US 3025184 A
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Description (OCR text may contain errors)
March 13, 1962 E. R. BLAIR ET AL 7 3,025,184
METHOD OF INHIBITING CORROSION Filed Jan. 51, 1958 /A////5/T/A/6 METAL su Poer //V///B/77N6 META L SURF/46E 70 BE PROTECTED JUPPOET EOLL ape/Am;
FUL (RUM I NVENTORS E/IPL R BAA/P PAUL lMf/APDY BY Q Q M A TTOE/VEKS 3,025,184 METHOD OF'EJH'IBIG CURRQSIUN Earl R. Blair-,Oaklarkyand Paul W. Hardy, Barrington, lillL, assignors to American Can (Iompany, New York, N.Y., a corporation of New Jersey Filed Jan. 31, 1958, Ser. No. 712,298 3 Claims. (Cl. 117-131) The present invention relates to a method of inhibiting atmospheric corrosion or rusting of black iron. More particularly, this invention relates to a method of depositing a trace amount of a particular metal onto the surface of black iron in order to inhibit rusting of the black iron.
Low carbon sheet steel, known in the art as black iron or black plate, is readily susceptible to atmospheric oxidation, commonly known as rusting. For many end uses of black iron, there is a considerable lapse of time between its fabrication by the steel mills and its receipt and use by the end user. During at least a portion of this time lapse, the black iron is subjected to conditions conductive to the formation of rust (high relative humidity and temperature) on its surface.
For many operations, this rust must be removed before the black plate is suitable for the operation intended. Such rust removal requires time and equipment which obviously add expense to the operation.
It is, therefore, an object of the present invention to provide a method for treating the surface of black plate during or after its fabrication at the steel mills which will inhibit rusting of the plate at least until its end use.
Yet another object is to provide a method of the character described which is quick and easy to effect, inexpensive and requires simple, inexpensive equipment.
Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description which is of a preferred embodiment thereof.
Referring to the drawing, the single FIGURE in the drawing is a prospective view of one form of apparatus useful in carrying out the instant invention.
The present invention is based upon the discovery that a thin, invisible deposit of tin or lead on the surface of black plate will effectively inhibit atmospheric oxidation, or rusting, of the black plate surface. This phenomenon was first discovered with tin or lead electrolytically deposited from solution onto the surface of black iron. However, such a procedure for obtaining the desired result was deemed impracticable since it required extensive electrochemical equipment such as liquid holding tanks, electric current supply, drying apparatus, etc. Upon further investigation of this phenomenon, we discovered that the same desired results could be achieved merely by rubbing a solid element of tin or lead onto the black iron surface to be protected.
By means of this discovery, effective corrosion protection of black iron may be accomplished very simply during a steel rolling operation as performed in a steel mill during the fabrication of black plate. To perform this operation, a solid element of tin or lead is mounted at a convenient place in the path of travel of the sheet steel during the rolling thereof so that the sheet steel rubs against this element whereby the corrosion inhibiting metal is abraded onto or applied to the steel surface. Since, as indicated previously, it is necessary merely to a'orade inhibiting metal against the steel surface, no special provision for heating the inhibiting metal or steel surface is necessary. Thus, the abrading operation will take place at any temperature substantially below the melting point of the inhibiting metal, tin or lead, preferably at room temperature. The element may take the form of a stationary bar or block, or of a fixedly mounted roller or cylinder adapted to rotate at a velocity, i.e. di-
rection and/or speed, different from that of the moving steel sheet.
Tobe effective, the entire black iron surface must be rubbed with the corrosion inhibiting metal. The amount of inhibiting metal deposited onto the surface to be protected is so small as to be invisible. At any rate, the quantity of inhibiting metal amounts to not more than 1X10 lbs. per square inch of surface treated.
It is not known whether or not the inhibiting metal is uniformly and continuously applied over the black iron surface. Because of the almost infinitesimal amount of inhibiting metal applied to the surface, no adequate tests for such uniformity and continuity have been found. However, by virtue of its mode of application, i.e. merely rubbing the inhibiting metal over the surface to be treated, it is believed that the deposit of inhibiting metal is not uniform or continuous since no special precautions or conditions were followed to achieve this result.
The inhibiting metal must be free of oxide. Experiments have shown that rubbing a black plate surface with inhibiting metal having an oxide film thereon produces no corrosion inhibition. However, it is obvious that initially the solid element of inhibiting metal may have an oxide coating thereon which is abraded off or removed after a short period of rubbing contact with the black iron surface; whereupon pure inhibiting metal will thereafter be deposited on the surface to be protected.
Surprisingly, only tin and lead were found to have a corrosion inhibiting effect when applied in accordance with the instant invention. Other metals which are known to form a protective coating on steel were tried and had no corrosion inhibiting effect whatsoever. Among the other metals tried and found ineffective were antimony, aluminum, nickel and titanium. The reason for this difference in action between the efiective inhibiting metals and the non-effective metals is not understood. Although not wishing to be bound by any particular theory, the closest explanation is that the particular electronic configuration of the atoms of tin and lead in relation to steel causes these metals to be effective corrosion inhibitors; whereas the other, non-effective metals have a different electronic configuration causing them to be non-operable.
It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the steps of the method described and their order of accomplishment without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the method hereinbefore described being merely a preferred embodiment thereof.
1. A method of treating a black iron surface to inhibit rusting thereof comprising, passing said surface along a predetermined path of travel, placing a solid element of a substantially pure inhibiting metal selected from the group consisting of tin and lead in said path of travel, and abrading said surface against said element at a temperature substantially below the melting point of said inhibiting metal during the travel of said surface to provide said surface with a thin invisible deposit of said inhibiting metal in an amount of up to 1x10 lbs. per square inch of said surface.
2. A method of continuously treating the surface of a. fiat sheet of black iron to inhibit rusting thereof comprising, passing said sheet continuously along a predetermined path of travel, placing a solid element of a substantially pure inhibiting metal selected from the group consisting of tin and lead along said path of travel, and abrading said surface against said element at a temperature substantially below the melting point of said inhibiting metal during the travel of said sheet to provide said surface with a thin invisible deposit of said inhibiting metal in an amount of up to 1x10 lbs. per square inch of said surface.
3. The method set forth in claim 2 wherein said solid element of inhibiting metal is fixedly positioned along said path of travel.
References Cited in the file of this patent UNITED STATES PATENTS