JP5921888B2 - Corrosion measurement method and corrosion environment gauge - Google Patents

Description

  The present invention relates to a corrosion measurement method for measuring the corrosivity in a measurement environment and the corrosion state of a structure, and a corrosion environment gauge suitable for carrying out the method.

  So far, various methods for measuring the corrosiveness in the environment and the corrosion state of structures installed in the environment have been disclosed. For example, Patent Documents 1 and 2 disclose a method for determining a corrosion state or a deterioration state of a steel material from the brightness, saturation, and hue of the color of the outer surface of the steel material constituting the structure. Patent Document 3 discloses a plurality of types of sacrificial metal thin films that discolor due to deterioration factors in the atmosphere involved in corrosion of steel structures in order to grasp the progress of corrosion of the steel structures at an early stage. A method for evaluating the degree of corrosion of a steel structure from discoloration of a thin film using a corrosive environment sensor arranged on a corrosive and non-conductive substrate is disclosed. Further, Patent Document 4 discloses a method for evaluating the corrosiveness in the environment by changing the color of a metal thin film formed by changing the film thickness stepwise or continuously.

  Alternatively, Patent Document 5 discloses a method for measuring a corrosion rate using an AC impedance method. Patent Document 6 measures the electrical resistance value of a metal conductive member having a surface covered with an electrically insulating member and a surface exposed to the outside, and the electrical resistance value increases due to the progress of corrosion. A method for measuring the amount of corrosion of a structure is disclosed.

JP 2001-4525 A Japanese Patent Laid-Open No. 11-132962 JP-A-2005-121510 JP-A-10-90165 JP 2002-71616 A JP 2007-292747 A

  However, in the methods disclosed in Patent Documents 1 to 4, it is difficult to quantitatively evaluate the corrosivity in the environment and the corrosion state of the structure, using an index of color change. In addition, the methods disclosed in Patent Documents 5 and 6 require preparation of measuring instruments, wiring, and the like, and the corrosion state of the structure cannot be easily measured.

  The present invention has been made in view of the circumstances as described above, and the present inventors have quantitatively and easily measured the corrosivity in the environment and the corrosion state of the object to be measured, and The object was to provide a corrosive environmental gauge suitable for the implementation of the method.

  The corrosion measurement method of the present invention that has solved the above-described problems is a method of placing a metal plate having a portion where the thickness changes stepwise or continuously in a measurement environment, and retreating the predetermined portion of the metal plate after a predetermined time has elapsed. It is characterized by measuring the length.

  In the present invention, the predetermined location is the minimum thickness location of the metal plate, the metal plate is wedge-shaped, the entire inclined surface is concave, or the metal plate has a groove-shaped hole. Further, the holes of the metal plate are trapezoidal when the thickness direction is viewed from the side, have an inclined surface at a substantially uniform ratio, and the projection view in the thickness direction of the metal plate is circular. It is a preferred embodiment that the one surface is exposed while the metal plate is buried in the corrosion-resistant resin body.

  Further, the present invention includes a corrosive environment gauge characterized in that a metal plate whose thickness changes stepwise or continuously is buried in a corrosion-resistant resin body and one surface is exposed.

  In the corrosion environment gauge, the metal plate is wedge-shaped, the projection in the thickness direction of the metal plate is circular, the surface of the metal plate is blasted, and the corrosion-resistant resin body. It is a preferable embodiment that is a polyester resin body or an acrylic resin body, and that the corrosion-resistant resin body contains a conductive agent.

  In the corrosion measurement method of the present invention, a metal plate with a varying thickness is left in a measurement environment, and the receding length of a predetermined location (preferably, the minimum thickness location) is measured for the metal plate after a predetermined time has elapsed. Thus, the corrosivity in the environment and the corrosion state of the object to be measured are evaluated, and the corrosivity and the like can be measured quantitatively.

  Further, as described above, the corrosion measuring method of the present invention can be easily implemented because the corrosiveness in the environment and the corrosion state of the object to be measured are evaluated by the index of length.

It is the front view (a) and side view (b) of one embodiment of the metal plate used by this invention. It is a figure explaining the measuring method of the retreat length in the predetermined location when the projection figure (front view) of a plate | board thickness direction uses a circular metal plate. It is a figure explaining one embodiment of the corrosive environment gauge of this invention which has a wedge-shaped metal plate and the whole inclined surface has a recessed shape. The metal plate has a groove-like hole, and the hole of the metal plate is trapezoidal when viewed in the thickness direction from the side, and has the inclined surface at a substantially uniform ratio. It is a figure explaining one embodiment.

  The corrosion measurement method of the present invention is to place a metal plate having a portion where the thickness changes stepwise or continuously in a measurement environment, and measure the receding length of the predetermined portion of the metal plate after a predetermined time has elapsed. Features. Hereinafter, the corrosion measurement method of the present invention will be described in detail.

(Metal plate)
The metal plate used in the present invention has a portion where the thickness changes stepwise or continuously. The metal plate used in the present invention is only required to be retracted at a predetermined portion (preferably, a minimum thickness portion) of the metal plate due to thinning, and the portion where the thickness changes is provided in a part of the metal plate. Alternatively, the metal plate may be provided over the entire metal plate. However, in order to increase the retracted length of the predetermined portion in a predetermined time, the portion is preferably provided over the entire metal plate. In addition, when the location where thickness changes is provided in a part of metal plate, the said metal plate may have two or more said locations. In addition, the metal plate used in the present invention has a plurality of inclined surfaces having different thickness change rates (inclination angles) by providing a concave shape, for example, a U-shaped or V-shaped groove along the inclined surface. You may form (FIG. 3 mentioned later). With this configuration, the retreat length can be measured at an optimum location according to the measurement environment.

  Specific examples of the shape of the metal plate used in the present invention include, for example, a wedge shape as shown in FIG. 1, a metal plate (for example, a conical shape) whose projection in the thickness direction is circular, and a front surface. Examples include a rectangular shape (or a circular shape) having a circular arc on the side surface and the thickness continuously changing over the entire metal plate and the thickness decreasing toward at least one end of the metal plate. In addition, the front surface is rectangular (or circular) and the side surface is V-shaped, etc., and the thickness continuously changes over the entire metal plate, and the thickness decreases toward the approximate center of the metal plate. Examples include a shape in which the thickness changes stepwise over the entire metal plate and the thickness decreases toward at least one end of the metal plate, such as a rectangular shape (or a circular shape) and a stepped side surface. . By using a metal plate whose front surface (or projection in the plate thickness direction) is circular, the direction of the corrosive environment (the direction of the degree of corrosion deterioration) can be read from the direction of thinning. Alternatively, when a groove-like hole is formed in the metal plate, for example, when the thickness direction is viewed from the side, a hole having a trapezoidal shape is formed so as to have an inclined surface at a substantially uniform ratio, and the back surface of the metal plate is defined as an air exposure surface. In this case, an aspect in which the thickness of the metal plate decreases from a smaller direction toward a larger direction can be given.

  In the present invention, it is preferable to use a metal plate having a portion where the thickness continuously changes, and it is more preferable to use a wedge-shaped metal plate or a conical metal plate from the viewpoint of easy processing of the metal plate. Further, when the thickness direction is viewed from the side, it is more preferable to use a metal plate having a trapezoidal groove-like hole. With the metal plate having such a shape, the retreat of the minimum thickness portion accompanying the thinning of the metal plate continuously occurs, so that the measurement accuracy can be increased.

  The material of the metal plate used in the present invention is not particularly limited as long as the metal plate is thinned in a measurement environment including corrosion factors such as moisture, chloride ions, sulfide ions, nitrogen oxide ions, For example, a metal having a corrosion potential row on the low potential side can be given. Specifically, metals such as Mg, Al, Cd, Al-Mg alloys, Al-Mn-Mg alloys, Al-Zn alloys, Al-Mn alloys such as Al-Mn alloys, mechanical structural steels, tool steels, etc. Special steel or ordinary steel can be used.

  The corrosion measurement method of the present invention may be performed using a single type of metal plate composed of the above materials, or may be performed by combining two or more types of metal plates of different materials.

  The thickness of the metal plate used in the present invention is preferably set so that the backward movement at a predetermined position in a predetermined time can easily proceed. About specific thickness, it can design suitably with the material of a metal plate. For example, when using a steel plate, the minimum thickness portion of the metal plate is 0.05 mm or less (more preferably 0.03 mm or less), and the maximum thickness portion of the metal plate is 0.1 mm or more (more preferably 0.15 mm or more). ) Is preferred. If the maximum thickness portion of the metal plate is less than 0.1 mm, the metal plate may disappear completely in a short period from the start of measurement, and the method of the present invention may not be performed over a long period. In addition, although the upper limit of the thickness of the maximum thickness part of a metal plate is not specifically limited, For example, when installing a metal plate in a water path and implementing the method of this invention, a metal plate is water. It is preferable not to change the flow.

  The size of the metal plate used in the present invention is not particularly limited, and can be appropriately designed depending on the material of the metal plate. For example, when a steel plate having a rectangular front surface is used, the length in the direction (width direction) orthogonal to the length direction is 3 cm or more (more preferably 5 cm or more) when the steel plate is viewed from the front. Is preferred. If the length in the width direction is less than 3 cm, the corrosion area is small, and therefore, the variation in the retracted length at a predetermined location becomes large, and the corrosivity may not be measured accurately. In addition, corrosion progress from the width direction may occur, and the corrosion length may not be measured accurately.

(Corrosion measurement method)
In order to measure the corrosiveness in the measurement environment using the method of the present invention, for example, referring to FIG. That is, the metal plate according to the present invention is left for a predetermined time in an environment containing a predetermined amount of a predetermined corrosion factor (a metal plate whose thickness has been reduced after being left is indicated by a broken line). Next, an imaginary line orthogonal to the thickness direction is provided from an arbitrary position A of the metal plate to a predetermined position (for example, the minimum thickness position B) of the metal plate, and perpendicular lines are respectively dropped on the imaginary lines, and between the intersections. Find the distance 1. Subsequently, an intersection distance 2 between an intersection obtained by dropping a perpendicular line from the end of the metal plate before the measurement and an intersection obtained by dropping a perpendicular line from the location A to the virtual line on the extension line of the virtual line. The difference between the distances between the two intersections (inter-intersection distance 2−inter-intersection distance 1) is calculated to obtain the receding length of the minimum thickness portion, and a calibration curve for the predetermined environment is created from the receding length. . Thereafter, the receding length of the metal plate is obtained in a desired environment by the same method as described above, and the corrosivity in the environment is evaluated from the calibration curve.

  At that time, when there are a plurality of predetermined locations (for example, the minimum thickness location B) in the metal plate, one location may be arbitrarily selected. However, a location with a long receding length is selected to improve the measurement sensitivity. It is preferable to raise.

  When a metal plate (for example, a conical metal plate) having a circular projection in the plate thickness direction is used, for example, as shown in FIG. 2, the minimum thickness portion from the center (maximum thickness portion) is used. What is necessary is just to create the equivalent circle which makes the radius the average value of the length of (for example, 12 points), and calculate the amount of thinning.

  When the minimum thickness portion of the metal plate is in the metal plate, the distance 1 between the intersections is obtained by the same method as described above, and is located on the extension line of the imaginary line and from the portion having the smallest thickness before the measurement. The distance 2 between the intersections is obtained from the intersection obtained by dropping the perpendicular to the imaginary line and the intersection obtained by dropping the perpendicular from the location A to the imaginary line, and the difference between the intersections (distance between the intersections 2−distance between the intersections 1 ) May be calculated.

  The measurement of the corrosion state of the object to be measured (structure) according to the present invention is performed by installing the metal plate of the present invention on the object to be measured for a predetermined time and obtaining the receding length at a predetermined position by the same method as described above. do it. At this time, the material of the metal plate and the object to be measured may be the same or different, but it is preferable that the metal plate is made of the same material as the object to be measured because the corrosion state of the object to be measured can be directly measured. The object to be measured is not particularly limited, and examples thereof include steel structures such as steel towers, chimneys, and bridges.

  When a metal plate is placed on the object to be measured and the corrosion state of the object to be measured is measured, the metal plate is an insulating plate member (for example, a glass plate or a plate made of a corrosion-resistant resin, which will be described later). It is preferable to be placed on the structure. When the metal plate and the object to be measured are made of different materials, if the metal plate is placed directly on the object to be measured, the metal plate will be different from the object to be measured due to the difference in corrosion potential between the metal plate and the object to be measured. May be affected and corroded.

(Corrosion environment gauge)
The corrosion measurement method of the present invention can be suitably performed by using a corrosion environment gauge described below. Hereinafter, the corrosion environment gauge of the present invention will be described in detail.

  The corrosive environment gauge of the present invention is characterized in that a metal plate having a portion where the thickness changes stepwise or continuously is buried in a corrosion-resistant resin body while exposing one surface of the metal plate. To do. One embodiment of the corrosive environment gauge is shown in FIG.

  Alternatively, in the corrosion environment gauge of the present invention, the metal plate having a portion where the thickness changes stepwise or continuously has a groove-like hole, and the hole of the metal plate is seen from the side in the thickness direction. In this case, it is trapezoidal and is configured to have inclined surfaces at a substantially uniform rate. One embodiment of the corrosive environment gauge is shown in FIG.

  If the corrosion measurement method of the present invention is performed using the corrosion environment gauge shown in FIG. 3, only one surface of the metal plate 20 exposed from the corrosion-resistant resin body 10 is exposed to the measurement environment. Accordingly, the metal plate 20 is reduced in thickness in the thickness direction. As a result, if the position where the retraction length is obtained is set to the minimum thickness position, the retraction of the position occurs only from the end portion on the side where the thickness is small.

  For this reason, along the direction in which the minimum thickness portion recedes, the length scale of the metal plate starts from the vicinity of the end portion on the smaller thickness side of the metal plate 20 and the end point near the end portion on the larger thickness side. By providing it on the surface of the corrosion-resistant resin body 10 (for example, the front surface, side surface, and back surface of the corrosion-resistant resin body), it becomes possible to more easily evaluate the corrosiveness in the measurement environment.

  If the corrosion measurement method of the present invention is performed using the corrosion environment gauge shown in FIG. 4, only the back surface of the metal plate 30 is exposed to the measurement environment, so that the thinning progresses generally in the thickness direction of the metal plate 30. become. As a result, if the position where the retraction length is determined is set to the minimum thickness position, the retraction of the position occurs only from the groove end portion on the side where the thickness is small.

  For this reason, along the direction in which the minimum thickness portion recedes, the length scale of the metal plate starts from the vicinity of the groove end on the side where the thickness of the metal plate 30 is small, and the end near the end of the groove on the side where the thickness is large By providing it on the back surface of the metal plate 30, it becomes possible to more easily evaluate the corrosivity in the measurement environment.

  The type of the corrosion-resistant resin used in the corrosive environment gauge of the present invention is not particularly limited as long as it does not deteriorate in the usage environment. For example, acrylic resin, urethane resin, epoxy resin, polyester Resin and vinyl chloride resin. These resins may be used alone or in combination of two or more. When a transparent resin such as a polyester resin or an acrylic resin is used as the corrosion resistant resin, it is possible to read the calibration curve provided on the surface of the corrosion resistant resin body from the back surface of the corrosion resistant resin body. Further, a conductive filler may be added to the corrosion-resistant resin to increase the conductivity of the corrosion-resistant resin and minimize the difference in heat capacity from the object to be processed (structure) for measuring the corrosion state.

  The shape of the corrosive environment gauge of the present invention is not particularly limited, and may be rectangular or circular, but it is preferable that at least one side surface (preferably, all side surfaces) be tapered. With this configuration, even if the corrosive environment gauge of the present invention is installed in a puddle location or a water flow path, water easily collects in the corrosive environment gauge (on one surface of the metal plate).

  Moreover, when using the corrosion measuring method of this invention using the corrosion environment gauge of this invention, it is preferable to install so that one surface of a metal plate may follow a gravity direction as much as possible. According to this aspect, it is possible to prevent water from accumulating at the location where the metal plate has been thinned.

(Metal plate and corrosion environment gauge manufacturing method)
The manufacturing method of the metal plate used by this invention is not specifically limited, For example, the method of grind | polishing a metal plate with a grinder or etching and processing to a predetermined shape is mentioned. Furthermore, there is a method of processing while maintaining a certain inclination by general end mill processing.

  Further, the method for producing a corrosive environment gauge used in the present invention is not particularly limited. For example, a metal plate is placed on one side of the mold at the approximate center of the mold, and then the corrosion-resistant resin is formed. After pouring the heated melt from above, cool and cure, or when the above-mentioned corrosion-resistant resin is liquid at room temperature, cast the corrosion-resistant resin into the mold and then cure it with a curing agent. And manufacturing method.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

1. Production of Metal Plate Using a carbon tool steel material having a length of 50 mm, a width of 40 mm, and a thickness of 0.2 mm, the surface was mechanically polished to produce a wedge-shaped metal plate (FIG. 1). Note that a V-shaped groove having a maximum width of 40 mm and a maximum depth of 0.15 mm was formed on the wedge-shaped inclined surface (FIG. 3).

  Further, a carbon tool steel material having a length of 50 mm, a width of 50 mm, and a thickness of 0.2 mm was used, and the surface was mechanically polished to prepare a conical metal plate having a bottom diameter of 50 mm and a height of 0.2 mm.

  Furthermore, when a carbon tool steel material having a length of 70 mm, a width of 20 mm, and a thickness of 3 mm is used and the surface is processed with a drill having a diameter of 5 mm and the thickness direction is viewed from the side, a trapezoidal groove-like hole (substantially uniform as the bottom surface) A metal plate having an inclined surface at a certain ratio and a thickness of the metal plate in the hole portion from 0.05 mm to 0.20 mm was produced (FIG. 4).

2. Production of Corrosion Environment Gauge A wedge-shaped metal plate shown in FIG. 1 is placed in the center of the mold with the machine-polished side facing up, and then heated and melted polyester resin (Marumoto Struers, cold Penetration resin No. 105) was poured and cooled and cured. Thereafter, the polyester resin plate was processed into a predetermined shape to produce a corrosion environment gauge shown in FIG. Similarly, a corrosive environment gauge was produced in which a conical metal plate was buried in a polyester resin and the bottom surface was exposed. The metal plate shown in FIG. 4 was used as it was as a corrosive environment gauge with the back surface exposed to the atmosphere.

3. Preparation of calibration curve A scale of the length of the metal plate was provided along the longitudinal direction (reverse direction of the minimum thickness portion) of the metal plate on the front and back surfaces of the corrosion environment gauge shown in FIG. Similarly, a scale of the length of the metal plate was provided on the back surface of the corrosive environment gauge shown in FIG.

4). Corrosion Measurement After the corrosion environment gauge shown in FIG. 3 was left in the environment shown in Table 1 for 1 month, the recess length at the minimum thickness portion was measured. Further, the rate of thinning was calculated from the inclination rate (thickness / length) and the retreat length, and compared with the literature values. The results are shown in Table 1. In Table 1, “outside the cover” means an environment in which the corrosive environment gauge is exposed to rain, and “inside the cover” means an environment where no rain is applied.

  Table 1 shows that the measured value of the thinning rate is close to the literature value, so that the corrosive environment can be accurately performed by the measuring method of the present invention.

  Note that a wedge-shaped corrosive environment gauge in which a conical metal plate is buried in a polyester resin and one surface is exposed or a corrosive environment gauge made of a metal plate having a groove-shaped hole shown in FIG. It is considered that the same effect as the corrosion environment gauge shown in FIG.

10: Corrosion-resistant resin body 20, 30: Metal plate

Claims (10)

Expose a metal plate with a groove-like recess or hole whose depth changes stepwise or continuously on one surface to a measurement environment where only the back surface opposite to the one surface is a corrosive factor. The corrosion is characterized by being placed in the measurement environment and measuring the retracted length of the predetermined portion of the metal plate after a predetermined time has elapsed , wherein the predetermined portion is the minimum thickness portion of the metal plate Measuring method. The corrosion measurement method according to claim 1 , wherein the metal plate has a wedge shape, the one surface is inclined with respect to the back surface, and the inclined surface has the groove-shaped recess. The corrosion measurement method according to claim 1 , wherein the metal plate has a groove-shaped hole, and the hole has a trapezoidal shape when the thickness direction is viewed from the side. The corrosion measurement method according to any one of claims 1 to 3 , wherein the back surface is exposed while the metal plate is buried in a corrosion-resistant resin body. A metal plate having a groove-like recess or hole whose depth changes stepwise or continuously on one surface, and a back surface, which is a flat surface opposite to the one surface, is exposed to the measurement environment. A corrosive environment gauge characterized in that the back surface is exposed while being buried in a corrosion-resistant resin body. The corrosion environment gauge according to claim 5 , wherein the metal plate has a wedge shape, the one surface is inclined with respect to the back surface, and the inclined surface has the groove-shaped recess. The corrosion environment gauge according to claim 5 , wherein the metal plate has a groove-shaped hole, and the hole has a trapezoidal shape when the thickness direction is viewed from the side. The corrosion environment gauge according to any one of claims 5 to 7 , wherein the one surface of the metal plate is blasted. The corrosion environment gauge according to any one of claims 5 to 8 , wherein the corrosion-resistant resin body is a polyester resin body or an acrylic resin body. The corrosion environment gauge according to any one of claims 5 to 9 , wherein the corrosion-resistant resin body contains a conductive agent.

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