JP2006030117A - Heat-resistant and corrosion-resistant high performance sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that sensor sensitivity is directly affected by the conventional sensor portion, which is made by using a noble metal such as tantalum or a cladding plate composed of stainless steel and tantalum to a diaphragm to weld the sensor portion and then a heat affected portion by a separate material or welding is left by the diaphragm itself. <P>SOLUTION: A heat-resistant and corrosion-resistant high performance sensor is obtained by glass coating under thickness control up to a nano-order, on the surface of the sensor portion made from a heat-resistant and corrosion-resistant metallic material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to heat resistance and corrosion resistance of a diaphragm substrate of a pressure sensor for measuring the pressure when a corrosive solution or gas is handled in the general chemical industry field, nuclear field, space / aviation field, marine field, etc. is there.

  Conventionally, methods have been devised to increase heat resistance by thermally insulating metal substrate materials or to coat with ceramics or refractory metals as an anticorrosion measure, but it is compatible with a wide range of corrosive solutions and gases such as strong acids and strong alkalis. In addition, there is no coating method that does not impair the material composition and structure of each sensor part such as a pressure sensor and a temperature sensor that require high accuracy, and its measurement sensitivity and durability.

  In the conventional method, when the above coating material is applied to the sensor base metal substrate, the reaction layer is formed between the substrate and the coating by high temperature, high pressure and chemical reaction. This is because the accuracy is lowered, or the base material is altered by high-temperature treatment.

(A) Reduction of influence on metal base material during coating construction As a typical example, FIG. 1 shows a high-temperature corrosion-resistant diaphragm pressure sensor. Since the pressure measurement sensitivity of this sensor is determined by the rigidity and displacement of the SUS thin diaphragm (diaphragm material) in the figure, it is necessary to apply a corrosion-resistant coating to the surface of the diaphragm in contact with the liquid. However, in the conventional method, a noble metal such as tantalum is used for the diaphragm, or a sensor part is mainly formed by high temperature welding using a cladding plate of SUS and tantalum, but in this case, the diaphragm itself is made of a different material or Since the heat affected zone by welding is left in the sensor portion, it directly affects the sensor sensitivity. Therefore, a coating method that does not generate a reaction layer at a low temperature on the surface of the SUS diaphragm is desired.
(I) Inorganic reaction stability Since it has been known that inorganic quartz and silica quartz have the highest stability for high-temperature use, the silica film on the metal surface at a low temperature has been known. A technology that can be formed is required.
(C) Film thickness stability of the thin film In order not to impair the accuracy of the diaphragm of FIG. 1, it is necessary to uniformly produce a coating thin film that does not affect the rigidity of the diaphragm as much as possible in the film formation region.
(D) Densification Similarly, in order not to impair the accuracy of the diaphragm of FIG. 1, it is necessary to uniformly form a dense and uniform coating thin film that does not affect the diaphragm rigidity as much as possible in the film formation region.
(E) Coating on the metal surface Although it is necessary to coat the glass material having the above characteristics (a) to (d) on the surface of the heat-resistant metal sensor, the thermal expansion coefficient of the glass is hardly high. Since the thermal expansion coefficient of the metal sensor base material is quite large, peeling and cracking have occurred between the metal substrate and the glass in the conventional method.
(F) Price When conventional noble metals such as tantalum were used, there was a drawback that material costs and construction costs were increased.
(G) Construction and repair In thin film coating, it is desirable to perform repair work regularly because of its reliability. Therefore, there is a need for a technique that can easily recoat damaged sites in the coating area in use.

The present invention is a heat-resistant and corrosion-resistant high-performance sensor that can solve the above problems (a) to (g).
(1) A polysilazane compound or a mixed solution of a polysilazane compound and a polycarbosilane compound that can be converted into silica by heating at high temperature from room temperature to 1000 ° C. in the atmosphere is used as a silica coating coating film precursor.

  (2) For example, the unevenness can be eliminated by polishing and degreasing the surface of the pressure sensor metal diaphragm wetted part side, and a strong bonding thin film can be generated between the silica coating coating film and the metal surface.

(3) In order to control the film thickness to be constant, when applying the above (1) to (2), nano-level film thickness control is possible by spin coating or spraying.
(4) The method of (3) is also easy to repair because it can be used during construction.

(5) The unit cost of the produced film silica is low, and the coating cost can be reduced by the construction method according to (3).
That is, the sensor of the present invention comprises a polysilazane compound, or a polysilazane compound that can be converted to silica by polishing and degreasing the surface of the pressure sensor metal diaphragm wetted part side and heating the surface at a high temperature. Apply a mixed solution with polycarbosilane compounds by spin coating or spray spraying, and heat to high temperature from room temperature to 1000 ° C in the atmosphere, so that the thickness on the metal diaphragm wetted part side is nano-class thickness A controlled silica coating coated thin film was produced.

  According to the present invention, the surface of a conventional heat-resistant alloy can be coated with a chemically stable silica glass, so that various sensors can be used with high accuracy in a high-temperature and high-pressure corrosion environment. Thereby, the reliability and durability of the control sensor in a corrosive environment such as a general chemical plant or the ocean can be remarkably improved.

A case where the heat and corrosion resistance sensor of the present invention is used in a pressure gauge of an HIx circulation test apparatus will be described with reference to FIG.
In the above HIx circulation test equipment, a corrosion sample is installed in this equipment, a hydrogen iodide solution is introduced into the equipment through a high temperature corrosion resistance valve, and the solution is circulated through the equipment using a magnet pump and brought into contact with the sample to cause the corrosion. Observe the degree from the observation port for measurement. The pressure of the hydrogen iodide solution circulating in the apparatus is measured with a high-temperature corrosion-resistant pressure gauge, and a pressure obtained by applying the glass coating of the present invention to a thin diaphragm substrate used as a diaphragm type pressure sensor of this pressure gauge. Sensor is in use.

  The temperature of the solution circulating in the test apparatus is measured with a high temperature corrosion resistance thermometer, and the flow rate is measured with an ultrasonic flow meter. As the circulation pipe constituting the test apparatus, a glass lining straight pipe and a glass lining elbow pipe are used, and Teflon (registered trademark) packing, Ta joint, and the like are provided at necessary portions. Polytetrafluoroethylene (PTFE) is used as the lining or packing material.

  In this test apparatus, when the level of the corrosive solution does not reach the pressure gauge, the gas pressure of the corrosive gas generated from this solution can be measured, and the level of the corrosive solution reaches the pressure gauge. If so, the hydraulic pressure of the corrosive solution can be measured.

  Furthermore, this test device is provided with a corrosion-resistant rupturable plate, which is used as a gas vent for safely protecting the circulation pipes and measuring devices by rupturing the rupturable plate at the time of abnormal pressure increase in the device. It is done.

  FIG. 2 shows a glass thin film coated on the surface of the SUS316 diaphragm wetted part shown in FIG. Fig. 3 shows how this pressure sensor (high-temperature corrosion-resistant pressure gauge) is attached to the HIx circulation test equipment that simulates the hydrogen iodide circulation system of the IS process (closed cycle process that repeatedly uses iodine and sulfur dioxide to produce hydrogen). The pressure and temperature of the hydrogen iodide solution circulated at a high temperature of not lower than ° C. are continuously monitored over 1000 hours. This temperature is measured by placing a thermometer whose surface is coated with glass to prevent corrosion in the solution flow in the circulation pipe.

  The high temperature and corrosion resistant high performance sensor of the present invention can measure the pressure and temperature of sulfuric acid and hydrogen iodide based on high temperature and high pressure in IS hydrogen production process with high accuracy.

It is a figure which shows the structure of a diaphragm type pressure gauge. It is a figure which shows the glass nano thin film coated on the SUS316L diaphragm surface. It is a figure which shows a HIx circulation test apparatus and a glass coating pressure gauge.

Claims (8)

  Heat-resistant and corrosion-resistant high-performance sensor obtained by glass coating on the surface of sensor parts made of heat-resistant and corrosion-resistant metal materials under thickness control down to the nano level.   The sensor according to claim 1, wherein the pressure of a strong acid such as sulfuric acid or hydrogen iodide, a strong alkaline corrosion solution, or the pressure of these corrosive gases can be measured with high accuracy.   The sensor according to claim 1, wherein the temperature of a strong acid such as sulfuric acid or hydrogen iodide, a strong alkaline corrosive solution, or a corrosive gas thereof can be measured with high accuracy.   The sensor according to any one of claims 1 to 3, wherein the service life can be extended by recoating and repairing a damaged part of the glass coating sensor part in use.   The sensor according to any one of claims 1 to 4, further comprising a glass coating that can withstand high temperatures up to 1000 ° C and high pressure environments.   The sensor according to any one of claims 1 to 5, wherein a polysilazane compound and a mixed solution of the polysilazane compound and the polycarbosilane compound are used as a silica coating precursor of the glass coating.   The sensor according to any one of claims 1 to 6, wherein the sensor is obtained by coating the surface of the refractory metal while polishing and degreasing and eliminating impurities in the atmosphere in the coating work environment so that impurities do not enter the coating. The sensor according to claim 6 or 7 obtained by coating the precursor of claim 6 on the sensor part, firing the coating at room temperature to 1000 ° C for 1 to 5 hours, and forming a coating film.