JPS61251762A - Simple measuring method for passivation effect of metal - Google Patents

Abstract

PURPOSE:To make possible the quick and sure measurement by brining the other one electrode which consists of the same material as the material of an object to be inspected and is held in an activated stage into contact with the object to be inspected through filter paper or the like impregnated with a normal concn. of electrolyte. CONSTITUTION:The relatively flat surface of the object 1 which is made of, for example, SUS304 stainless steel and is to be inspected is selected and the filter paper 3 impregnated with 1N concn. of sulfuric acid soln. as the electrolyte is pressed onto said surface and further the electrode 2 made of SUS304 stainless steel which is the same material as the above-mentioned body is superposed thereon after the surface thereof is throughly activated by polishing the surface with emery paper to form an electric circuit. The value indicated on a potentiometer 4 is measured with lapse of time and is compared with the value obtd. preliminarily with the object treated under the same conditions as for the standard object to be inspected. The numerical value of the initial potential thereof and the sustaining time of the potential are compared by which the discrimination of the passivation effect is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simply measuring the presence or absence of passivation of a metal device and its degree, and is particularly effective when used in conjunction with stainless steel.

Conventionally, some metal materials, particularly stainless steel, have been subjected to equipment treatment that considers passivation during the manufacturing process in order to improve the corrosion resistance of equipment, but during secondary processing, cutting, polishing, etc. It is a well-known fact that mechanical grinding or chemical treatments such as pickling, degreasing, and washing activate the passivation treatment equipment, making it more susceptible to corrosion and rusting. However, on the other hand, Stainless steel has the property of becoming passivated by itself to the extent that it becomes passive if it is left in clean air for a long period of time, but this degree is not sufficient and it requires a long period of time. For.

In order to safely maintain stainless steel products during transport from the processing factory to the site of use, or between installation at the factory and operation, appropriate passivation treatment is required depending on the purpose and period. It has been said that

The passivation treatment method for this purpose is to add dichromate to nitric acid, dichromate to caustic soda, and permanganate to caustic soda and heat it to room temperature or about 80℃. Generally recommended is a method of immersing the product in a soaked state for about 30 minutes to 2 hours.

However, as a means of determining the degree of activation or passivation as described above, conventional methods have been to use an Amagi electrode as one electrode in a sulfuric acid solution of 1 normal concentration, and place the analyte to be determined at one point. A method was proposed in which each electrode was immersed in a container and a potentiometer was placed between the two electrodes to measure the naturally occurring potential, and this method was adopted as the only laboratory method. However, 1. Usually, the container is a beaker, and the test piece is limited to a corresponding size.

It is impossible to directly measure the passivation effect when the test object is a product, or especially for a structure that cannot be immersed in the passivation treatment solution as described above. This method has drawbacks such as being impractical in the field because it requires specific equipment and techniques, such as a sulfuric acid solution and Amagi electrodes, which are easily damaged and inconvenient to handle.

The present invention was devised to improve the shortcomings of the known methods as described above, and uses a test object made of a metal material such as stainless steel as a single pole directly.

After activating another pole made of the same material as the test object, the test object is transferred to the test object device via a water-absorbing paper sheet material such as F paper impregnated with an electrolytic solution that dissolves the test object. The passivation effect of the metal can be determined from the relationship between the predetermined degree of passivation and the spontaneous potential by placing a potentiometer between the two electrodes and measuring the spontaneous potential. It is characterized by being able to measure.

According to its nature, it has extremely simple equipment and operation.

This makes it possible to non-destructively and extremely easily measure an object of any shape on-site.

Now, a preferred embodiment of the present invention will be described based on the drawings. 1 is 8US 304 which has been completely passivated.
A specimen made of stainless steel, 2 an electrode made of SUB 304 selected as the same material as the specimen, 3 a P paper as a water-absorbing sheet material impregnated with a sulfuric acid solution of a certain concentration, 4
5 is a potentiometer, and 5 is a conductive wire with one end connected to the electrode 2 and the other end connected to the potentiometer 4.

Reference numeral 6 denotes a conductive wire having one end connected to an arbitrary location on the subject 1 and the other end connected to the potentiometer 4.

Now, among such devices, we selected a relatively flat device with a SUB 304 stainless copper specimen 1.

On top of that, P paper 3 impregnated with 1N sulfuric acid solution as an electrolyte is applied, and on top of that, electrode 2 made of 19U8304 is stacked after polishing the device with emery paper and activating it sufficiently. Form an electrical circuit. Immediately measure the indicated value of the potentiometer 4 over time, and activate the material and its device in advance.

The passivation effect can be determined by comparing standard specimens prepared with various degrees of inactivation and treated under the same conditions, and comparing the initial potential value and duration of the potential. good.

In this case, the reaction occurs on both the front and back sides of P paper impregnated with sulfuric acid at a predetermined concentration.

The object and the electrodes form a so-called primary battery using a sulfuric acid solution as an electrolyte, but the stronger the passivation film, the better the corrosion resistance, and if one electrode is also completely passivated, the same effect will occur. Coatings that exhibit corrosion resistance do not generate an electromotive force. However, as mentioned above, the electrode device has been fully activated in advance.

Since one of the specimens has been completely passivated, the initial potential between the two electrodes shows a high value of 600 H#V or more, and over time the passive film of the specimen 1 becomes As it was eroded and dissolved by the sulfuric acid, the potential gradually decreased as it completely dissolved and disappeared, and finally dropped to nearly zero after about 3 minutes.

In this way, the present application makes measurement possible by selecting the same material as the test object for the other electrode and setting it in an activated state.The high initial potential means that the material is dense and relatively thick. This indicates that a chemical film has been formed, and the persistence of the potential indicates that the formed film has high strength and corrosion resistance.

In general, the passive region of stainless steel is +200+11V to +1000 #lV at the natural electrode potential of the Amagi electrode.
Although the sulfuric acid solution used in the measurement in the examples of the present invention was used, it is not necessarily limited to this, and if the concentration is higher than this, the dissolution time of the passive film is faster, so the initial potential may be lower. The duration is short, and conversely, if it is thinner than this, the duration will be longer, so it is only necessary to set the concentration appropriately and compare it with the standard specimen.Also, the type of electrolyte should be determined depending on the metal being tested. Depending on the ma, any corrosive and reducing agent such as hydrochloric acid may be used in addition to sulfuric acid.

On the other hand, if the material of the electrode is different from that of the specimen, a so-called primary battery will be formed for each combination of materials regardless of passivation, so a potential will be generated for each combination. It will be done.

However, in this application, since we always use an electrode made of the same material as the test object, we do not show the potential caused by the formation of a primary battery that occurs between different materials, and measurements are always made in an activated state. Since this is an essential condition, if the specimen is passivated as mentioned above, the
A spontaneously generated potential of about 0.00111V is obtained, but if the device under test is also in an activated state, no potential is generated at all.

In other words, when the subject is in an activated state, no spontaneously generated potential is observed; on the other hand, when the subject is in a passivated state, the potential is large depending on the degree, and the potential changes over time depending on the thickness of the passivated film. It is characterized by the fact that the potential attenuates and eventually approaches zero, making it easy to measure the extent of this.

In addition, as a means of activating the electrodes during measurement,
In addition to polishing using an emery vapor as in the above embodiment, the same effect can also be obtained by immersing it in a reducing acid solution such as dilute sulfuric acid or hydrochloric acid for a short time. .

Therefore, in carrying out the measurement method of the present invention, it is not only easy to carry out without requiring any specialized knowledge or skill, but also to measure parts that have already been installed, or to measure a large number of parts. It has many advantages over known methods, such as being able to immediately respond to various on-site requirements such as measuring objects, and being extremely quick and easy to carry out without damaging products or materials. 1 According to the present invention, a metal object such as stainless steel is directly used as one electrode, and the other electrode made of the same material as the object and in an activated state is impregnated with an electrolytic solution such as sulfuric acid at a specified concentration. The test object is brought into contact with the test object via a water-retaining paper sheet such as paper, and a potentiometer is placed between the two electrodes to measure the naturally occurring potential and compared with a standard test object, or the test object is prepared in advance by a standard test object. By comparing the relationship between the degree of passivation determined for WI and the naturally occurring initial potential and the state of decay of this potential over time, it is possible to evaluate the passivation effect of metal specimen devices on-site and extremely easily. The present invention is extremely useful industrially because it enables rapid, reliable, and easy on-site measurement of any shape of a specimen using the same equipment and operation.

[Brief explanation of the drawing]

The drawing is a schematic diagram illustrating the principle of the method of the invention. 1... Subject, 2... Electrode, 3... F paper, 5...
・Potentiometric needle.

Claims (1)

[Claims] The object to be measured is directly connected to one electrode, and the other electrode, which is made of the same material as the object and is in an activated state, is connected through a water-absorbing paper material impregnated with an electrolyte that dissolves the object. Each is brought into contact with a metal specimen device, and a potentiometer is interposed between the two electrodes to form an electric circuit, the spontaneously generated potential between the two electrodes is measured, and the degree of passivation of the metal is determined from the change in the generated potential. A simple method for measuring the passivation effect of a metal, characterized in that: