JPS5950182A - Removing method of al melt-sprayed film - Google Patents

Abstract

PURPOSE:To improve efficiency and safety and to enable the removal of an Al melt-sprayed film at a low cost by performing said removal by a chemical treatment in place of mechanical grinding. CONSTITUTION:An aq. NaOH soln. is coated on an Al melt-sprayed steel plate and is brought into reaction with Al to form sodium aluminate in the case of removing only the Al melt sprayed film in the specified range near the weld line of said steel plate. The Al melt-sprayed film which is hardly strippable is converted to the above-described Al compd. which is easily strippable, then said compd. can be removed by, for example, washing. However, the aq. NaOH soln. when coated in this case spreads to the outside of the specified range. Thereupon, the aq. NaOH soln. incorporated with 0.5-3.0wt% alpha-starch to have viscosity is coated thereon. Such aq. soln. flows after coating and the coated range expands slightly but the flowing range is uniform and can be predicted and limited with respect to a specified coated amt., because the liquid surface dries to hardness and the liquid is internally agitated by foaming, by which the reaction with the Al is effectively accelerated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an AAiWAt thermal spray coating method that can remove A2 solvent coatings efficiently and at low cost.

At solvent plating on steel plates has excellent anti-corrosion properties and is therefore often used for anti-corrosion of large copper plate structures such as tanks.

Corrosion protection by At spraying on tanks, etc. has traditionally been carried out on-site by workers manually spraying At on tanks, etc. after assembly has been completed, but recently, IiQ Ironworks has Efficient production of high-quality At sprayed steel sheets in-house has become possible, and this A2 Yukawa 1i1
Since the method of using plates has been superior in quality and productivity, it has become popular as a first step in corrosion protection for tanks, etc.

The above-mentioned A7 solvent steel sheets are mainly assembled into tanks, etc. at construction sites using a single bath. However, since welding with a welding method that leaves the At thermal spray coating remains, welding defects are likely to occur. The film must be removed. In addition, in magnetic particle flaw detection, which is carried out in a prescribed inspection at the beginning of use of tanks, etc., the ability to detect defects from above the At sprayed coating is poor when there is no At sprayed coating ((in comparison, it is inferior).
It is necessary to remove the At sprayed coating in advance at the locations where magnetic particle testing is to be performed.

Conventionally, grinding with a grinder has been used to remove the A7 molten skin) Iψ, but this grinding with a grinder has the following drawbacks.

■ If the grinder's abrasive grains are too fine, it will cause clogging, making it impossible to continue using the grinder. When the grinding wheel tl'f is made coarser, the grinding reaches to the base steel plate under the At molten coating, and the ground surface becomes rough at A7. As a result, the range of appropriate grinding conditions is narrowed and there is a problem in terms of efficiency.

■ 0 (Dust generated by scraping is significant, the working environment deteriorates, and there are health and safety problems.) The present invention was developed to solve the above problems, and
By performing a chemical treatment to convert the A7 solvent skin 11'A in a specific range to be removed into a compound that is easy to peel off, At can be removed with high efficiency, safety, and low cost. The purpose of this invention is to provide a method for removing thermal spray skin.

As a result of repeated research on the development of a method for removing the At thermal spray coating in the above-mentioned specific range, the inventors of the present invention have found that the method for removing the A7 thermal spray coating by visual grinding using a grinder is as follows:
Instead, the chemical treatment was used to remove A, / = sprayed coating 1 (
It is clear that by changing the compound to a compound that is easy to remove and then chemically removing it by washing with water, it is possible to remove the A7 melting film with high efficiency and safety, and at a low cost. Ra〃 became 1.

That is, since the AJ-bath η, 1 film is a raw T & pregnant skin 11 in which A5 particles are tightly bonded to the steel sheet substrate, basically (r!, an aqueous solution of an alkali, such as NaOH4, is applied to the At film. NaOH and Al are reacted to form aluminic acid)') Lamb (, NaAt, 0.24 nH120
) f generation formula, strip 1ift l-;J Eel;'z
A/It is easily possible to change the molten metal coating %i [L to a 10 aluminum compound.

However, when attempting to remove only the Al sprayed coating in a specific area such as near the weld line mentioned above, the entire thickness of the A7 coating within the above range is sufficient to react with At and produce sodium aluminate. When a large amount of the Na.OH aqueous solution is applied, the NaOH aqueous solution spreads outside the above-mentioned specific range, and even the excess At sprayed coating is removed, resulting in a problem of quality deterioration. Therefore, if it were possible to prevent the spread of the NaOH aqueous solution by some method and keep it within the specified range, the above-mentioned disadvantages could be eliminated.

As methods for preventing the NaOH aqueous solution from spreading, there are two methods: a physical method of preventing the spread by building a barrier around the periphery of the specific range, and a chemical method of preventing the spread by applying viscosity to the solution itself. I can't help but think about it. Since the physical method of i'+i1 is economically additional, the latter chemical method was further investigated. As a result, the flow range of the solution in N0101 [nIJ can be regulated by adding a binder to the aqueous solution to give it an appropriate viscosity, and the spread of the solution in the specified range (2) is prevented in 9. It turns out that this is possible on the first day of the month.

That is, for example, a solution containing an appropriate amount of α-powder in a NaOH aqueous solution of an appropriate concentration has the ability to maintain an appropriate viscosity without impairing the chemical activity of NaOH. When the above solution is applied to the At thermal spray coating, the solution flows after application and the application range expands slightly, but the flow range is uniform and the flow 1161 area should be predicted and limited for a certain amount of coating. Since it is possible on "Tuesday", regulating the flow range becomes 1+iJ ability. This is a temple where the surface of the liquid dries and becomes hard; inside it,
Since the liquid is completely stirred by foaming due to the reaction between Na0I-I and AA, the reaction with A4 in the entire liquid mη,j skin 1tlNj is effectively promoted, and short 11. During lj, aluminic acid tllram production is promoted.

In this way, the sodium aluminate produced by changing the AL in the Af inertia film can be removed by peeling off.
Because of its easy-to-clean properties, it can be easily removed by washing with high-pressure water or by soft polishing with a scourer, eliminating the need for the powerful 43+, q mechanical grinding of conventional grinders, and eliminating the above-mentioned efficiency reduction and safety and health problems. Resolved 1! +ru.

The present invention has been made based on the above knowledge, and its gist is that α ore powder has a weight ratio of 0.5 to 3.0.
At bath spray coating I! which is characterized by applying an aqueous alkaline solution containing 0.9% viscosity to the At thermal spray coating and converting the At into an aluminate that is easy to remove. It is in the method of removing mulberry.

In the method of the present invention, an aqueous solution of caustic soda (NaOH) is typical as the alkaline aqueous solution that reacts with At in the At fused skin 11ψ to produce an aluminate that is easy to peel off. Similar aluminates that are easy to peel can also be obtained using aqueous solutions of ammonia (NH3), hydration power/L/sium (ca(OH,)2), potassium hydroxide (KOH), and the like.

The concentration of the aqueous alkali solution cannot be uniformly defined because the activity varies depending on the type of alkali, but for example, in the case of NaOH, it is preferable to set the concentration to 7 degrees of water solubility with a content of 25% or more.

In the method of the present invention, α1 and flour are used as agents for imparting viscosity to alkaline water, and the reason why the content thereof is limited to the above-mentioned values will be explained below.

When added to an alkaline aqueous solution in the amount of α, the alkaline aqueous solution can be added without impairing the 11 opacity of the alkali, for example, the reactivity of Al with the alkali aqueous solution, and the active foaming stirring W that occurs during the f'+iJ reaction. Since it is possible to give a suitable viscosity to the material, it is most suitable as a viscosity τ1 imparting agent.

The reason why the content of αIiυ powder was limited to 0.5% to 3.0% (wt%) was because if it was less than 0.5%, the viscosity was too low, and the purpose was to limit the flow of the alkaline aqueous solution after application to within a predetermined range.
It is insufficient. Moreover, if it exceeds 30%, the viscosity becomes excessive and the coating solution solidifies before the reaction between At and the alkali progresses sufficiently after coating, resulting in insufficient aluminate formation. Good peeling of Al-molten η・1 skin 11Qj';<? -! ! It is difficult to do so (1[).

In addition to the α-permeable powder, it is permissible to include iron powder, alloy 11ifl powder, etc., which have a dual action with a viscosity of 1: and do not interfere with foaming IW stirring due to the reaction between the alkaline aqueous solution and A4. do not have.

Next, the effects of the present invention will be explained by implementing IMI VC.

Example 1 A7 bath coating 1 sprayed on a steel plate to a thickness of 250μ
i5j was placed completely horizontally, and from above, a coating solution containing α-powder in various amounts within the non-inventive range was added to a NaOH aqueous solution of varying concentrations. , a circular coating area of 3 Q m = s f was applied to provide a sample material of the present invention example. For comparison purposes, a similar coating solution containing a similar NaOH aqueous solution α (which is outside the range of this powder) was applied to the same Al thermal sprayed coating J1φ as above; A sample material of a comparative example was prepared by coating the coating thickness and coating range.

After applying TiT for 24 hours after application, each test sample in the above two examples was washed with water and scrubbed with a scrubbing brush to remove the reaction products. Peeling of the product 1'iii t・F filli of the quality of the surname, 1
1] The spread and uniformity of the flow of the liquid after the 127th application, and the viscosity of the coating liquid based on the results of a four-person observation of the foaming and stirring caused by the reaction between the liquid and A2 in Imaichi J1. The performance of removing the At-soluble film of the test sample was determined based on the evaluation of excess and deficiency.

] The S4 results are summarized and shown in Table 1.

In Table 1, peeling 1. Vift property evaluation
Peeling is 1jiii good, △ mark is 4 in the range of 10 to 50%.
1 [Shitamono, fl! I defects, X mark indicates 10% peeling.
Anything less than that indicates a defect. The ○ mark (φ) is still on the viscosity evaluation side.
There is some flow in the coating liquid, but the range is uniform and it stays within lQ** slightly beyond the target coating range (30 dragon dollars), and the viscosity is appropriate. There is almost no fluidity, and the reaction has solidified before it has progressed sufficiently, and the viscosity is excessive. This indicates that the viscosity is too low.

As shown in the table, Comparative Example ■ peels off;
] It spread beyond K and was defective. Similar to Comparative Example ``U-■'', the viscosity was too low and was poor. Comparative Example ■(1) The viscosity was too high, and the liquid flowed poorly after application, and the reaction solidified and peeled off without proceeding sufficiently. Comparative Example ■(-1 : The viscosity was extremely excessive, and the applied liquid hardly flowed, and the reaction did not proceed.
Since the magnetic powder content of 11 tons is appropriate and the viscosity is appropriate/h, the spread of the underarm is uniform and within the appropriate range, and the reaction progresses sufficiently to obtain good peelability and can be applied within a specific range. The A2 lytic membrane removal VC column showed good results.

As is clear from the above explanation, the method for removing the All-soluble coating of the present invention involves chemically treating a specific range of the A7 thermal spray coating to convert it into a compound that easily peels off, instead of the conventional direct removal by grinding. It can be removed by simple washing with water, etc., which improves removal efficiency, safety, and reduces costs, reducing corrosion protection costs for buildings using At thermal sprayed steel sheets. It has a remarkable effect on improving the efficiency of 8-year-old plants.

Applicant Sumitomo Metal Industries Co., Ltd. Representative Patent Attorney: Shigemoto H.:
, 5 Voluntary procedure amendment dated October 1982 1. Commissioner of the Japan Patent Office Kazuhiro Wakasugi 1. Indication of the case 1989 Patent Application No. 160600 2. Title of the invention A7. Method for removing thermal spray coating 3. Person making the amendment Relationship to the incident Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (
211) Sumitomo Metal Industries Co., Ltd. Representative nμ Norihiro Tani 4 Agent 6 Subject of amendment Mei, in 7jA column 7 of “Detailed description of the invention”
Contents of the amendment (1) From page 2 of My, line 7 to line 1211 of Book ■, ``It is still the case that the stipulated conditions at the time of the start of use of tanks, etc.''
...The A4 melting layer 1 film must be removed in advance. ”
[Also, in magnetic particle flaw detection performed in inspections of tanks, etc., the ability to detect defects from above the At spray coating is as low as At solvent coating 1.
Depending on the relationship between the At film thickness and the required inspection output, the At bath spray coating may be removed in advance at the location where magnetic particle testing is to be performed, since it is inferior to the case without 1ψ. ”.

Claims (1)

[Claims] (1) Apply an alkaline aqueous solution containing 0.5 to 3.0% by weight of α magnetic powder and give it viscosity to the AA spray coating.
A method for removing an At thermal spray coating, characterized in that T is removed by changing it to an aluminate that is susceptible to peeling.