JPH10130810A - Production of titanium oxide coating for corrosion prevention and titanium oxide coating for corrosion prevention - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase adhesion of TiO2 coating to a material to be applied for corrosion prevention, to increase the holdability of the shape of (n) type TiO2 particles and to increase the operability in the case of coating formation by thermally spraying (n) type TiO2 particles on the surface of the material to be applied for corrosion prevention through the method by which they are carried on a plasma flow to produce a melted and solidified layer of TiO2 , thereafter shifting the plasma thermal spraying temp. to a low one and forming its structure so that the ratio of the particles is increased. SOLUTION: In the producing process of (n) type TiO2 coating X, in which plasma current and the flow rate of plasma gas are changed, and (n) type TiO2 particles are welded to the material 1 to be applied for corrosion prevention while the temp. of the plasma flow is substantially reduced, the TiO2 coating X to be produced has a gradient structure shown in the fig. In the initial stage of thermal spraying, by the melting and solidifying of TiO2 , the ratio of the (n) type TiO2 particles reduces, but, as a half-melted layer 3 and a particle layer 4 are formed, the ratio occupied by the (n) type TiO2 particles gradually increases, and finally, the particle layer 4 in which the ratio of the (n) type TiO2 particles layer is increased can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a titanium oxide film for corrosion protection and a titanium oxide film for corrosion protection, and more particularly to a technique for performing corrosion protection on a reactor structural material by utilizing a photoelectrode reaction. It is.

[0002]

2. Description of the Related Art In a light water reactor using water as a coolant, most of the internal structures in a reactor pressure vessel surrounding a reactor core are arranged in high-temperature reactor cooling water, and radiation emitted from the reactor core is emitted. Therefore, the constituent materials have corrosion resistance to the cooling water of the reactor, and special attention has been paid to quality control such as taking into account the effects of water decomposition of radiation.

[0003] For example, Japanese Unexamined Patent Publication No. 07-270592 entitled "Reactor Structural Materials and Corrosion Prevention Method" discloses a method for producing a titanium oxide film for corrosion protection and a technique related to the titanium oxide film for corrosion protection. Techniques related to a method for manufacturing a titanium oxide film used for a structure have been proposed. This technology utilizes the photo-semiconductor properties of the titanium oxide film to generate a non-consumable anodic reaction when irradiated with radiation or Cherenkov radiant light, and the reactor structural material near the titanium oxide film (photo-semiconductor film) The corrosion potential of the surface is lowered to increase the corrosion resistance of the metal.

Further, a titanium oxide film (TiO ₂ film) is produced by spraying Ti particles in an atmosphere containing oxygen.

[0005]

However, it is difficult to efficiently obtain good optical semiconductor characteristics by the method of producing a TiO ₂ film by spraying and oxidizing Ti particles.

[0006] On the other hand, n-type TiO ₂ is expected to have optical semiconductor characteristics. However, in the case of a technique for plasma-spraying n-type TiO ₂ particles, for example, the plasma flow is at a high temperature, so that the n-type TiO ₂ becomes molten. As a result, there remains a problem that the crystal structure of the optical semiconductor is broken and optical semiconductor characteristics are impaired.

[0007] The present invention has been made in view of such problems, and has the following objects. To improve the adhesion of the TiO ₂ film to the material to be protected. The n-type TiO ₂ particles have improved shape retention and n-type Ti 2
To facilitate the production of O ₂ films. Improving workability when forming a TiO ₂ film.

[0008]

Means for Solving the Problems n-type TiO_Two Particles
Sprays on the surface of the material to be protected in a zuma flow
TiO with semiconductor properties_Two When fabricating the film, TiO
_Two The particles are melted to form a molten solidified layer on the material to be protected,
N-type TiO _Two Particles
A particle layer is prepared by welding. In this case
The n-type TiO_Two By supplying only particles, the molten solidified layer and
And both the particle layer and the particle layer. In addition, the table
On the surface, change the plasma spray temperature from high to low
n-type TiO_Two N-type TiO to weld the particles_Two particle
TiO with ratio set continuously or stepwise_Two Film made
Made.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for producing a titanium oxide film for corrosion protection and an embodiment of a titanium oxide film for corrosion protection according to the present invention will be described with reference to FIGS.

FIG. 1 shows an example of a manufacturing process of a titanium oxide film for corrosion protection. In FIG. 2, reference numeral 1 denotes a material to be protected, 2 denotes a melt-solidified layer, 3 denotes a semi-molten layer, 4 denotes a particle layer (n-type TiO ₂ particle layer), and X denotes a TiO ₂ film.

[S1: Production of n-type TiO ₂ particles]
N-type TiO ₂ particles having a particle size of several μm to several tens μm are manufactured in advance.

[S2: Supply of n-type TiO ₂ Particles] The n-type TiO ₂ particles produced in S1 are supplied to a plasma spraying apparatus.

[S3: Plasma spraying] Ar gas is used as a plasma gas, He gas, H ₂ gas or the like is used as a secondary gas to form a plasma.
O ₂ particles are placed and sprayed in a state where, for example, 100% is dissolved in the anticorrosion material 1 (see FIG. 2) such as an iron alloy or stainless steel.

[S4: Welding of TiO ₂ to Corrosion-Protected Material] The molten and solidified layer 2 is integrally formed on the corrosion-protected material 1 by solidifying the molten TiO ₂ .

[S5: Adjustment of Plasma Temperature] The plasma current is reduced and the flow rate of the plasma gas is increased so that the temperature of the plasma flow is reduced. At this time, since the temperature induced low is continued supply of n-type TiO ₂ particles, some undissolved in TiO ₂ in a molten state Ti
A semi-molten layer 3 (see FIG. 2) in which O ₂ particles are mixed is formed.

[S6: Supply of n-type TiO ₂ particles]
The supply of the n-type TiO ₂ particles is performed in a state where the temperature of the plasma flow is induced to be low.

[S7: Plasma Spraying] When n-type TiO ₂ particles are supplied while the temperature of the plasma stream is kept low, the n-type TiO ₂ particles are partially dissolved without being completely dissolved. It is sprayed toward the material 1 to be protected as it is.

[0018]: If the TiO ₂ in a molten state and [S8 particulate n-type TiO ₂ of soldering to the anticorrosion material] granular n-type TiO ₂ particles are fed into the sacrificial material first surface in a mixed state, the molten As the TiO _{2 in} the solidified state solidifies, the n-type TiO ₂ particles are welded while their shapes remain, and a particle layer (n-type TiO ₂ particle layer) 4 is formed on the semi-molten layer 3.

As described above, when the n-type TiO ₂ particles are deposited while changing the plasma current and the flow rate of the plasma gas to substantially lower the temperature of the plasma flow, the TiO ₂ film X to be produced becomes as shown in FIG. As shown, it has a tilted structure. That, in the initial spraying, gradually according although the ratio of n-type TiO ₂ particles by melting and solidification of TiO ₂ is lower, semi-molten layer 3, the particle layer (n-type TiO ₂ particle layer) 4 is formed The proportion of the n-type TiO ₂ particles increases, and finally, a particle layer (n-type TiO ₂ particle layer) 4 in which the proportion of the n-type TiO ₂ particle layer is increased is produced.

[Other Embodiments] In the method for producing a corrosion-resistant titanium oxide film according to the present invention, as shown in S9, instead of supplying n-type TiO ₂ particles in S2, n-type T
TiO ₂ particles other than iO ₂ may be supplied so that the melt-solidified layer 2 is interposed.

[0021]

[Sample A]

Plasma current 400A, plasma gas flow rate 60 liters / min [Sample B] Plasma current 600A, plasma gas flow rate 50 liters / minute, and plasma current 400A, plasma gas flow rate 60 liters / minute (Particle layer is formed after formation)

A cross cut was made in each of the samples A and B, and a cellophane tape was stuck thereon to examine the presence or absence of peeling. In Sample A, peeling was observed in about 20% of the area where the cellophane tape was stuck. In Sample B, no peeling was observed at the portion where the cellophane tape was stuck. In addition, observation of the surface condition revealed that both samples A and B had granular Ti
It was recognized that a large amount of O ₂ was attached. From these results, it can be concluded that a method of gradually increasing the particle ratio by spraying while changing the conditions of the plasma flow rate as in Sample B is effective.

[0023]

According to the method for producing the anticorrosion titanium oxide film and the anticorrosion titanium oxide film of the present invention, the following effects can be obtained. (1) By increasing the particle ratio on the surface of the TiO ₂ film, the function as an optical semiconductor can be improved, and the anticorrosion property can be improved. (2) The adhesion of the TiO ₂ film can be enhanced by forming a melt-solidified layer of TiO _{2 on} the surface of the material to be protected and then forming an inclined structure with an increased particle ratio. (3) By continuously using the n-type TiO ₂ particles and changing the film forming conditions, the workability at the time of film forming can be improved.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of a method for producing a corrosion-resistant titanium oxide film according to the present invention.

FIG. 2 is a front sectional view showing one embodiment of a titanium oxide film for corrosion protection according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Corrosion-proof material 2 Melted solidified layer 3 Semi-solid layer 4 Particle layer (n-type TiO ₂ particle layer) X TiO ₂ film

Claims (6)

[Claims] 1. A method of producing a TiO ₂ film (X) having optical semiconductor properties by spraying n-type TiO ₂ particles on a surface of a material to be protected (1) by putting the particles in a plasma flow.
Step of melting the TiO ₂ particles to form a melt-solidified layer (2) on the material to be protected, and forming the particle layer (4) by welding the n-type TiO ₂ particles by lowering the plasma spraying temperature from high to low. And a method for producing a titanium oxide film for anticorrosion. 2. The method for producing a titanium oxide film for anticorrosion according to claim 1, wherein only the n-type TiO ₂ particles are supplied to form both the melt-solidified layer (2) and the particle layer (4). . 3. A TiO ₂ film (X) having optical semiconductor properties formed integrally on the surface of the material to be protected (1), wherein the TiO ₂ particles formed integrally with the material to be protected are melted and solidified. 1. A corrosion-resistant titanium oxide film comprising: a molten solidified layer (2); and a particle layer (4) integrally formed on the substantially molten solidified layer and having an increased n-type TiO ₂ particle ratio. 4. The semi-molten layer (3) having a particle ratio intermediate between the melt-solidified layer (2) and the particle layer (4). Titanium oxide film for corrosion protection. 5. The anticorrosion titanium oxide film according to claim 4, wherein the particle ratio is set continuously. 6. The anticorrosion titanium oxide film according to claim 4, wherein the particle ratio is set stepwise.