JP3777934B2 - Method and apparatus for measuring corrosion in non-aqueous organic liquids - Google Patents

Description

【００１８】
ここで、ΔＥは電位の変化量
ΔＩは電流の変化量
Ｒは腐食の電気化学的抵抗
をそれぞれ示すものである。
【００１９】
【数２】
腐食率＝Ｋ×Ｒ
【００２０】
ここでＫは金属材質と流体性状により決まる係数であり、金属試験片の腐食減量より逆算して求めることもできるし、また測定で求めることができる。
【００２１】
（腐食測定装置）
本発明の腐食測定装置とは、腐食測定対象の金属表面と同じ材質を有する複数の電極、該電極の金属表面に酸化物を形成させる手段、該酸化物を形成させてなる電極を非水系有機液中における腐食条件下に曝らす手段、該電極間の電気化学的電流ノイズ及び電気化学的電位ノイズをそれぞれ測定する手段並びに電気化学的電流ノイズ測定値及び電気化学的電位ノイズ測定値から演算処理によって腐食量を算出する手段を具備してなることを特徴とする非水系有機液中における腐食測定装置を指す。
【００２２】
【実施例】
以下に、実施例及び比較例を挙げて本発明を更に具体的に説明するが、本発明はその要旨を越えない限り実施例に限定されるものではない。
【００２３】
実施例１
図１に示す装置を用い、且つ金属電極（センサー）の表面を酸化物被膜を形成させたものを用いて、有機溶媒中に浸漬し、電流計４と電位計５によって電流、電位の変化を測定した。図３はその結果を示すものであって、有機溶媒中に水分がない場合には電流、電位はそれぞれ０（Ａ），０（Ｖ）を示しているが、これに水分を添加した場合には電流、電位がそれぞれ変化し、腐食の進行程度が測定されることが分る。
図４は有機溶媒流れ中で測定した結果であり、電流、電位の変化の挙動が測定されており、これのデータより腐食の進行が測定できる。
【００２４】
比較例１
実施例１において、金属電極表面を酸化物被膜を全く形成させずに実施したこと以外は同様にして行なった。その結果、図５においては、有機溶媒に水分を添加しても電流、電位の変化は見られなかった。図６は図４に用いたものと同じ有機溶媒を用いた場合の電流、電位の変化を示すものであるが、電流、電位は全く変化していない。
【００２５】
【発明の効果】
本発明の方法によれば、化学プラント等の有機液中における金属材料の腐食を信頼性高く、迅速に且つ簡便に測定することができる。
【図面の簡単な説明】
【図１】電気化学的測定法の原理を示す図。
【図２】電流及び電位の変化を示す図。
【図３】水分滴加した有機溶媒中における錆センサーの挙動を示す図。
【図４】有機溶媒中における錆センサーの挙動を示す図。
【図５】水分滴加した有機溶媒中における通常センサーの挙動を示す図。
【図６】有機溶媒中における通常センサーの挙動を示す図。
【符号の説明】
１ センサー
２ センサー
３ センサー
４ 電流計
５ 電位計[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for measuring corrosion of a metal material in a non-aqueous organic liquid and a measuring apparatus therefor. Specifically, the present invention relates to a method for measuring corrosion of a metal material in a non-aqueous organic liquid by an electrochemical measurement method (hereinafter sometimes referred to as an electrochemical noise method) and a measurement apparatus therefor.
According to the method of the present invention, corrosion of a metal material in contact with an organic liquid in a chemical plant or the like can be measured with high reliability, quickly, and simply.
[0002]
[Prior art]
In a chemical plant, etc., the metal surface inside the device that comes into contact with the plant liquid fluid made of organic matter, for example, internal metal surfaces such as reactors, distillation towers, tanks (storage tanks), heat exchangers, etc., and the connection between them Corrosion of the metal material often becomes a problem on the inner metal surface of the metal pipe. For example, in the internal piping of a heat exchanger, it is known that the portion in contact with the fluid becomes a so-called heat transfer surface, and thus is susceptible to corrosion. The corrosion rate or corrosion tendency of the surface must be confirmed.
In general, as a method for measuring corrosion of this type of metal material, a weight reduction measurement method, an electric resistance measurement method, an electrochemical measurement method (noise method), and the like are conventionally known.
[0003]
Among these, for the weight loss measurement method (also called the coupon method or immersion test method), a sample test piece (strip coupon) made of the same material as the surface of the metal to be measured is placed in a corrosive test fluid. The specimen is immersed for corrosion to advance (the specimen specimen itself decreases in weight with the corrosion), and after a certain period of time (usually about 30 to 90 days), the specimen specimen before and after the immersion. This is a means for obtaining the average corrosion rate (corrosion degree) during the test period from the corrosion weight loss (mass difference).
In the case of this method, (a) the corrosion rate cannot be measured instantaneously (in real time), (b) it may take a relatively long time to obtain a measurement result, and the response may be too late. c) There are disadvantages such as inability to measure local corrosion.
[0004]
As for the electrical resistance measurement method, the specimen specimen is immersed in a corrosive test fluid and the corrosion progresses (the electrical resistance value increases corresponding to the decrease in the cross-sectional area of the specimen test itself accompanying the corrosion). In addition, the electrical resistance value of the sample test piece is measured at regular intervals, and the average corrosion rate at the corresponding time is obtained from the measured value gradient.
In this method, (a) the corrosion rate cannot be measured instantaneously (in real time), (b) the measurement sensitivity is low, the influence of temperature is large, and the measurement cannot be performed at a high temperature, (c) There are disadvantages such as inability to measure local corrosion.
[0005]
An electrochemical noise method is known as a method for improving these disadvantages. This method measures the coupling current and electrochemical potential noise between electrodes consisting of two specimen specimens of the same metal surface immersed in a corrosive fluid, and compares both of them to determine the surface of the metal surface. It is a means of measuring corrosion.
[0006]
[Problems to be solved by the invention]
However, with regard to the electrochemical noise method, when the corrosive fluid is a non-aqueous organic liquid, the electrolyte in the organic liquid does not adhere to the surface of the metal electrode as long as the electrolyte in the organic liquid does not adhere to the surface of the metal electrode. Since a circuit is not formed, there is a problem that corrosion measurement cannot be performed.
An object of the present invention is to provide a method and an apparatus for measuring the corrosion state of the surface of a metal material in a non-aqueous organic liquid with high reliability, quickly and simply by an electrochemical noise method.
[0007]
[Means for Solving the Problems]
As a result of intensive studies in view of such circumstances, the inventors of the present invention have made it possible to selectively form an oxide in the organic liquid on the surface of the metal electrode that is immersed in the organic liquid in advance. It was found that an electrical circuit was formed between the electrodes and corrosion could be measured, and the present invention was completed.
[0008]
That is, the gist of the present invention is as follows.
1. Each electrode is exposed to corrosion conditions in the same non-aqueous organic liquid as the object to be measured, with the same material as the metal surface of the object to be measured and oxides formed on the surface. 1. A method for measuring corrosion in a non-aqueous organic liquid, characterized in that electrochemical current noise and electrochemical potential noise are measured, and the amount of corrosion is calculated by arithmetic processing. A plurality of electrodes having the same material as the metal surface to be measured for corrosion, means for forming an oxide on the metal surface of the electrode, and exposing the electrode formed with the oxide to a corrosive condition in a non-aqueous organic liquid Means for measuring the electrochemical current noise and electrochemical potential noise between the electrodes, respectively, and means for calculating the amount of corrosion by arithmetic processing from the electrochemical current noise measurement value and the electrochemical potential noise measurement value. An apparatus for measuring corrosion in a non-aqueous organic liquid, comprising:
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
(Corrosion measurement method)
The corrosion measurement method of the present invention is the same for the corrosion of a metal material in a non-aqueous organic liquid, using a plurality of metal electrodes having the same material as the metal surface to be measured and having oxides formed on the surface. Measured under the corrosive conditions of
[0010]
Here, the non-aqueous organic liquid refers to a non-aqueous organic liquid, and specific examples thereof include a plant liquid containing a raw material, a reaction product, or a solvent in a chemical plant.
Moreover, although it does not specifically limit about a metal, As a specific example, carbon steel, stainless steel, etc. can be mentioned, for example.
[0011]
Plant liquids composed of non-aqueous organic liquids in chemical plants often contain very little electrolyte. If there is very little electrolyte, such as water, in this non-aqueous organic liquid, the electrolyte gradually adheres to the surface of the base material of the device, and chloride ions dissolve into the electrolyte, causing corrosion on the surface of the base metal. To do.
[0012]
When measuring this corrosion by the electrochemical noise method, even if the electrolyte in the organic liquid adheres to the base metal surface of the device, it does not adhere to the surface of the metal electrode for corrosion measurement. Corrosion cannot be measured because it does not form.
[0013]
In the measurement method of the present invention, when an oxide is formed on the surface of a metal electrode that is a sensor, the electrolyte in the organic liquid is selectively attached to the presence of the oxide, and the electrode is electrically connected. Corrosion measurements are possible because the circuit is formed.
[0014]
That is, in the present invention, it is important to form an oxide on the surface of the metal electrode. Further, the method for forming the metal oxide is not particularly limited, and may be applied to the surface of the metal electrode by a method of leaving the metal electrode surface in an oxidizing atmosphere for a predetermined time or a method of leaving the metal electrode surface in an air atmosphere for a predetermined time. An oxide film can be formed.
Note that the oxide of the metal electrode itself is an insulator and does not cause an electrical short circuit or the like.
[0015]
Next, a method for measuring corrosion of a metal material by an electrochemical noise method is described in JP-A-9-297117.
In FIG. 1, three measurement electrodes made of the same material on a metal surface to be measured for corrosion and having an oxide formed on the surface thereof are immersed in a measured corrosive solution made of a non-aqueous organic substance. Between the first electrode 1 and the second electrode 2, a current measuring circuit having a substantially zero internal resistance, a so-called non-resistance ammeter 4 is connected, and between the second electrode 2 and the third electrode 3. Is connected to an electrometer 5 that can measure a signal voltage without affecting the electrode side.
[0016]
In this state, a coupling current is generated between the electrode 1 and the electrode 2 in accordance with the progress of corrosion on the surface of each electrode, and the coupling current is measured by the ammeter 4. The potential difference between the electrode 2 and the electrode 3 is measured by the electrometer 5. FIG. 2 shows changes in current and potential measured by the ammeter 4 and the electrometer 5. From these measurement results, the corrosion rate is calculated by the following equation.
[0017]
[Expression 1]

[0018]
Here, ΔE is a potential change amount ΔI, and a current change amount R is an electrochemical resistance of corrosion.
[0019]
[Expression 2]
Corrosion rate = K x R
[0020]
Here, K is a coefficient determined by the metal material and fluid properties, and can be obtained by back calculation from the weight loss of the metal test piece, or can be obtained by measurement.
[0021]
(Corrosion measuring device)
The corrosion measuring apparatus of the present invention includes a plurality of electrodes having the same material as a metal surface to be measured for corrosion, a means for forming an oxide on the metal surface of the electrode, and an electrode formed with the oxide as a non-aqueous organic material. Means for exposing to corrosive conditions in liquid, means for measuring electrochemical current noise and electrochemical potential noise between the electrodes, and calculation from electrochemical current noise measurement value and electrochemical potential noise measurement value It means a device for measuring corrosion in a non-aqueous organic liquid characterized by comprising means for calculating the amount of corrosion by treatment.
[0022]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the examples unless it exceeds the gist.
[0023]
Example 1
The apparatus shown in FIG. 1 is used, and the surface of the metal electrode (sensor) having an oxide film formed thereon is immersed in an organic solvent. The ammeter 4 and the electrometer 5 change the current and potential. It was measured. FIG. 3 shows the results. When there is no moisture in the organic solvent, the current and potential are 0 (A) and 0 (V), respectively. It can be seen that the current and potential change, and the degree of progress of corrosion is measured.
FIG. 4 shows the results of measurement in an organic solvent flow, in which the behavior of changes in current and potential is measured, and the progress of corrosion can be measured from the data.
[0024]
Comparative Example 1
In Example 1, it carried out similarly except having implemented without forming the oxide film on the metal electrode surface at all. As a result, in FIG. 5, no change in current and potential was observed even when water was added to the organic solvent. FIG. 6 shows changes in current and potential when the same organic solvent as that used in FIG. 4 is used, but the current and potential are not changed at all.
[0025]
【The invention's effect】
According to the method of the present invention, corrosion of a metal material in an organic liquid such as a chemical plant can be measured with high reliability, quickly and simply.
[Brief description of the drawings]
FIG. 1 is a diagram showing the principle of an electrochemical measurement method.
FIG. 2 is a graph showing changes in current and potential.
FIG. 3 is a diagram showing the behavior of a rust sensor in an organic solvent to which moisture is added.
FIG. 4 is a diagram showing the behavior of a rust sensor in an organic solvent.
FIG. 5 is a diagram showing the behavior of a normal sensor in an organic solvent to which moisture is added.
FIG. 6 is a diagram showing the behavior of a normal sensor in an organic solvent.
[Explanation of symbols]
1 Sensor 2 Sensor 3 Sensor 4 Ammeter 5 Electrometer

Claims (4)

  A state in which a plurality of electrodes having the same material as the metal surface of the corrosion measurement object and an oxide of a metal electrode formed on the surface are exposed to corrosion conditions in the same non-aqueous organic liquid as the measurement object A method for measuring corrosion in a non-aqueous organic liquid, characterized in that electrochemical current noise and electrochemical potential noise between the respective electrodes are respectively measured and an amount of corrosion is calculated by arithmetic processing.   A plurality of electrodes having the same material as the metal surface to be subjected to corrosion measurement, means for forming an oxide of the metal electrode on the metal surface of the electrode, and the electrode formed with the oxide under corrosive conditions in a non-aqueous organic liquid The amount of corrosion is calculated by arithmetic processing from the means for exposing to the electrode, the means for measuring the electrochemical current noise and the electrochemical potential noise between the electrodes, respectively, and the electrochemical current noise measurement value and the electrochemical potential noise measurement value. An apparatus for measuring corrosion in a non-aqueous organic liquid, characterized by comprising: The corrosion measurement method according to claim 1, wherein the arithmetic processing is performed by the following formula.
[Expression 1]
ΔE / ΔI = R (Formula 1)
(In Formula 1, ΔE represents the amount of change in potential, ΔI represents the amount of change in current, and R represents the electrochemical resistance of corrosion.)
[Expression 2]
Corrosion rate = K x R (Formula 2)
(In Equation 2, K represents a coefficient determined by the metal material and fluid properties, and R represents the electrochemical resistance of corrosion.) The corrosion measurement apparatus according to claim 2, wherein the arithmetic processing is performed by the following formula.
[Equation 3]
ΔE / ΔI = R (Formula 1)
(In Formula 1, ΔE represents the amount of change in potential, ΔI represents the amount of change in current, and R represents the electrochemical resistance of corrosion.)
[Expression 4]
Corrosion rate = K x R (Formula 2)
(In Equation 2, K represents a coefficient determined by the metal material and fluid properties, and R represents the electrochemical resistance of corrosion.)

Images