US2414768A - Slushing compound and method for protecting metallic surfaces - Google Patents

Description

Patented Jan. 21, 194'.

SLUSHING COMPOUND AND METHOD FOR PROTECTING METALLIC SURFACES Theodore'G. Roehner, Malverne, and Louis H.

Sudholz, Flushing, N. Y., assignors to Socony- Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application August 12, 1942, Serial No. 454,574

4 Claims. (Cl. 252-33) This invention relates to a composition of the type known as slushing compounds for protecting metallic surfaces from corrosion by the application thereto of a film capable of inhibiting such corrosion.

Many compositions of matter have been used for the protection of metals from corrosion, the

latter being caused in most common cases by a combined action of moisture and oxygen, although in specific cases various other corrosive agents, such as acids, salt solutions, etc., are important factors.

The function of the slushing compound is to form a protective film on the surface of the metal sufiiciently resistant to the prevailing temperature and the action of the various aforementioned agents. Depending upon the severity of service, a wide variety of products has been used beginning with straight mineral oils, fats and blends thereof, petrolatums with or without neutralizing agents, polar compounds and the like.

We have discovered that nitrated fats, such as nitrated tallow, in combination with mineral oil sulfonates, represent a group of materials excellently suited as additives to the mineral oils in the formulation of rust preventing compounds.

The following formula may be considered as representative of our invention:

Per cent Mineral oil-S. U. viscosity 700" 100 F-.. 90 Nitrated tallow (iodine No. 30) 5 Mineral oil sulfonates 5 slight pre-heating, preferably at 120 to 150 F.

until homogenous.

2 In the evaluations of slushing compounds, it is customary to use the well known Navy salt spray test described in the Proceedings of the A. S. T. M.,

vol. 33, 1933, part I, page 184, and the so-called condensation bath test developed in the industry but not accepted as yet by recognized technical societies. In the Navy salt spray bath, specimens of metal or metal parts are suspended in a corrosion proof non-metallic chamber and subjected to salt water spray. The concentration of salt in the water is 4% NaCl. The spraying is done in -minute periods, twice a day, for five consecutive days. At the end of this period, the specimens must not show any signs of corrosion upon the removal of slushing compounds with solvents.

In the tests given below, our salt spray evalua tions were conducted on an accelerated basis, namely the timeof spraying was increased to 1 A to 2 hours, twice a day. Therefore, the standard requirement for no rusting in five days cannot be applied to the values given below. However, all accelerated tests were made according to the same procedure, so they are strictly comparable.

In the condensation bath test, the specimens are kept in a chamber with rigidly-controlled temperature and humidity. A period of con-, densation of moisture is followed by a drying period, a complete cycle consisting of 24 hours of alternate condensation and drying. The severity of the test can be controlled by the amount of water condensed during the condensation period. In the tests reported below, all specimens were placed in the chamber at the same time and, therefore, underwent the same P 1 cedure.

Product Salt spray bath Condensation bath 700 mineral oil 95%. }O. K. one day Slight corrosion 2nd day. Regular tallow 5%... Rust 2nd day... Considerable corrosion 6th day, p" mineral oil 95%. }O. K. three days Trace of corrosion 4th day. Nitrated tallow 5% Some rust 4th day- Trace of corrosion 6th day.

700" Mineral Oil }O. K. three days Nitrated tallow 10% Trace of corrosion 4th day.

Product Salt spray bath Condensation bath 700 mineral oil 90% Trace of corrosion 3rd 0. K. one day day.

Regular tallow 5% Some rust 2nd day Considerable rust 6th Mineral Oil sulfonates 5% day.

700" mineral oil 90% Nitrated tallow 5% 0. K. five days 0. K. 5 days; trace of Mineral oil sulfonates 5% corrosion 6th day.

Hydro-bromic acid test: This test is specified by certain Government agencies for slushing media for internal combustion engines. For instance, in U. S. Army Ordnance Dept. Specification AXS-G'l, thetest is described as follows: The test consists of dipping the sand blasted steel panels in 0.1% aqueous hydrobromic acid solution and immediately slushing with oil, lubrieating, preservative. medium. After four hours storage in laboratory atmosphere, no more than a trace of corrosion should be apparent.

It will be seen that the test is designed to determine the acid neutralizing ability of the. slushing compound. We give below comparative tests on a slushing compound prepared in accordance with our invention, on one hand, and slushing compounds of conventional type, on the other.

4 to about 20% with good results. Best results are obtainable with concentrations ranging between about 5% and about The mineral oil sulionates are the usual salts of mineral oil sulfonic acids .(usually sodium salt) available in commercial quantities. This ingredient is also effective in amounts from about 1% to about and, here again, the preferred concentrations are between about 5% and about 10%.

The nature of mineral oil employed as a vehicle in the present slushing compounds may vary considerably, depending upon the working conditions and service expected. For instance, for low temperature operations, We may use a mineral oil with a viscosity as low as 70 Saybolt Universal at 100 F., whereas for elevated temperatures, we would prefer to have a more viscous mineral oil,

Condition after exposure to hydro-bromic acid Product 1% hours 4 hours 180 parafiin 0il Very bad Very bad.

rime larg oill. Apprecxable rusting. Appreciable rusting.

time ar 01 20 parafiin on 8 }Apprec1able rustmg. Do. 100 paraflfin oil 97%. Aluminum soap 3% Slight rustmg D0. is t t l i on 53 x I No si ns of rusting irae aow g Mineral 011' sulfona tes 5%..." I 15mg The nitrated tallow of the formula above is a product of reaction between common tallow and concentrated nitric acid. When the two reactants are heated to 220 to 230 F., an exothermic reaction occurs, the temperature rising to 250 to 280 F. without additional heat. The excess mineral acid is washed out with water, upon cooling, and the product is dried. The following table illustrates the properties of the original common The nitrated tallow is representative of a broad group of animal and vegetable fatty oils, such as sperm oil, palm oil, lard oil, and the like, containing unsaturated components and susceptible to nitration. The degree of nitration can be varied and is not limited to the above example. The decrease in iodine number of the fatty oil is a convenient measure of the degree of nitration. While in the above example, the nitrated tallow shows an iodine number 23.8 points lower than the original tallow vs. 53.8), more or fewer nitro groups can be introduced, the upper limiting point being the stability of the solution of the nitrated product in mineral oil; e. g., common tallow can be. nitrated to final iodine numbers ranging from to 5, corresponding to a nitrogen content of 0.75% to 2.75%. For other fatty oils these numerical values are different.

The nitrated tallow or other nitrated fat may be; employed in amounts ranging from about 1% say, about 1200 S. U. V. 100 F. We may also use a petrolatum or blend thereof with mineral oils if a heavier bodied slushing compound is required. In other cases we find it desirable to body up the oil with such thickening agents as aluminum soaps, resins, etc., or, if a thinning effect is desired, we may cut back the oil with solvents. The latter enables us to apply a thin coat product which would leave a viscous film upon the evaporation of the solvent.

We claim:

1. A slushing compound comprising about of mineral oil having'a Saybolt Universal viscosity of about 700 seconds at F., about 5% of nitrated tallow having an iodine number of about 30 and about 5% of mineral oil sulionates.

2. A method for protecting metallic surfaces which comprises applying thereto a slushing compound comprising about 90% of mineral oil having a Saybolt Universal viscosity of about 700 seconds at 100 F., about 5% of nitrated tallow having an iodine number of about 30 and about 5% of mineral oil sulfonates.

3. A slushing compound comprising about 90% of mineral oil havingv a Saybolt Universal viscosity of about 700 seconds at 100 F., from about 5% to about 10% of nitrated tallow having an iodine number of about 30 and from about 5% to about 10% of mineral oil sulfonates.

4. A method for protecting metallic surfaces which comprisesv applying thereto a slushing compound comprising about 90% of mineral oil having a Saybolt Universal viscosity of about 700 seconds at 100 F., from about 5% to about 10% of nitrated tallow having an iodine number of about 30 and from about 5% to about 10% of mineral oil sulfonates.

THEODORE G. ROEHNER.

LOUIS H. SUDl-IOLZ.