JPH05320959A - Rust preventing method for electrolytic iron - Google Patents

Abstract

PURPOSE:To obtain an easy method for rust prevention of high-purity electrolytic iron by subjecting pieces of electrolytic iron to wet barrel polishing with a soln. containing nitrite, phosphate, and carbonate, dipping the pieces in a rust preventing liquid containing nitrite and phosphate, and drying. CONSTITUTION:An electrolytic iron is crushed into about 3-100mm pieces and subjected to wet barrel polishing with a soln. containing nitrite (e.g. NaNO3 with 4-8wt.% concn.), phosphate (e.g. Na4P2O7 with 4-8wt.% concn.), and carbonate (e.g. Na2CO3 with 5-9wt.% concn.) and washed with water. Then the pieces are dipped in a rust preventing liquid containing nitrite (about 0.5-1.2g/l concn.) and phosphate (about 0.6-1.3g/l canon.) and dried. By this method, rust prevention is effectively and easily performed for high-purity electrolytic iron.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rust preventive method for high purity electrolytic iron useful as industrial pure iron.

[0002]

2. Description of the Related Art Electrolytic iron is remarkably less in various impurities than ordinary mild steel, and is therefore widely used in fields requiring high quality such as magnetic materials, electronic materials and special alloy materials. Electrolytic iron is usually obtained by electrolyzing soft iron as an anode and stainless steel as a cathode using a hydrochloride or sulfate bath, and electrodepositing high-purity iron on the cathode.

Since electrolytic iron has a high degree of purity, it has the property of protecting the inside if an extremely thin oxide film is formed on the surface. Therefore, if the electrolytic iron obtained by electrodeposition is thoroughly cleaned and stored in a dry atmosphere, rust can be prevented to a considerable extent. In addition, a method of applying oils and fats to the surface of electrolytic iron to prevent rust can be considered, but applying oils and fats is not preferable because it causes impurities such as carbon and oxygen to be mixed in at the use stage.

[0004]

When the surface of the electrolytic iron is smooth, less impurities are attached and rust is less likely to occur. Generally, however, the electrolytic iron surface obtained by electrodeposition has fine protrusions and dents. However, it does not maintain good smoothness. Electrolytic iron with a non-smooth surface is prone to rust from protrusions and dents, and the one obtained using a hydrochloric acid salt bath is particularly prominent, and it is difficult to prevent rusting in ordinary canned storage. Is.

Further, even if the surface is dirty, rust is generated from the contaminated part. Therefore, although the contaminated part is usually polished and removed by dry barrel polishing or the like, the rust cannot be effectively prevented.

[0006]

In the present invention, electrolytic iron is crushed to an appropriate size, wet barrel polished in a liquid in which nitrite, phosphate and carbonate are dissolved and washed with water, and then nitrite and phosphorus are added. A means of drying after immersing in an anticorrosive solution containing an acid salt was adopted. The electrolytic iron to which the present invention is applied may use either a hydrochloride bath or a sulfate bath, but the effect of the former is remarkable. Usually, electrolytic iron is electrodeposited in a plate shape having a thickness of 5 to 10 mm, which is crushed into small pieces of 3 to 100 mm and barrel-polished in a mill. For barrel polishing, a barrel abrasive such as alumina may be used, but it is sufficient to use only the polishing power of electrolytic iron without using any abrasive. When barrel-polishing, wet polishing with an aqueous solution containing nitrite, phosphate and carbonate to clean the surface produced by barrel-polishing and at the same time oxidize the surface to a very thin level for rust prevention To

Sodium nitrite (NaNO ₃ ), potassium nitrite (KNO ₃ ), etc. can be used as the nitrite used for the wet barrel polishing. As the phosphate, sodium pyropolyphosphate (Na ₄ P ₂ O ₇ ), sodium tripolyphosphate (Na ₅ P ₃ O ₁₀ ), sodium tetrapolyphosphate (Na ₆ P ₄ O ₁₃ ) and the like can be used. The carbonates include sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), lithium carbonate (Li ₂ CO ₃ ).
Etc. are available.

These salts are dissolved in water and added to the mill. The concentration of salt is 4-8 wt% for nitrite and 4-for phosphate.
8 wt% and 5 to 9 wt% carbonate are suitable. The amount of the aqueous solution is not particularly limited, as long as the surface of the electrolytic iron is wet during polishing, and depending on the size of the mill, it is about 50% with respect to the charged amount as a guide. The polishing time is 1 to 5 hours depending on the surface condition of electrolytic iron.

After completion of polishing, the product is washed with water to remove polishing powder and salts, and then immersed in a rust preventive solution containing nitrite and phosphate to be dried for rust preventive treatment. As the nitrite and the phosphate used in the rust preventive solution, the same ones as those used in the wet barrel polishing can be used, but the concentration of each salt may be diluted to 1/5 to 1/8. .. That is, the nitrite concentration of the rust preventive solution is 0.
5-1.2 g / l, phosphate concentration 0.6-1.3 g /
l is suitable. Furthermore, 0.5 to 3 g / l of isopropyl alcohol or the like may be added as a surfactant. Thus, by dipping in a solution containing a small amount of salt, an extremely thin anticorrosive film is formed on the surface of electrolytic iron. The immersion time may be several minutes.

[0010]

According to the present invention, electrolytic iron pieces are subjected to wet barrel polishing in an aqueous solution containing nitrite, phosphate and carbonate to remove impurities in the dents adhering to the surface of electrolytic iron by grinding, cleaning, and at the same time. The produced surface is immediately subjected to phosphoric acid film treatment. Furthermore, the treatment for forming an extremely thin rust preventive film is performed by using a more dilute salt solution.

[0011]

[Example] Electrolytic iron having an average thickness of 5 mm produced by using a hydrochloride bath was crushed to 7 to 50 mm, charged into a mill and subjected to wet barrel polishing. Barrel polishing conditions are as follows. Electrolytic iron charging amount: 600 kg Solution charging amount: 300 l Solution component and concentration: Sodium nitrite 6 g / l Sodium phosphate 6 g / l (Na ₄ P ₂ O ₇ , Na ₅ P ₃ O ₁₀ , Na ₆ P ₄ O) ₁₃ ) Sodium carbonate 7g / l Mill rotation speed 30rpm Polishing time 4 hours

After the completion of the wet barrel polishing, the electrolytic iron pieces were thoroughly washed with water, sodium nitrite 0.9 g / l, sodium phosphate 1.05 g / l and isopropyl alcohol 0.9.
It was immersed in an aqueous solution containing g / l and heated to 80 ° C. 1
After soaking for 0 minute, it was taken out and completely dried. Store the rustproof electrolytic iron piece in a sealed can and
Upon inspection after a lapse of months, no rust was found.

For comparison, electrolytic iron of the same lot as that used in the above example was stored in a can sealed without any treatment, except that it was sufficiently washed with water after electrolytic deposition and dried.
After one week, the inspection revealed that rust was found in about 5%. After 3 months, 90% or more of the rusts were found to be rusted.

[0014]

According to the present invention, rust can be effectively prevented by a simple method, and even when used as a raw material for electronic parts, the rust preventive coating on the surface of electrolytic iron does not cause any trouble. ..

Claims (1)

[Claims] 1. An electrolytic iron piece is wet barrel polished with a solution containing nitrite, phosphate and carbonate, and then immersed in an anticorrosive solution containing nitrite and phosphate and then dried. How to prevent corrosion of electrolytic iron.