JPH07103879A - Method and apparatus for corrosion test - Google Patents

Abstract

PURPOSE:To inspect the corroded state with high reproducibility for various types of gas over wide ranges of concentration and temperature by supplying a predetermined quantity of corrosive liquid and evaporating the liquid completely and then mixing the vapor with the atmospheric gas thereby conditioning the corrosion test gas of specified concentration and temperature. CONSTITUTION:A corrosive liquid (e.g. aqueous solution of hydrochloric acid) is fed by a fixed quantity pump 12 from a storage tank 11 to an evaporator 13 where the liquid is evaporated completely to produce a corrosive gas which is then fed to a mixer 16. At the same time, an atmospheric gas (e.g. the air) is fed to the mixer 16 through a flow rate regulation valve 15. The mixer 16 comprises a double tube filled with a filter 17 for facilitating the heating and cooling. A heat medium controlled at a specified temperature is circulated from a heat medium storage tank 21 to the outer tube through a heat medium circulation pump 22 and the corrosive gas introduced to the inner tube is mixed with the atmospheric gas and heated to produce a corrosion test gas. It is fed to a test section 18 and caused to react on a test piece 19 which is taken out upon elapse of a predetermined time thus inspecting the extent of corrosion and the presence of stress corrosion crack.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion test method and apparatus. More particularly, it relates to a method and apparatus for testing gas phase corrosion and stress corrosion cracking.

[0002]

2. Description of the Related Art There are many corrosive liquids and gases in a chemical plant, which damage equipment and pipes made of metal materials or the like. In particular, many cracks and corrosions due to a small amount of hydrochloric acid gas and the like occur, and most of the cracks are stress corrosion cracks.

As a test method for investigating the cause of the cracks and corrosion and selecting a material, an actual machine test method in which a test piece is incorporated into an actual machine in the field, and an apparatus as shown in FIG. A static immersion corrosion test method is known in which a piece is placed in a liquid or a gas.

[0004]

However, it is difficult to change the conditions in the actual machine test method, and the test piece is often taken in and out only at rest, so the test frequency is reduced, It takes a long time to produce results. Further, in the stationary immersion corrosion test method, it is difficult to keep the conditions such as the concentration constant, and the range of conditions that can be changed is narrow, so that the test especially in a dilute gas is difficult.

In view of such circumstances, the present inventor has conducted extensive studies on a corrosion test method and an apparatus therefor, and as a result, supplied a fixed amount of a corrosive liquid, evaporated all of it, mixed it with an atmospheric gas, and conducted a corrosion test gas of a predetermined concentration and temperature. It was found that a test can be performed in a wide range with good reproducibility by adjusting the temperature and using a device for holding the test piece in the gas, and the present invention has been completed.

[0006]

That is, according to the present invention, a corrosive liquid is continuously supplied in a fixed amount, and the whole amount of the corrosive liquid is heated and evaporated to form a corrosive gas. Is continuously supplied in a fixed amount and mixed, and heated or cooled by a circulating heating medium having a predetermined temperature to obtain a corrosion test gas having a predetermined concentration and temperature, and a test piece is held in the corrosion test gas. A corrosion test method and its equipment.

The corrosive liquid is not particularly limited as long as it can be evaporated, and inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid and nitric acid, formic acid, acetic acid, propionic acid, butyric acid, acrylic acid, Examples thereof include organic acids such as methacrylic acid.

As the atmosphere gas, nitrogen, oxygen, air, hydrogen, carbon monoxide, carbon dioxide, sulfur dioxide, sulfur trioxide, inorganic gas such as NOx gas, carbonization of methane, ethane, propane, ethylene, propylene, isobutylene, etc. Examples thereof include hydrogen gas.

Whether the corrosive gas is supplied as a corrosive liquid to be vaporized or supplied as an atmospheric gas is appropriately determined in consideration of the concentration to be used and the ease of adjustment thereof.
Usually, a corrosive liquid is often supplied because the test is often performed under a condition where the concentration of corrosive gas is low. In addition, in order to match the actual conditions, the compounds that actually exist (for example, benzene, toluene, methanol, etc.) are separately supplied and evaporated in the same manner as the corrosive liquid, and then mixed with the mixed gas of the corrosive gas and the atmospheric gas. May be.

Next, an example of an embodiment of the present invention will be described with reference to FIGS. 1 and 2. A corrosive liquid having a concentration set in consideration of the test conditions in the storage tank 11 is quantitatively supplied to the evaporator 13 by the metering pump 12, and the whole amount is evaporated to generate a corrosive gas, which is supplied to the mixer 16. At the same time, the atmosphere gas is quantitatively supplied to the mixer by the flow meter 14 and the flow rate adjusting valve 15, and the corrosive gas and the atmosphere gas are mixed.

The mixer 16 consists of a double pipe, the inner pipe has a filler 17, and the outer pipe circulates a heat medium controlled from a heat medium storage tank 21 to a predetermined temperature by a heat medium circulation pump 22. The corrosive gas and the atmospheric gas are supplied to the inner tube and mixed sufficiently, and the corrosion test gas obtained by mixing is heated or cooled to be a corrosion test gas having a predetermined concentration and temperature. The heat medium used is not particularly limited, but silicon oil or the like is usually used, and hot water is also used at about 90 ° C. or lower.

The filler 17 facilitates mixing of the corrosive gas and the atmospheric gas and heating or cooling of the obtained corrosion test gas, and is not particularly limited as long as it is an inert material. Usually, glass Raschig rings are used.

In FIG. 1 and FIG. 2, the evaporator 13 is provided in the heat medium circulating in the outer tube of the mixer, but the method is not limited to this, and it may be provided outside and heated by electric heat or the like. good. Further, a preheating section for the corrosive liquid and / or the atmospheric gas may be provided in the heat medium storage tank and / or the circulating heat medium. In FIGS. 1 and 2, the pipes to the mixer for corrosive gas are lengthened, and the pipes for atmospheric gas are made to be a serpentine pipe, and these are used as the preheating section.

A corrosion test section 18 is provided above the mixer 16. This corrosion test section is composed of a double tube consisting of an inner tube holding the test piece 19 and the temperature measuring terminal 20 and an outer tube through which a heat medium circulates. The corrosion test gas of a predetermined concentration and temperature from the mixer is fed into the inner tube. And expose the test piece for a predetermined time to conduct the test. During this time, check the test temperature with the temperature measurement terminal. The mixer and the outer tube of the corrosion test section may be integrated or separate. The mixed gas is cooled by the cooler 23 and discarded, and the produced drain is received by the receiver 24.

After testing for a predetermined time, the corrosion test piece is taken out and the corrosion degree and the presence or absence of stress corrosion cracking are checked. Also, check the supply rate of the corrosive liquid from the reduction of the corrosive liquid in the storage tank.

In FIG. 2, a second mixer 25 and a second corrosion test section 27 are provided above the above corrosion test section. The second mixer also comprises a double pipe, the inner pipe has the filler 26, and the outer pipe circulates the second heat medium controlled to a predetermined temperature from the heat medium storage tank 30 by the heat medium circulation pump 31. Then, a corrosion test gas from below is supplied to the inner pipe and heated or cooled by a heat medium to adjust the corrosive gas to a predetermined temperature.

The second corrosion test section also comprises a double tube of an inner tube holding the test piece 28 and the temperature measuring terminal 29 and an outer tube through which the heat medium circulates, and has a predetermined concentration and temperature from the second mixer. The corrosion test gas is passed through the inner tube, and the test piece is exposed for a predetermined time to perform the test. During this time, check the test temperature with the temperature measurement terminal. The temperature of the second corrosion test section can be freely set to be higher or lower than that of the lower corrosion test section.

[0018]

EFFECTS OF THE INVENTION By using the method and apparatus of the present invention, it is possible to easily and accurately measure a wide range of conditions such as various gases, concentrations, and temperatures, especially for dilute corrosive gases, and even at temperatures above the boiling point. Corrosion tests can be performed.

[0019]

EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Example 1 Using the apparatus shown in FIG. 2, SUS304, SUS316
For each (spot-welded test piece), an aqueous hydrochloric acid solution was used as the corrosive liquid, and air was used as the atmosphere gas, and the temperature of the lower heating medium (silicon oil) was 120 ° C.
A corrosion test was performed in dilute hydrochloric acid gas for 168 hours under the normal pressure of the second heat medium (warm water) at 80 ° C. Table 1 shows the concentration, supply amount, and supply amount of air of the hydrochloric acid aqueous solution, and Table 2 shows the corrosion test results. No16-18 is the reproducibility test of No11. FIG. 3 shows the corrosion test results of SUS304 at 80 ° C. It can be seen that water has a greater influence than hydrochloric acid as a factor of stress corrosion cracking. The lower limit is P (H ₂ O) = 10000
It is 20,000 Pa.

[0021]

[Table 1]

[0022]

[Table 2]

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an embodiment of the present invention.

FIG. 2 is a diagram showing another example of the embodiment of the present invention.

FIG. 3 is a diagram showing the presence or absence of stress corrosion cracking for SUS304 at 80 ° C.

FIG. 4 is a view showing a conventional stationary immersion corrosion device.

[Explanation of symbols]

 11 Storage tank 12 Metering pump 13 Evaporator 14 Flowmeter 15 Flow control valve 16 Mixer 17 Filler 18 Corrosion test section 19 Test piece 20 Temperature measurement terminal 21 Heat medium storage tank 22 Heat medium circulation pump 23 Cooler 24 Receiver 25 Second Mixer 26 Filler 27 Second corrosion test part 28 Test piece 29 Temperature measuring terminal 30 Heat medium storage tank 31 Heat medium circulation pump 101 Test vessel 102 Test solution 103 Heat medium 104 Thermometer 105 Cooler 106 Test piece

Claims (4)

[Claims] 1. A constant amount of corrosive liquid is continuously supplied, and the whole amount is heated and evaporated to form a corrosive gas, and a predetermined amount of atmospheric gas is continuously supplied in constant amount to the corrosive gas and mixed. In addition, the corrosion test method is characterized in that a corrosion test gas having a predetermined concentration and temperature is heated or cooled by a circulating heating medium having a predetermined temperature, and a test piece is held in the corrosion test gas. 2. The corrosion test method according to claim 1, wherein the corrosive liquid is an aqueous hydrochloric acid solution, and the atmosphere gas is nitrogen gas or air. 3. A corrosion test apparatus comprising the following (1) to (5). (1) Storage tank and metering pump for quantitatively supplying the corrosive liquid (2) Evaporator for evaporating the entire corrosive liquid supplied to generate corrosive gas (3) For the corrosive gas And a flow rate control valve for supplying a predetermined amount of atmospheric gas (4) Filling for mixing the corrosive gas and the atmospheric gas and heating or cooling to obtain a corrosion test gas of a predetermined concentration and temperature Mixer consisting of a double tube having an inner tube through which a gas passes and an outer tube through which a heat transfer medium circulates (5) Corrosion test gas located above the mixer and holding a corrosion test piece and a temperature measurement terminal Corrosion test section consisting of a double tube with an inner tube through which heat flows and an outer tube through which a heat medium circulates 4. An inner pipe having a filler and a heating medium for circulating (1) heating or cooling the corrosion test gas to adjust the temperature of the corrosion test gas are circulated above the corrosion test section. A second mixer consisting of a double tube of an outer tube and (2) an inner tube and a heating medium which are located above the second mixer and which hold a corrosion test piece and a temperature measuring terminal and through which a corrosion test gas passes The corrosion test apparatus according to claim 3, further comprising a second corrosion test section including a double tube of an outer tube.