JPH0448080A - Rusted weather resistant steel sheet - Google Patents

Abstract

PURPOSE:To obtain an artificially rusted weather resistant steel sheet having more effectively improved corrosion resistance of the rust film by treating a steel sheet with a rusting soln. consisting of pure water, sulfuric acid, nitric acid, an aq. ammonia soln. and Fe2(SO4)3. CONSTITUTION:A steel sheet is treated with a rusting soln. consisting of pure water, sulfuric acid, nitric acid, an aq. ammonia soln. and Fe2(SO4)3.2H2O or further contg. at least one of CuSO4.5H2O and (NH4)2HPO4 as additives to obtain an artificially rusted weather resistant steel sheet. This weather resistant steel sheet is further treated with a sodium silicate soln. as required. The corrosion of the base iron is effectively inhibited, cracks caused in the steel sheet are coated and the weather resistance can be improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention belongs to the field of chemical surface treatment of metallic materials.
Rusting relates to untreated weathering steel.

(Prior art) Low-alloy high-strength steel (hereinafter referred to as weathering steel) containing small amounts of Ou and 0rSP as alloying elements forms a dense stable rust layer with high protection properties on its surface when exposed to the atmosphere. In order to suppress the corrosion reaction by itself, it was used for exploration without applying anti-corrosion methods such as painting under appropriate conditions, but since it takes a long period of 3 to 5 years for a stable rust layer to form, the initial stage of atmospheric corrosion There are problems such as there is a risk that the steel may flow out during the process and contaminate the WIFM, and that the environment in which it can be used may be restricted because the formation of steel is greatly affected by environmental conditions. Therefore, there is a need for weather-resistant steel in which a stable rust layer is quickly formed on the surface.

Therefore, the applicant of the present application previously secured a rust layer with an appearance similar to natural rust by using a hydrochloric acid-based treatment liquid, but since the rust layer formed by the hydrochloric acid-based treatment liquid contains at-ions, it cannot be used in a humid atmosphere. This method has the drawback of local destruction of the rust layer and new corrosion.

(Problem to be Solved by the Invention) In view of the above, the problem to be solved by the present invention is to secure a rust layer without using a hydrochloric acid-based treatment solution, thereby suppressing corrosion during exposure to the atmosphere, and The present invention aims to provide weathering steel in which the corrosion resistance of the copper coating is more effectively improved.

(Means for Solving the Problems) The first invention taken by this invention to solve the above problems is to use pure water, sulfuric acid, nitric acid, aqueous ammonia, and Fez (5O
4) Artificial rust coating consisting of a composition of 3 @ 2H2O treated with a treatment solution is a weathering steel plate, and the second invention is a rust coating of the first invention treated with a treatment solution of 0tz804 @ 5H,
2O, (!1H4) 2 The casting made by adding at least one of the additives HPO4 and the artificial rusting made by treating with a treatment liquid are weather-resistant steel plates, and the third invention is based on the second invention. Artificially rusted weathering steel sheets are made by treating them with a sodium silicate solution.

(Function) The product according to the first invention has a small corrosion increase and effectively suppresses the corrosion of the base steel, the second invention is effective in reducing the corrosion increase, and the third invention has a small corrosion increase. It covers cracks that occur in the rust layer and strengthens its weather resistance.

(Example) The test piece used was weather resistant f19XssP.
Mu-0 (OOR-TEEMO), the dimensions are 1.0 x 100
×100-. The test piece was pretreated in the following order: decontamination with acetone, polishing with emery paper, 1F, and degreasing with acetone. As shown in the solution composition column in Attached Table 1, the above pretreated test piece was mixed with 1000 vat of pure water, 4 wal of concentrated sulfuric acid, 12.5 ml of concentrated nitric acid, and 10 ml of concentrated ammonia water.
Le2 (804) 3 m 2H2O Rusting in weathering steel with a composition of 1005 layers is below treatment T & C.
This is simply called processing t&. ] Rust was removed using the following procedure.

(1) Apply the treatment liquid & to the surface of the test piece using a brush, immediately heat it to 70°C to 80°0, and volatilize the excess treatment liquid a. After the surface of the test piece has cooled down, apply it again. , treatment liquid & is applied and heated in the same manner. After performing this operation three times, the test piece was aged for 12 hours in a constant temperature and humidity ring maintained at 88 degrees of 2O6aSili to generate casting.

(2) To deal with rust from the second time onwards, use a brush to remove the floating cast formed in the constant temperature and humidity ring, leaving only the inner layer of rust on the surface, and then repeat the same process as in (1). Perform operations.

(3) Perform the above operation twice a day for 3 days.

Once this process is complete, wash the test piece under running water.
After completely removing the floating rust, dry it.

(4) After the above operations, the back and cut surfaces of the test piece were completely covered with vinyl chloride resin paint, leaving the treated surface intact, and subjected to a corrosion test to evaluate corrosion resistance.

In order to investigate the weather resistance of the test piece treated with the above procedure and the untreated test piece, the test piece was subjected to a 6-month atmospheric exposure test, and the results were shown in Figure 1. For the test piece, the increase in corrosion increases with time and depth for 2 to 3 months after the start of fogging, but after that it reaches a maximum value and decreases to 0. In other words, there is no clear difference between the two for the first 2 months. However, after that, the weight of the treated piece increases less (◎◎This shows that the corrosion of the base steel is suppressed by the rust treatment.In the atmospheric exposure test The fact that the test pieces of Izun showed an initial increase in corrosion indicates that the base metal was actively melted during this period.
This indicates that new rust is forming.

Therefore, it is thought that among test pieces that have been artificially rusted, the smaller the increase in corrosion during this period, the better the corrosion resistance of the test piece.

Next, the increase in corrosion weight was confirmed in the previous basic test, but as shown in Figure 2, the increase in corrosion weight is smaller when treated with treatment Oshima than with a hydrochloric acid solution. The treated material (which varies greatly depending on the addition state of the component elements of the weathering steel λ), so the treatment solution a contains On, which corresponds to the ion form of the elution of O, Or, and P, which are the component elements of the weathering steel. !", O'r", P O4'-wo1!
German A Z) or using a combined solution, the above (1)
) to (4), using treated test pieces, an accelerated corrosion test similar to an atmospheric exposure test (constant temperature accelerated test 2 that can keep the corrosive environment constant and evaluate the amount of corrosion in a short period of time) 1 corrosion weight change was confirmed.

First, Ou2+, Ou2” +〇 r3”, On! ”＋P
Rusting caused by treatment solution a containing O43- confirms the treatment, but as shown in Figure 3, when Oul3 is added alone (indicated by Oul3, Cu28), treatment is performed only with treatment solution a. The increase in corrosion is greater when compared to the case where In addition, Ou2+ and Cr3+ were added simultaneously (Cu13
-Cr50 to 0u28-Cr780 with display 2 also showed a large increase in corrosion weight.

On for this! ” and PO43- combined addition (01
When a solution containing 113-P8~0u28-PI32) was used, the corrosion weight increase was reduced, especially when using a solution containing 0tL13-P8.0u28-PI32 (the amount added is shown in !!1. The same applies below). It can be seen that compound addition by a combination of is effective.
The results of the accelerated corrosion test of the test piece treated with a solution containing 3+ and PO43- at the same time are shown in Figure 4, and in this case, one ion species or two ion species shown in Figure 6 Compared to when an additive solution was used, the difference in corrosion weight increase due to the difference in the composition of the treatment solution was even larger. That is, Cu28-Or! 5o-PI32 and 0u
The combination of 28-Or 780-pB is not effective (5
On-13-0r50-PI32 and On-130r5Q
It can be seen that a combination with a small amount of 0tI2+, such as -pB, is effective. However, 0u13-Cr50-
The combination of PI32 and Ou 13-Or5 Q -pB is also Ou13-PI32 and Ou13 shown in FIG.
-The combination and effect of PI3 are almost the same. Therefore, it is judged that the addition of Cr has almost no effect on inhibiting corrosion.

In addition, as a test piece to confirm the effects of temperature and humidity during treatment, rusting, which is thought to affect corrosion resistance, was treated with a solution in which Oul 3-PI32 was added to treatment solution a. The relationship between the number of n1 treatments and the amount of rust deposited was investigated.

The results are shown in Figure 5, and the rusting of the test piece is clearly determined by the difference (weight increase) between the weight immediately after treatment and the weight after aging for 12 hours at the specified temperature and humidity, based on the average of 6 treatments. and others?
As shown in the figure, the humidity is high (the increase in weight is large, and therefore the copper film is also thought to be thicker accordingly. From this, a temperature of 650°C is considered to be effective against corrosion).
1. Since 100% humidity is an extremely bad condition, accelerated corrosion tests were conducted on test pieces that had been treated to prevent rusting under the various aging conditions shown in Figure 5, and as shown in Figure 6. However, the higher the humidity during ripening (in other words, when a thick film is formed), the less the corrosion increases. It is said that corrosion can be suppressed as much as 135°C1 humidity 80°C.
% aging is effective in inhibiting corrosion.

Next, cracks may occur in the rust layer according to the first and second inventions. The presence of cracks reduces durability and makes it impossible to completely prevent flow casting because moisture easily penetrates into the base metal.

Therefore, a third invention aimed at increasing the stability of the rust layer will be described. This is an artificial rust layer impregnated with sodium silicate, and is a weathering steel plate according to the second invention with floating copper removed and with floating rust.
z 35-38≦, H&2O17-18%, H2O43
A weight change test due to accelerated corrosion and an atmospheric exposure test were conducted on the product coated with the solution of ~43 and dried, and a weight change test due to accelerated corrosion and an atmospheric exposure test were conducted on the product that was immersed in the same solution instead of coating and dried. did. the result,
The latter solution showed better results.

In addition, weathering steel can be immersed in the above sulfuric acid treatment solution to
As a result of investigating changes over time, it was found that sulfuric acid-based treatment solutions that had deteriorated due to repeated use could be reused by adding acid to adjust the pH.

(Effects of the Invention) As described above, rusting in the weathering steel according to the present invention is reduced by using the treatment solution.1 (1) Corrosion of the weathering steel when exposed to the atmosphere is suppressed at an early stage. (3) The rusting is caused by On2+, P O4' to the treatment solution.
The combined addition of - is effective in improving the corrosion resistance of copper coatings, especially 15 ppwr On”+ and 132 pPII PO4
The combined addition of '- is effective, (4) Incidentally, if the humidity during treatment is increased for rusting, the corrosive effect of the treatment solution will be much greater for rusting, and (5) Sodium silicate. By immersing it in a solution, it exhibits characteristics such as improving weather resistance without impairing the texture of rust.

[Brief explanation of drawings]

Figure 1 is a diagram of corrosion weight change in atmospheric exposure test of a test piece treated with treatment liquid a according to the present invention for rusting and an untreated test piece.Figure SN2 is a graph of rusting treated with treatment liquid a and a hydrochloric acid solution. Figure 3 shows a diagram of weight change in accelerated corrosion test of test piece (350% humidity 100 times).
Accelerated corrosion test (350S) of test pieces treated with a solution containing S (On2Z PO45-)
Fig. 4 is a weight change diagram at ffi degrees 100≦].
Accelerated corrosion test (3
Weight change diagram at 5°01 humidity 100%2, Figure 5 shows rusting due to treatment liquid, aging conditions during treatment (weight change of test piece when changing temperature and humidity Figure 1 Figure 6) Rusting due to treatment solution a is a graph of changes in corrosion weight in an accelerated corrosion test (65 os humidity 100%) when the aging conditions during treatment are changed.Table 1 shows the composition of the rusting treatment fia and additive solution. It is something.

Claims (3)

[Claims] (1) Pure water, sulfuric acid, nitric acid, ammonia water, and Fe_2 (
A rust-resistant weathering steel plate treated with a rust treatment solution having the composition SO_4)_3.2H_2O. (2) Pure water, sulfuric acid, nitric acid, ammonia water, and Fe_2 (
SO_4)_3・2H_2O composition solution CuSO
A rust-resistant weathering steel plate treated with a rust treatment solution containing at least one of the following additives: _4.5H_2O and (NH_4)_2HPO_4. (3) Pure water, sulfuric acid, nitric acid, aqueous ammonia, and Fe_2 (
SO_4)_3・2H_2O composition solution CuSO
A rust-proof weathering steel sheet that is treated with a rust treatment solution containing at least one of the following additives: _4.5H_2O and (NH_4)_2HPO_4, and then treated with a sodium silicate solution.