US1395730A - Rust-preventing process - Google Patents

Description

. It is also DAVID REICHINSTEIN, OF ZURICH, SWITZERIlAND.

RUST-PREVENTING PROCESS.

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No Drawing.

To all whom it may concern:

Be it known that I, Dr. I STEIN, a citizen of the Republic of Switzerland, residing at Zurich, No. 51 Universitriitsstrasse, Switzerland, have invented certain new and useful Improvements in Rust- Preventing Processes; and I do hereby declare the following to be a full, clear and exact descriptionpf the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

It is well known that alkaline solutions, such as NH NaOI-l, act as rust preventers at room temperatures, because it is suppose that they produce an alkaline reaction having a retardin effect upon the formation or oxid.

lmown that iron surfaces can be provided with a rust-preventing coating of iron nitrid by heating the iron artcles in a gaseous atmosphere capable of forming a nitrid. These processes are naturally not suitable for preventing the formation of rust on such iron surfaces, such as the parts of steam turbines, steam boilers, etc., which are exposed to the action of steam containing air at a'high temperature. By the expression iron surface is meant here a surface composed exclusively of iron or only partly of iron, such as for instance a surface of nickel-steel or other iron alloys.

Contrary tothe many existin theories of the formation of rust (see or instance Liebreich East and Rostschuta published by Vieweg & Sohn), the formation of rust can be completely explained if'it is considered to be analogous to the dissolution of a metal in an acid solution containing an oxidizer (see article by Reichinstein in the Zez'tsch, f'iir E lektrochemie 1914 and 1915). According to this view the formation of rust may be represented by the following reactions.

1. Adsorption of the oxidizer for instance atmoslpheric oxygen by the iron surface.

2. ecomposltion of the oxidizer in the adsorption volume of the ironsurface, for

instance, 0 2O 3. Chemical reaction between the constitu ents of the adsorption volume: 2Fe+30+6H 2Fe +3H O.

4. Association of the Fe and OH ions, if their. solubility product is exceeded:

- Fe +30'H Fe(OH) All the reactions therefore take place in Specification of Letters latent.

d 1 c.) the Ferateiitea Nov. 1, 1921.

application filed. December 18, 1916. Serial No. 137,720.

the homogeneous phase of the iron surface adsorption volume). The H and OH ions pass into the adsorption volume from the adjacent liquid phase by prevention. If the iron is in contact with water vapor or steam, the latter is adsorbed partly by the lron surface and becomes dissociated therein:

The passive effect of the oxidizer consists 1n the increase of the O-concent'ration of the adsorption volume, so that according to the displacement principles (Reichinstein and H'- concentration is dimin- 1shed, and this must necessarily lead to a retarding of the velocity of the reaction 3'.

Analogously to that, the poisonous effect consists in the adsorption of poison by the lI'OIl surface which leads to the diminution of the concentrations of all the substances that share in the reaction 3.

The rust-preventing effect of alkali's con-- sists inthe fact that the reaction 3 is slow, and the reactlon 4. is rapid, so that a diminution of the H'-ions-concentration by the alkali has an appreciable efiect upon the I velocity of the formation of rust. This has led the inventor further to the use of volatile'bases, for instance ammonia, of rust-preventlon 1n cases for the purpose where the iron is in contact with-water vapor or steam containing air. j

Experiments. have shown that iron which is exposed toa mixture of air, water vapor and ammonia at 100 C., does not rust at all, whereas without ammonia, rusting begins after barely five minutes.

Example: Ammoniais added to the feed water of the steam boiler of a steam turbine. The

ammonia passes with the steam into the turbine whereby the latter is protected from rust. Y

The ammonia can also be mixed in gaseous form under high pressure with" the steam of the turbine by means ofa'specia' apparatus. Instead of using pure'ammonia, the turbine may be blown through from time; to time with a mixture of nitrogen and ammonia under high pressure. The volatile base may also be produced by introducing a salt of the respective base into the steam boiler, and adding by means of a special apparatus a less volatile base, for instance NaOH, drop by drop into the boiler.

--O ther bases such I as anilin, which are either volatile theml selves orwith steam, may be employed for the same purpose. a I

The process according to the present invention provides a rust-preventing agent in gaseous form, so that the rust-preventing agent will come into contact even with the diificultly accessible parts of the surfaces that are to beprotected.

In order to furnish an indication of the quantity of ammonia it is desirable to employ, it may be stated that, in the case of a 3000 H. P. turbine built for a normal steam pressure of 165 lbs. per square inch and a speed of 3000 revolutions per minute, about 600 kgs. of steam is admitted to the turbine in fifteen minutes, and a solution of ammonia was injected at two points, namely, immediately behind the regulating slide valve, and at the top in front of the last slide ring but two. The ammonia solution had a strength of and the admission took place as follows: during two minutes before the heating up of the turbine, during the heating up, and during the working from 12 noon to 6 p. m. every hour for one minute, then at 6 p. m. for five minutes, during the shutting down of the turbine. The total amount injected was about 40,1iters (these 40 liters contain 80 grs. of NH,).

It-is to be observed that when ammonia or ammonium salts are, in accordance with the present invention, added to boiler waters they are not added in conjunction with or- -treated by av recognized ganicniaterials, graphite and such other substances as are considered to assist in the direction of preventing inrustation, thus when a less volatile base such as sodiuni-hydroxid is, in carrying the present invention into effect, added to the boilerwater, it is added solely in the proportion necessary to set free the more volatile as indicated above.

' It is however to be remarked that from the above explanatorystatementit is not to be inferred'that the water may not have been process.

What I claim is:

1. A process for preventing the rusting of iron surfaces of steam operated apparatus contacted by steam containing air at high temperatures, which comprises adding from time to time a gaseous base mixed with nitrogen to the steam containing air.

2. A process for preventing the rusting of iron surfaces of steam-operated apparatus contacted by steam containing air, which comprisesblowing from time to time through such apparatus with the steam and air mixture ammonia and nitrogen under pressure.

In testimony that I claim the foregoing as my invention, I have signed my name in presence of two subscribing witnesses.

DR. DAVID REICHINSTEIN.

Witnesses-z ARNOLD LEHNER, CARL GREBLEIN.