KR102466463B1 - Monitoring system for erosion corrosion and flow acceleration surface deterioration - Google Patents

Abstract

The present invention relates to being able to perform the evaluation of surface deterioration characteristics such as erosion, corrosion, and cavitation resistance of a material under flow conditions that simulate an actual flow environment, such as inside a pipe, in terms of weight reduction and electrochemical.
Erosion corrosion and flow acceleration surface deterioration monitoring system according to the present invention, a container for accommodating a fluid containing solid particles, a shaft disposed on one side of the container, a drive motor for rotationally driving the shaft, and one end of the shaft A specimen holder to be connected, a counter electrode spaced apart from the specimen holder and disposed in the container, a reference electrode spaced apart from the specimen holder and the counter electrode by a predetermined distance, and a specimen (working electrode) fixed to the specimen holder. It is characterized in that it comprises an electrochemical measuring device for measuring the electric potential.

Description

Erosion corrosion and flow acceleration surface deterioration monitoring system {MONITORING SYSTEM FOR EROSION CORROSION AND FLOW ACCELERATION SURFACE DETERIORATION}

The present invention relates to a system capable of monitoring surface deterioration caused by erosion, corrosion, and flow acceleration. In particular, surface deterioration characteristics such as resistance to erosion, corrosion, and cavitation of materials under flow conditions that simulate the actual flow environment such as inside a pipe It is about being able to accurately conduct an evaluation.

In general, since the inside of a pipe used in the petrochemical industry is exposed to environments such as severe erosion, corrosion, or cavitation, in order to select an appropriate pipe material, it is inevitably deteriorated in the flow acceleration environment such as erosion, corrosion, and cavitation characteristics. An evaluation of resistance is required.

As an evaluation method for surface deterioration due to erosion and corrosion, there is a method for measuring the electrochemical behavior accompanied by electron transfer based on the weight loss of the material and the anodic dissolution reaction of the surface (M → M ⁿ⁺ +ne ^- ) under flow acceleration conditions. . However, the conventional electrochemical behavior measurement method has a problem in that it is difficult to conduct an electrochemical experiment in a high-velocity flow environment because it reacts sensitively to the surface state of the material.

In addition, in the case of the conventional erosion/corrosion test method, which generates wear by spraying wear particles and liquid on the surface of the specimen from a high-pressure jet nozzle, it is suitable for simulating the high-speed fluid/particle collision situation and is mainly applied to jet turbine engines. Although it is widely used in the evaluation of materials, there is a problem that it is not suitable for the evaluation of erosion and corrosion damage occurring in the flow environment including slurry inside the pipe.

In addition, the RDE experimental apparatus, which is mainly used to exclude the effect of concentration polarization in electrochemical experiments in the research field such as catalysts, can be applied to the erosion and corrosion tests of metal materials in a flowing environment, but the specimen area exposed to the solution is Since it is extremely small, there is a problem in that it is not suitable for measurement of weight loss due to erosion and corrosion of bulk specimens and observation of surface cross-sections after testing.

Republic of Korea Patent Publication No. 10-2020-0041893

An object of the present invention is to provide a material surface deterioration monitoring system that can efficiently and accurately evaluate erosion and corrosion damage that is more accurate than the prior art and that occurs in an actual flow environment including slurry inside a pipe.

In order to solve the above problems, the present invention provides a container for accommodating a fluid containing solid particles, a shaft disposed on one side of the container, a drive motor for rotatingly driving the shaft, and a specimen holder connected to one end of the shaft; , a counter electrode spaced apart from the specimen holder and disposed in the container, a reference electrode spaced apart from the specimen holder and the counter electrode by a predetermined distance, and an electrochemical measuring device for measuring the potential of a specimen fixed to the specimen holder It provides a monitoring system for erosion corrosion and flow-accelerated surface deterioration comprising a.

In the monitoring system according to the present invention, the monitoring system may monitor erosion and corrosion generated while the specimen holder rotates in the fluid containing the solid particles by the driving motor through the electrochemical measuring device. .

In the monitoring system according to the present invention, the entire shaft or at least the surface of the shaft is made of a conductive material, and one side of the shaft is inserted and fastened and further includes a ring made of a conductive material, Two or more contact protrusions are formed on the inner surface so that an electrical connection between the ring and the shaft is maintained when the shaft is rotated, and one end of the ring is electrically connected to the electrochemical measuring device, and the specimen The potential of the specimen fixed to the holder may be measured.

In the monitoring system according to the present invention, the specimen holder includes an upper fixing part and a lower fixing part, and a fixing means for fastening the specimen between the upper fixing part and the lower fixing part by interposing the specimen, A fastening part to which one end of the shaft is fastened is formed on one side of the top part, and a connecting rod for electrically connecting the fastening part and a part in contact with the specimen is inserted in the upper fixing part.

In the monitoring system according to the present invention, the specimen holder includes a specimen support portion having an insertion space and an opening into which a specimen can be inserted, and fixing means for fixing the specimen inserted into the insertion space, the specimen support portion A fastening part to which one end of the shaft is fastened is formed on one side of the shaft, and a connecting rod for electrically connecting the fastening part and a portion in contact with the specimen is inserted in the specimen support part.

The monitoring system according to the present invention may further include a computer for recording and calculating the measurement result of the electrochemical measuring device.

In the monitoring system according to the present invention, the ring may be made of copper or a copper alloy.

In the monitoring system according to the present invention, the connecting rod may be made of copper or a copper alloy.

In the monitoring system according to the present invention, the connecting rod may be in electrical contact with the surface of the specimen through an O-ring.

In the monitoring system according to the present invention, the reference electrode may be installed inside or outside the container. However, it is more preferable to be installed outside the container under the high-speed rpm flow condition. In this case, it should be possible to exchange ions through a salt bridge or the like.

In the monitoring system according to the present invention, various electrochemical experiments are possible in a state where concentration polarization is completely controlled because the specimen holder on which the specimen is mounted rotates and agitates the solution. Accordingly, it is possible to not only secure accurate electrochemical data for evaluating the surface deterioration state of a material due to various erosion, corrosion, cavitation, etc., but also to measure the loss of erosion and to easily observe the surface cross-section of the specimen compared to the conventional method. .

In addition, the monitoring system according to the present invention can evaluate the electrochemical corrosion resistance of metallic materials that change in a flow environment even with a single experiment.

In addition, the monitoring system according to the present invention can efficiently and accurately evaluate the erosion and corrosion damage occurring in the flow environment including the slurry inside the actual pipe.

1 is a schematic diagram of a system for monitoring erosion corrosion and flow-accelerated surface deterioration according to an embodiment of the present invention.
2 is a perspective view and a plan view of a copper ring constituting the erosion corrosion and flow acceleration surface deterioration monitoring system according to an embodiment of the present invention.
3 is a perspective view before and after coupling of the specimen holder constituting the erosion corrosion and flow acceleration surface deterioration monitoring system according to an embodiment of the present invention.
4 shows the results of a weight loss experiment under corrosion and erosion/corrosion conditions using the erosion corrosion and flow acceleration surface deterioration monitoring system according to an embodiment of the present invention.
5 shows the electrochemical linear polarization test results in the erosion/corrosion test using the erosion/corrosion and flow-accelerated surface degradation monitoring system according to an embodiment of the present invention.
6 is a view showing a front part and a planar view shape when another type of specimen holder constituting the erosion corrosion and flow acceleration surface deterioration monitoring system according to an embodiment of the present invention is combined.

Hereinafter, the configuration and operation of the embodiment of the present invention will be described with reference to the accompanying drawings. In describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, when a part 'includes' a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

[Example 1]

1 is a schematic diagram of a erosion corrosion and flow acceleration surface deterioration monitoring system according to an embodiment of the present invention, and FIG. 2 is a copper ring constituting the erosion corrosion and flow acceleration surface deterioration monitoring system according to an embodiment of the present invention It is a perspective view and a plan view, and FIG. 3 is a perspective view before and after coupling of the specimen holder constituting the erosion corrosion and flow acceleration surface deterioration monitoring system according to an embodiment of the present invention.

1 to 3 , the erosion corrosion and flow acceleration surface deterioration monitoring system 100 according to Embodiment 1 of the present invention includes a container 110 for accommodating a fluid containing solid particles, and the container 110 ), a shaft 120 disposed on one side of the shaft 120 , a driving motor 130 for rotationally driving the shaft 120 , a specimen holder 140 connected to one end of the shaft 120 , and the specimen holder 140 . ) and an electrochemical measuring device ( 170) and a computer 180 for recording data of the electrochemical measuring device 170.

The container 110 includes a substantially cylindrical wall 111 , an upper cover 112 disposed on the upper portion of the wall, a lower cover 113 disposed below the wall, and the wall 111 interposed therebetween. and fastening means 114 for coupling the upper cover 112 and the lower cover 113 to each other.

In the upper cover 112 , a shaft hole 112a for inserting the shaft 120 , an electrode hole 112b for inserting the counter electrode 150 , and the fastening means 114 are fastened. Three fastening holes 112c for inserting the bar 114a are respectively formed. Three fastening holes 113a for inserting the fastening bars 114a constituting the fastening means 114 are also formed in the lower cover 113 . The fastening bar 114a is assembled through a fastening nut 114b.

On the other hand, the container 110 according to Example 1 of the present invention is not easily deformed or deteriorated by corrosion and/or abrasion environments in the container during corrosion/erosion experiments, and an appropriate weight is required so that it does not shake even when used at a high rpm do. Therefore, it is preferable that the wall 111, the upper cover 112, and the lower cover 113 are made of a material such as glass having an appropriate thickness. However, the material of the container 110 is not necessarily limited to glass and is not particularly limited as long as it can satisfy the above-mentioned requirements.

In addition, between the wall 111 and the upper cover 112 and between the wall 111 and the lower cover 112, an O-ring (not shown) made of a flexible material such as rubber to prevent leakage of fluid. time) to maintain liquid-tightness.

The shaft 120 is formed in a rod shape, and a threaded thread is formed at an end that is fastened to the specimen holder 140 . The shaft 120 is preferably made of a material having excellent electrical conductivity in order to also serve as a passage for electrons generated in an electrochemical reaction on the surface of the specimen. In addition, since it should not be corroded in a corrosive environment in the container 110 as well as strength and rigidity not to be bent when rotating at a high speed, it is preferably made of a material having excellent electrical conductivity and corrosion resistance, such as stainless steel.

As shown in FIG. 2 , a copper ring 190 is inserted into the shaft 120 to secure an electrical connection between the shaft 120 and the electrochemical measuring device 170 when the shaft 120 is rotated. has been installed

The copper ring 190 has a ring shape, and three protrusions 191 are formed to protrude at equal intervals so as to be in contact with the surface of the shaft 120 therein. A connection terminal 192 connected to a wiring for connecting to the electrochemical measuring device 170 is formed on the outer periphery of the copper ring 190 . The protrusion 191 functions to maintain electrical contact while the copper ring 190 does not rotate even when the shaft 120 rotates. As the copper ring 190, it is preferable to use copper or a copper alloy having good electrical conductivity, which has appropriate properties.

The copper ring 190 is preferably spaced apart by 0.2 mm or less so that the shaft 120 physically/electrically contacted with the working electrode (ie, the specimen S) can be contacted without turning while rotating.

On the other hand, although a copper ring is used in the embodiment of the present invention, for example, a bulk material of a material having excellent electrical conductivity, such as Pt, Au, Cu, Ag, or a material coated with the above materials may be used.

The driving motor 130 serves to rotate the shaft 120 connected to the specimen holder 140 at a constant rotation speed (rpm), and any type of motor may be used as long as it can rotate the shaft 120 . have.

As shown in FIG. 3 , the specimen holder 140 includes an upper fixing part 141 and a lower fixing part 142 formed in a 'T' shape, and between the upper fixing part and the lower fixing part. It is made including a specimen holder fastener 143 for fastening through the specimen. In addition, a copper bar 144 is inserted into the upper fixing part 141 .

On both sides of the 'T'-shaped protrusion of the upper fixing part 141 and the lower fixing part 142, the specimen holder fasteners 143 are respectively inserted and threaded into the inner peripheral surface for screwing insertion holes 141a. , 142a) are respectively formed. Since the upper fixing part 141 and the lower fixing part 142 are in physical and electrochemical contact with the specimen S, they are preferably made of a non-conductive material such as Teflon or plastic.

The specimen holder fastener 143 includes a fastening rod 143a having a threaded coupling portion processed on its outer circumferential surface, and a fastening nut 143b for fixing the fastening rod 143a after being inserted into the insertion holes 141a and 142a. ) is included.

The copper bar 144 has a rectangular bar-shaped cross-section, a fastening part having a larger cross-sectional area than the rod-shaped part is formed on the upper part, and the lower part is in contact with the specimen S. A screw hole 144a for inserting and fastening the shaft 120 is formed in the upper portion, so that the shaft 120 can be screwed. Through this shape, the inside of the specimen holder 140 is not worn and detachment can be prevented even during long-term driving. On the other hand, in the embodiment of the present invention, the copper bar 144 is made of a rectangular rod shape, but may also be formed of other polygons.

When the fastening rod 143a and the fastening nut 143b are fastened, one end of the copper bar 144 of the specimen holder 140 is in contact with the surface of the specimen S through an O-ring. and the other end is screwed with the shaft 120 . At this time, if the O-ring is too thick, the copper bar 144 and the specimen S do not come into contact with each other, and if the O-ring is too thin or the surface is uneven, crack corrosion occurs due to the penetration of the fluid, thereby reducing the reliability of the test results. Since it may be difficult to secure, it is preferable to use an O-ring with an appropriate thickness and a uniform surface.

As shown in FIG. 1 , the counter electrode 150 is inserted into the upper cover 112 so as to be spaced a predetermined distance from the fastening holder 140 and is fixed thereto.

The reference electrode 160 is an electrode for measuring a potential difference with a working electrode in a solution, and is fixedly disposed on one side of the wall 111 as shown in FIG. 1 . The reference electrode 160 may be installed in the container 110 , but considering that the environment in the container 110 is a flow acceleration environment, in the first embodiment of the present invention, the reference electrode 160 outside the container 110 . ) was installed.

The electrochemical measuring device 170 uses a three-electrode cell in order to minimize the error caused by the resistance when the resistance of the electrolyte is high or the flowing current is large. At this time, the three-electrode cell is composed of a working electrode (specimen holder), a reference electrode, and a counter electrode. In the three-electrode cell, current flows between the working electrode and the counter electrode, and the potential of the working electrode is controlled by a potential regulator with reference to the reference electrode. At this time, the potential difference between the working electrode and the reference electrode can be accurately measured regardless of the current value flowing by the electrode reaction. The electrochemical measuring device 170 may change the corrosion driving force of the metal by applying a potential or applying a current.

The measurement result of the electrochemical measuring device 170 is recorded through the data recording computer 180 .

The erosion corrosion and flow acceleration surface deterioration monitoring system 100 according to Embodiment 1 of the present invention operates as follows.

First, as shown in FIG. 3 , a plate-shaped specimen to be evaluated (S) is erected and sandwiched between the upper fixture 141 and the lower fixture 142 of the specimen holder 140, and then the specimen holder fastener 143 ) by using the upper fixture 141 and the lower fixture 142 to tighten the specimen (S) so that it is completely fixed. At this time, the copper bar 144 installed in the specimen S and the upper fixture 141 is in contact with the liquid-tight state through the O-ring.

As described above, the specimen holder 140 on which the specimen S is mounted is screwed to the end of the shaft 120 inserted into the upper cover 112 of the container 110 and fastened. And after covering the upper cover 112 to the container 110 in which the mixed solution of the fluid and the solid particles is injected, it is assembled with the lower cover 113 through the fastening bar 114a and the fastening nut 114b.

The drive motor 130 is operated to rotate the specimen S at high speed to collide with the fluid and solid particles, thereby causing corrosion and erosion in the specimen S.

Corrosion and erosion occurring in this process are performed by an electrochemical measuring device ( 170) is measured by the three-electrode cell of the working electrode (ie, the specimen S).

The monitoring device 100 according to Example 1 is exposed to the solution over the entire surface of the specimen S, and the specimen holder 140 rotates and stirs the solution, so that the concentration polarization is controlled, and electrochemical Behavior evaluation becomes possible.

In addition, it is possible to evaluate the electrochemical corrosion resistance of metal materials that change in a flow environment with one experiment, and after the evaluation is completed, it is easy to measure weight loss due to damage such as erosion, corrosion, and cavitation. In particular, the monitoring device 100 according to Example 1 has a structure suitable for weight loss measurement experiments as a measure for surface deterioration in erosion, corrosion, cavitation, and flow acceleration environments.

4 shows the results of a weight loss experiment under corrosion and erosion-corrosion conditions using the erosion corrosion and flow acceleration surface deterioration monitoring system according to an embodiment of the present invention.

The weight loss experiment was performed under the following conditions.

- Specimen: carbon steel

- Polishing: #800 or less

- Solution: 3.5% NaCl

- Immersion period: 1 day

- Rotation speed: 1055rpm

-Solid particles: 5% by weight added to the SiO ₂ particle solution with an average particle size of 250 μm

The graph of FIG. 4 is a value obtained by the following [Equation 1].

[Equation 1]

Weight loss (g/ ) = (weight before experiment (g) - weight after experiment (g))/specimen surface area ( )

From the results of FIG. 4 , it can be seen that the weight loss in the environment where erosion and corrosion occurs under flow conditions is significantly higher than the weight loss of the pure immersion type corrosion test.

5 shows the results of electrochemical linear polarization experiments in erosion-corrosion experiments using the erosion corrosion and flow-accelerated surface degradation monitoring system according to an embodiment of the present invention.

The flow acceleration conditions of FIG. 5 were the same as those of the weight loss experiment, and the applied potential was ±20mV vs. It is an open circuit potential, and the potential rising rate was set to 0.5 mV/s.

As can be seen in FIG. 5 , through the monitoring system according to Example 1, it was possible to stably acquire electrochemical polarization experimental data even during high-speed rotation of 1055 rpm.

[Example 2]

Since the monitoring system 200 according to the second embodiment of the present invention differs only in the structure of the specimen holder from the monitoring system 100 according to the first embodiment, a description of other components will be omitted. In addition, the same structure as Example 1 is demonstrated using the same reference numerals.

6 shows the front part and the plan view shape when the specimen holder 240 constituting the monitoring system 200 according to the second embodiment of the present invention is coupled.

6, the specimen holder 240 according to the second embodiment includes a 'T'-shaped specimen holder 241, a substantially rectangular ring 242 inserted into the specimen holder, and the specimen holder 241. It includes a specimen fixture 243 that prevents the mounted specimen S from being separated during the rotation process of the specimen holder 240 . A copper bar 244 having the same shape as that of Example 1 is inserted into the pillar portion of the 'T'-shaped specimen holder 241 .

The 'T'-shaped specimen holder 241 is disposed so that the protruding portions on both sides are located below, and the protruding portion has an opening 241a corresponding to the size of the specimen S so that the specimen S can be inserted. is formed. In addition, a stepped portion 241b is formed inside the opening 241a to support the inserted specimen S. In addition, a plurality of fastening holes 241c for fastening with the specimen fixture 243 are formed at edges of both protrusions of the specimen holder 241 .

The specimen fixture 243 has a substantially rectangular shape and has an opening 243a smaller than the size of the specimen S, and a plurality of fastening holes 243b for coupling to the specimen holder 241 are formed on the outer periphery. has been The specimen fixture 243 is coupled to the specimen holder 241 through screw coupling by a bolt 243c.

As shown in FIGS. 6B and 6C , the copper bar 244 has a rectangular bar-shaped cross section and a fastening part having a larger cross-sectional area than the lower bar-shaped part 244b, as in the first embodiment. (244a) is formed, the lower part is in contact with the specimen (S). A screw hole 244c for inserting and fastening the shaft 120 is formed in the fastening part 244a, so that the shaft 120 can be screwed.

The monitoring system 200 according to the second embodiment of the present invention operates through the following process.

In the specimen holder 240 according to the second embodiment of the present invention, the ring 242 is first inserted into the opening 241a to be supported by the step portion 241b. Next, after inserting the specimen S into the opening 241a, it is fixed using a specimen fixture 243 . Subsequent procedures are performed in the same manner as in Example 1.

100, 200: monitoring device
110: courage
120: axis
130: drive motor
140, 240: specimen holder
150: counter electrode
160: reference electrode
170: electrochemical measuring device
180: reference electrode container
190: copper ring

Claims (10)

A container containing a fluid containing solid particles, and
a shaft disposed on one side of the container;
a driving motor for rotating the shaft;
a specimen holder connected to one end of the shaft;
a counter electrode spaced apart from the specimen holder and disposed in the container;
a reference electrode disposed to be spaced apart from the specimen holder and the counter electrode by a predetermined distance;
An electrochemical measuring device for measuring the potential of a specimen (working electrode) fixed to the specimen holder,
the entire shaft or at least the surface of the shaft is made of a conductive material,
One side of the shaft is inserted and fastened further comprising a ring (ring) made of a conductive material,
Two or more contact protrusions are formed on the inner surface of the ring, so that the electrical connection between the ring and the shaft is maintained when the shaft is rotated,
One end of the ring is electrically connected to the electrochemical measuring device, and the potential of the specimen fixed to the specimen holder is measured. The method of claim 1,
The monitoring system, erosion corrosion and flow acceleration surface, characterized in that monitoring the erosion and corrosion occurring while the specimen holder rotates in the fluid containing the solid particles by the driving motor through the electrochemical measuring device Deterioration monitoring system. delete The method of claim 1,
The specimen holder includes an upper fixing part and a lower fixing part, and fixing means for fastening the specimen between the upper fixing part and the lower fixing part,
A fastening part to which one end of the shaft is fastened is formed on one side of the upper fixing part,
The erosion corrosion and flow acceleration surface deterioration monitoring system, characterized in that a connecting rod for electrically connecting the fastening portion and the portion in contact with the specimen is inserted in the upper fixing portion. The method of claim 1,
The specimen holder includes a specimen support having an insertion space and an opening into which a specimen can be inserted;
and fixing means for fixing the specimen inserted into the insertion space,
A fastening part to which one end of the shaft is fastened is formed on one side of the specimen support part,
Corrosion corrosion and flow acceleration surface deterioration monitoring system, characterized in that a connecting rod for electrically connecting the coupling portion and the portion in contact with the specimen is inserted in the specimen support portion. The method of claim 1,
The monitoring system is characterized in that it further comprises a computer for recording and calculating the measurement result of the electrochemical measuring device, erosion corrosion and flow acceleration surface deterioration monitoring system. The method of claim 1,
The ring (ring) is characterized in that made of copper or copper alloy, erosion corrosion and flow acceleration surface deterioration monitoring system. 6. The method according to claim 4 or 5,
The connection rod is characterized in that made of copper or copper alloy, erosion corrosion and flow acceleration surface deterioration monitoring system. 5. The method of claim 4,
The connection rod is in electrical contact with the surface of the specimen via an O-ring, erosion corrosion and flow acceleration surface deterioration monitoring system. The method of claim 1,
The reference electrode is characterized in that the ion exchange is installed inside or outside the vessel, erosion corrosion and flow acceleration surface deterioration monitoring system.

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