JPS58160287A - Storage tank for liquid - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to liquid storage tanks, and more particularly to tanks having two innings for storing corrosive solutions.

High corrosion resistance is required for tanks that store various liquids, and in the case of steel tanks, anti-corrosion coatings such as resin linings are applied. is used.

In addition, nine methods have been proposed to improve corrosion resistance by applying the VCWI corrosion protection method. However, when cathodic protection is applied to a steel tank that has been coated with two coats of anti-corrosion coating, if the potential at the cathode becomes lower than the hydrogen generation potential due to excessive corrosion protection, water builds up on the steel surface under the anti-corrosion lining coating. There is a risk that corrosion may occur due to the koji produced by the blistering of the paint.

On the other hand, stainless steel has a potential range where stress corrosion cracking occurs in various droplets (Reference, Japan Iron and Steel Institute; Stress corrosion cracking of steel Ws5B-5), so stainless steel tanks and piping should be protected against cathodic corrosion. It is difficult to select the potential for this purpose.

In addition, when using the galvanic anode method for cathodic protection, if the corrosion protection potential exceeds the required level, the galvanic anode and (sacrificial anode) are consumed rapidly, and the number of sacrificial anodes must be increased or the anode replaced. It was necessary to do this many times, which was very time-consuming.

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to improve corrosion protection in a metal liquid storage tank with a lining that employs a galvanic anode corrosion prevention method, and to reduce wasteful consumption of sacrificial anodes. It depends on preventing.

Generally, in order to electrolytically protect a metal body under corrosion product conditions, it is necessary to polarize the potential of a local cathode portion on the surface of the metal body to the potential of one local anode portion.

For example, in seawater, this state is said to occur if the potential is α2 to 0.3 μ lower than the steady potential shown in the natural potential series of the metal to be protected. The corrosion protection potential of steel in seawater is approximately -α8■ on a saturated amber basis.

On the other hand, Table 1 shows stress corrosion cracking of stainless steel in various solutions. ! 5K, 20%NJiCj+1%N"tCro4 solution -1'8 U 8304. SUI!131g together-
(Te is said to occur near L36V.

Therefore, the anticorrosion method for liquid storage tanks made of anticorrosive lining and stainless steel requires a range of anticorrosion potential that can prevent both the occurrence of stress corrosion cracking in stainless steel and hydrogen generation on the surface of carbon steel due to excessive corrosion protection. It has been found that constant maintenance is an effective corrosion prevention method.

Therefore, Yusha Honji and others conducted various experiments to confirm this idea. Measure the potential of carbon steel, 8U8304 and 8U8316L, in a test solution containing the components shown in Table 1782. Next, as a sacrificial anode, υ was used, and the potential when combined with carbon steel and 8U83G4w8US31@L was set as a side chamber. The results are shown in Figure 1. From the figure 8US3
The natural potential of 04.8 US31@L and carbon steel is the potential without cathodic protection, and when cathodic protection is applied, each sample exceeds the hydrogen generation potential at around -1.1V KTo. It was installed between the t-wall and the sacrificial anode. A variable resistor was used as the potential adjuster used in this experiment. The potential was set to be less base than the natural potential of carbon steel, but more noble than the hydrogen generation potential, and kept constant for one month. As a result, no corrosion of the carbon steel or stress cracking of the stainless steel was observed, indicating that the steel was sound.

Table 2 The present invention has been made based on the above findings, and includes providing a sacrificial P# electrode in a metal liquid tank having a lining, and maintaining an appropriate anti-corrosion potential between the sacrificial electrode and the tank. An embodiment of the present invention will be explained below with reference to Fig. t-J12.

Figure 2 is a schematic A1 diagram of a liquid storage tank made of carbon steel coated with two coats of anti-corrosion coating and equipped with stainless steel internal piping. In the figure, a carbon steel tank 1 is coated with a resin coating 2 to prevent corrosion, and a stainless steel pipe 3 for flowing hot water, etc. is set inside the tank. The sacrificial anode 4 for applying the electrolytic protection method using the galvanic anode method is connected to the carbon copper 1 and It is electrically connected to stainless steel 3. Corrosive melt 11 [7
is heated with hot water and kept at 50UK at all times.

The ammeter 6Fi is a companion for monitoring the anti-corrosion effect. That is, the sacrificial S electrode 4 exerts a galvanic anode effect and supplies a cathode electrode 1 (anticorrosion current) to each sample through the liquid, but if a current needle 6 for passing this anticorrosion current is installed in the circuit above, The corrosion prevention effect of the current electrolytic anode method can be monitored by measuring the amount of sacrificial anode consumption. There is no problem in using the ammeter 6 all the time for monitoring, or even setting it at the beginning and monitoring from time to time.

In the apparatus of the above embodiment, the corrosion of the stainless steel 1 and the stainless copper 3 could be prevented, and the amount of consumption of the Reishiyou & 4 could be suppressed to the necessary minimum.

Furthermore, it was able to provide more complete corrosion protection than conventional cathodic protection methods. t+, no peeling of the lining occurred.

According to the present invention as described above, a metal liquid storage tank having excellent *proof properties is provided. It also extends the life of the tank. Furthermore, tampering with the sacrificial anode can be avoided, and maintenance of the tank can be facilitated.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the test results of the sacrificial anode, and FIG. 2 is a schematic cross-sectional view of a metal liquid storage tank with a lining. l... Longitudinal steel tank, 2... Resin lining, 3
... Stainless steel piping, 4... Sacrificial anode, 5... Potential regulator, No. 42 IEII ``Nikutou'' Seven Keyaki Electric Power Co., Ltd.〈7〕

Claims (1)

[Claims] 1.1) A sacrificial anode is provided in a metal liquid storage tank having an inning, and a potential regulator is interposed between the sacrificial anode and the tank to maintain an appropriate anti-corrosion potential. liquid storage tank. 2. The scope of the patent claim is that a current needle is interposed between the sacrificial anode, the tank, and the O connection in series with the potential regulator. 8. The liquid storage tank according to item 1. 3. Claim 18, wherein the potential regulator is a variable resistor.
Liquid storage tank according to item 1 or item #12.