used in products For the two types of metals A and B with known corrosion rates in the actual environment, use metal A as the reference metal, and calculate the corrosion rate ratio of metal B to this for the actual environment and multiple corrosion test environments.

(ST2-3): Corrosion rate for the reference metal (S, T2-2) in multiple corrosion test environments for metal C, whose corrosion rate in the actual environment is unknown due to reasons such as short development. Ratio or corrosion time ratio.

(ST2-4): Correlation between the corrosion rate ratio or corrosion resistance time ratio obtained in (ST2-2) above and the corrosion rate ratio or corrosion resistance ratio ratio obtained in (ST2-3) is obtained. Predict the corrosion rate ratio or corrosion time ratio of metal C to the reference metal in the environment. For example, by extrapolating the correlation regression curve obtained from the results of the corrosion test to the actual environment, the corrosion rate ratio or anti-corrosion time ratio of metal C to the reference metal in the actual environment is obtained, and the obtained corrosion Predict corrosion life from speed or corrosion time ratio.

For example, as shown in Fig. 4, the corrosion rate ratio of metal B, which has a known corrosion rate in the actual environment, to the reference metal is plotted on the horizontal axis for each corrosion test, and a vertical line is drawn at each plot position. Next, when the corrosion rate ratio of metal C, whose corrosion rate is unknown in the actual environment, is plotted on a vertical line for each corrosion test, a curve like the white circle in Fig. 4 is drawn, as shown by the arrow. The value of the corrosion rate ratio in the actual environment (indicated by black circles) can be estimated.

When the metal whose corrosion rate is predicted is the coating layer, the relationship between the corrosion rate of the surface-treated metal and the corrosion resistance life can be shown as in Fig. 5. That is, the total corrosion period is the sum of the corrosion period of the coating layer and the corrosion period of the base metal, and the following formula: 'corrosion resistance life = (corrosion allowable thickness of coating layer Z corrosion rate of metal C) + ( Corrosion allowable thickness of base metal / corrosion rate of base metal)

Can be used to determine the corrosion resistance life. The first term on the right side of this equation is the corrosion resistance time of the coating layer. (ST 3): Determine whether the corrosion life of the material obtained by the above processing (ST 2-1) or (ST 2-4) satisfies the required service life, and use it in products. Select the material to be used.

The material may be designed to meet the required service life and selected as a structural member for the product. For example, in the relational expression between the corrosion rate of the coated metal plate and the corrosion resistance life, when the corrosion resistance life and the allowable corrosion thickness of the base metal are known, the allowable corrosion thickness of the coating layer is set as follows. When the allowable corrosion thickness is known, the thickness of the metal and coating layer and the thickness of the underlying metal can be determined by determining the allowable corrosion thickness of the underlying metal.

When there is no metal C satisfying the service life, a new design is made using the life prediction method of the present invention. .

【Example】

(Example 1)

Table 1 shows the results of determining the corrosion rates in three types of conventional corrosion test machines and real environments for four types of metals. Here, the base metal plate (symbol F e, the same applies below) and zinc plating (Z n) have a track record in the actual environment, and a zinc-containing alloy with a Z n alloy (ZA) coating and organic coating. Metsuki (OZA) has not been used in actual environments so far, and the corrosion rate was unknown. Table 1 Corrosion test 1 Corrosion test 2 Corrosion test 3 Actual environment Life μ m / cy β m./cy m / day m

F e 20 300 50 150 ―

Z n 4 10 0.9 2.0 ―

-ZA 1 7 0.9 ― X

OZA 0.3 3.5 0.55 X

In the three types of corrosion tests and in the actual environment, the change in the corrosion rate of each metal is not constant.From the relationship with the corrosion rate of metals that have been used in the past, such as various corrosion tests alone, or steel and zinc plating, zinc For metals with unknown corrosion rates in the real environment, such as alloys and zinc-containing alloys with organic coatings, the corrosion rate and corrosion resistance life could not be predicted. (Life judgment X).

(Example 2)

Table 2 summarizes the results obtained in Example 1 by the processing of the embodiment (ST2-2) in the present invention. Corrosion rate ratios with the other three metals were determined based on steel among the four metals. ,

Table 2 Corrosion test Corrosion test 2 Corrosion test 3 Actual judgment Judgment 1

F e / Z n 5 30 56 75 ―

F e / ZA 20 43 56 [65] ◎

F eZOZA 67 86 83 [88〗 ◎

With regard to this corrosion rate ratio, the corrosion rate ratio between steel with known corrosion rate in the actual environment and zinc galvanized Zn is plotted on the horizontal axis, and the corrosion rate ratio of other metals is plotted using the method described in Fig. 4, Figure 6 plots the corrosion rate ratio in the actual environment and predicts the corrosion rate in the actual environment. Table 2 shows the predicted values (indicated by []).

The prediction results correspond well with the values of the corrosion rate ratios for zinc alloys and zinc-containing alloys with organic coatings measured in the actual environment,

(Decision A), the results of the corrosion test showed that the corrosion rate of zinc-containing alloy plating with a zinc alloy and an organic film in an actual environment can be predicted.

Industrial applicability ''

According to the method for predicting corrosion resistance of the present invention, a metal whose corrosion resistance is unknown in the actual environment / actual structure (plating film, based on the relative corrosion rate ratio of two or more metals that have been used in the actual structure for a long time) It is possible to accurately estimate the corrosion rate of unknown metals in the actual environment and actual structure through a short-term corrosion acceleration test, and to calculate the corrosion resistance life. In addition, it is possible to design the life of a real structure and contribute to the recently demanded life cycle cost life technology.

Claims

The scope of the claims

The correlation between the corrosion rate ratio of metal B with respect to the reference metal obtained in the second step and the corrosion rate ratio or corrosion resistance ratio of metal C with respect to the reference metal obtained in the third step is obtained, and this correlation is obtained. A fourth step of predicting the corrosion rate or corrosion resistance time of metal C in the actual environment by determining the corrosion rate ratio or corrosion resistance ratio of metal C to the reference metal in the actual environment from the relationship;

2. The method for predicting corrosion resistance of a metal according to claim 1, wherein metal A as a reference metal is steel, metal B is zinc, and metal C is a zinc-containing alloy.

The corrosion rate or corrosion resistance time of the metal C required in the first step is an average corrosion rate or total corrosion resistance time of the surface treatment layer and zinc-containing alloy or zinc-containing alloy plating. The method for predicting corrosion resistance of a metal according to Item.

4. The reference metal, metal A, is steel, metal B is zinc, and metal C is the surface treatment layer. The method for predicting corrosion resistance of a metal according to claim 1.

5. The method for predicting corrosion resistance of a metal according to claim 3 or 4, wherein the surface treatment layer is one or more selected from a coating film, an organic film, an inorganic film, an organic-inorganic composite film, and a diffusion layer.

6. By using the corrosion rate or corrosion resistance of metal C obtained by the method for predicting corrosion resistance of metal according to any one of claims 1 to 5, metal A is metal A method for predicting the corrosion resistance of a coated metal sheet, characterized in that the corrosion resistance life of the coated metal sheet coated with C is obtained.

Corrosion resistance = (Coating layer (Metal C) thickness / Metal C corrosion rate) + (Under metal (Metal A) thickness / Metal A corrosion rate)

Corrosion resistance time of coating layer = (thickness of coating layer (metal C) / corrosion rate of metal C)

7. Corrosion rate or corrosion time of metal C obtained by the method for predicting corrosion resistance of metal according to any one of claims 1 to 5, and a coated metal obtained by coating metal A with metal C A method for selecting a coated metal plate, wherein the thickness of the coating layer (metal C) is determined by the following equation using the set corrosion resistance life of the plate and the thickness of the base metal (metal A).

Corrosion resistance = (Coating layer (Metal C) thickness / Metal C corrosion rate) + (Under metal (Metal A) thickness No Metal A corrosion rate)

Corrosion resistance time of coating layer = (thickness of coating layer (metal C) Z corrosion rate of metal C)

8. Corrosion rate or corrosion time of metal C obtained by the method for predicting corrosion resistance of metal according to any one of claims 1 to 5, and a coated metal formed by coating metal A with metal C Using the set corrosion resistance life of the plate and the thickness of the coating layer (metal C), the thickness of the base metal (metal A) is determined by the following formula: How to select the coated metal plate.

9. The method for selecting a coated metal sheet according to claim 7 or 8, wherein the coated metal sheet is used as a member of an automobile, a building material, or a household electrical appliance.

1 0. Claim 7 or claim 7 where the coated metal plate is used as an inner / outer plate, frame, pillar, member, reinforcement member such as reinforcement or beam, case, exhaust system part used for coated or unpainted automobiles Method for selecting coated metal sheet according to item 8.

1 1. Corrosion rate or corrosion time of metal C determined by the method for predicting corrosion resistance of metal according to any one of claims 1 to 5, and metal A is covered with metal C. The coated metal plate is characterized in that the thickness of the coating layer (metal C) is determined by the following formula using the set corrosion resistance life of the coated metal plate and the thickness of the base metal (metal A).

Corrosion resistance = (Coating layer (metal C) thickness / Metal C corrosion rate) + (Under metal (Metal A) thickness Z Metal A corrosion rate).

1 2. A member of an automobile, a building material, or a home appliance using the coated metal sheet according to claim 11.