US3616342A

US3616342A - Process for the removal of metal powder and low metal oxides from the surfaces of bundles of wire which have been etched with sodium hydride

Info

Publication number: US3616342A
Application number: US690717A
Authority: US
Inventors: Arnold Lenz; Walter Rogler
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1966-12-10
Filing date: 1967-12-11
Publication date: 1971-10-26
Anticipated expiration: 1988-10-26
Also published as: NL6716716A; GB1203980A; JPS5121938B1; DE1496785A1; SE394896B; BE707727A

Abstract

Improvement in the known process for removing rust or scale from metal objects, especially wires, by immersion of the object in caustic soda, caustic potash, or a mixture thereof, followed by inducing an electric current to pass therethrough while maintaining the object in an alkaline medium which improvement involves using lye of at least 60 percent concentration as the alkaline bath and operating at up to about 25* C. over the solidification point of the alkaline bath.

Description

O United States Patent [1113,616,342

[72] Inventors Arnold Lenz [56] References Cited Q Z Q M H h f UNITED STATES PATENTS 1,600,355 9/1926 Otis et a1 204/145 A 1 No 690 2,377,876 6/1945 Gilbert 204/145 X 2,468,006 4/1949 Webster 204/145 [22] Med 1967 2 847 374 8/1958 Webster eta] 204/145 [45] Patented Oct. 26, 1971 [73] Assignee Dynamit Nobel Aktiengesellschaft FOREIGN PATENTS Troisdorf, Germany 502,176 4/1951 Belgium 204/145 [32] Priority Dec. 10, 1966 155,712 10/1961 U.S.S.R. 204/145 [33] Germany Prim E xammer---Damel E. Wyman D 51 750 Asrislan! Examiner-P. E. Konopka Attorney-Burgess, Dinklage & Sprung [54] PROCESS FOR THE REMOVAL OF METAL POWDER AND LOW METAL OXIDES FROM THE SURFACES 0F BUNDLES 0F WIRE WHICH HAVE ABSTRACT: Improvement in the known process for remov- BEEN ETCIIED WITH SODIUM HYDRIDE t l f t l ts u b 7 Claims 1 Drawing g mg rus or sea e rom me a o ec especra y wires, y 1mmerslon of the ob ect 1n caustic soda, caustic potash, or a mix- [52] US. Cl 204/141, ture thereof, followed by inducing an electric current to pass 204/145 R, 204/145 F therethrough while maintaining the object in an alkaline medi- [51] Int. Cl Cl0b 1/06 um which improvement involves using lye of at least 60 per- [50] Field of Search 204/1451, cent concentration as the alkaline bath and operating at up to I45, 141, 140 about 25C. over the solidification point of the alkaline bath.

PATENTEDum 26 I97! AUXILIARY CATHODE um My HooE m M 3% w 9 www Wmu w IRA 0.

ATTORNEYS.

PROCESS FOR THE REMOVAL OF METAL POWDER AND LOW METAL OXIDES FROM THE SURFACES OF BUNDLES OF WIRE WHICH HAVE BEEN ETCHED WITH SODIUM HYDRIDE This invention is directed to the cleaning of metals. It is more specifically related to the removal of rust and/or scale from wire coils.

Processes are known for reducing rust or scale on metal surfaces by immersing the metal objects in a bath consisting of molten caustic soda and/or caustic potash plus sodium hydride in a quantity of 0.5 to 3 percent of the weight of the caustic soda and/or caustic potash, and then removing the reduced coating from the metal surface by electrical treatment in an alkaline medium. The electrical treatment involves passing a current through the object, first using the object as an anode, and then by polarity reversal, using the object as a cathode. ln the case of bundles of wire, particularly a coil, it is difiicult to remove the rust or scale from the interior of the bundle. Complete removal of the rust or scale is achieved only on the outer surface of the bundle. This is probably due to the fact that the current lines run only in the outer surface of the bundle.

It is an object of this invention to provide an improved process for removal of rust and/or scale from a metal object, particularly a wire coil.

Other and additional objects of this invention will become apparent from a consideration of this entire specification including the claims and the drawing hereof.

ln accord with and fulfilling these objects, one aspect of this invention resides in a process for the removal of rust and/or scale from the surface of a bundle of wire which process comprises etching the bundle of wire in molten caustic soda or molten caustic potash containing sodium hydride; and then passing an electric current through the bundle of wire while such wire is immersed in an alkaline medium having a lye content of at least about 60 percent. The alkaline bath is maintained at up to about 25 C., preferably about to 20 C., above its solidification point. During the electrical treatment the polarity of the current is reversed so that for part of the treatment the wire bundle is the anode and for part it is the cathode.

Surprisingly it has been found that the rust or scale can be completely removed, even in the interior of the wire bundle, if the temperature and concentration conditions of the invention are sustained in the lye bath. The metal compounds developing from the metal powder and the low metal oxides in the post-treatment settle out and are captured at the bottom of the lye bath in separate containers. This process may be carried out with agitation or in a quiescent state. ln steady operation the bath has an average iron content of approximately 0.1% Fe O ln the anodic and cathodic process the current passes through the suspended wire bundle, the lye bath and, as the counterelectrode, a plate made of corrosion-resistant steel s1 spended in the lye bath. The anodic treatment is completed as soon as a yellowish violet coating has formed in the interior of the bundle.

The process of this invention can be improved if an additional cathode is inserted through the center of the suspended wire bundle. ln the cathodic treatment that follows, and which is accomplished merely by reversing polarity while the arrangement remains the same, the yellowish violet coating is dissolved and is also chipped ofi by the cathodic evolution of hydrogen, so that the wire surface becomes metallically clean. Since the course of the current lines is disturbed at the point where the wire bundle contacts its hanger, and for this reason the anodic and cathodic etching does not take place to the desired extent at this point, it is desirable to change the position of the bundle on the hanger after half of the anodic etching time and half of the cathodic etching time have passed, so that the previous points of contact or hearing points become freely accessible to the flow of current.

This invention will be better understood by reference to the accompanying drawing, the single figure of which is a schematic side elevation of the arrangement of parts in the lye bath during anodic and cathodic treatment.

The following examples are illustrative of this invention without being limiting on the scope thereof.

Example 1 A -kilogram wire bundle having an inside diameter of 400 to 500 mm., a wire diameter of 3 mm., and a scale content of 0.3 percent, is immersed, after hydride etching, into a lye bath containing 60% NaOH/KOH. The bath temperature is 70 C. The bundle is treated anodically for 20 minutes at a current of 1,500 amperes. A violet coating forms in the core of the bundle. In the cathodic treatment then following, which is also performed for 20 minutes at 1,500 amperes, the coating that developed in the anodic treatment comes of? completely.

At the middle of the anodic treatment and at the middle of the cathodic treatment, the point of contact between the wire bundle and its hanger is changed by turning the wire bundle. Finally the wire is rinsed in cold water and protected against further corrosion by immersion in a lime bath.

The same procedure is followed in all the further examples set forth below.

Example 2 A wire bundle of the same kind as in example I is treated anodically and cathodically at 65 C. in a 60 percent caustic soda lye after the hydride etching. With a current of 1,500 amperes, the black coating on the metal is transformed within 20 minutes into a yellowish violet compound extending all the way into the core of the bundle. A cathodic treatment at 1,500 amperes for 20 minutes is required for complete cleaning. Then the bundle is rinsed in cold water and dipped in milk of lime.

Example 3 A wire bundle as in examples 1 and 2 is immersed, after hydride etching, into 60% KOH at a temperature of 75C.

In the anodic post-treatment at 1,500 amperes, a yellowish violet coating forms within 20 minutes, which is completely removed within 20 minutes by reversing the polarity.

The wire bundle is then rinsed with water and protected against further rusting with lime.

Example 4 A wire bundle of the same kind as in examples l to 3 is immersed after hydride etching into a bath of molten 100% NaOh/KOH at 215 C.

The anodic treatment is performed at 1,500 amperes for 5 minutes. The yellowish violet coating that forms is not resistant and largely redissolves. What is left is an extremely thin yellowish coating which is entirely removed by the reversal of polarity (5 min. at 1,500 amp.).

The bundle is washed in cold water and then dipped in milk of lime.

Example 5 A wire bundle as in examples 1 to 4 is immersed in a bath of molten 100% NaOH at a temperature of 330 C.

After 5 minutes of anodic treatment at 1,500 amperes, the bundle turns golden yellow all the way into the core.

The bundle is then washed in cold water and dipped in milk of lime.

Example 6 A bundle of wire as in examples l to 5 is immersed into a bath of 100 percent molten KOH at 370 C. After 5 minutes of anodic post-treatment at 1,500 amperes the bundle has assumed a yellowish color extending all the way into the core. For cathodic cleaning, 5 minutes are required. The bundle is washed in cold water to remove all the alkali and is then dipped in milk of lime.

The electric current intensities stated in all examples can be reduced down to about 1,000 amperes, although longer cleaning periods will then be necessary.

What is claimed is:

l. in the process for removing scale and rust from metal thereof. wire bundles by etching such in molten caustic "comprising 3. The improved process claimed in claim 1 wherein said sodium hydride and at least one member selected from the bath isabout 60% KOH/NaOi-l and isat about 70C. group consisting of caustic soda and caustic potash and then 4. The improved process claimed in claim 1 wherein said subjecting such to electric treatment with a current of at least 5 bath 9" 50% and 15 abofll I about 1,000 amperes" has been inserted in a liquid alkaline T Improved P l 1 when!" Bald bath both as an anode and as a cathode; the improvement bath"; abQut 60% and is 75 which comprises providing said alkaline bath as at least about T lmpmved Process clfnmed 1 wherein 60 percent lye and at a temperature up to about 25 C. above 533115 9 /K H and mat about 2 l5 C. l the solidification poimthereofi l0 7. The improved process claimed in claim 1 wherein said 2. The improved process claimed in claim 1 wherein said bath 100% a! abou 330 liquid bath is about l0 to C. above the solidification point

Claims

2. The improved process claimed in claim 1 wherein said liquid bath is about 10 to 20* C. above the solidification point thereof.
3. The improved process claimed in claim 1 wherein said bath is about 60% KOH/NaOH and is at about 70* C.
4. The improved process claimed in claim 1 wherein said bath is about 60% NaOH and is at about 65* C.
5. The improved process claimed in claim 1 wherein said bath is about 60% KOH and is at about 75* C.
6. The improved process claimed in claim 1 wherein said bath is 100% NaOH/KOH and is at about 215* C.
7. The improved process claimed in claim 1 wherein said bath is 100% NaOH and is at about 330* C.