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THE INVESTIGATION
The oils used tor this investigation were received direct trom the manufacturer in cases of quarts and gallons which had not been opened prior to being received at the Lubrication Laboratory at Virginia Poly-technic Institute Quaker State, s.A.E. 30, is a non-solvent refined oil of Pennsylvania Crude.
Esso Motor Oil. No. 31 is a solvent refined oil of mixed base crude with « Paraflow » and « Paratone » added.
The new oils contormed to the following specifications:
Federal-1’~ogul Corporation, Detroit, Michigan, in the form ot bars one and one-eighth inches in diameter by seven and one-halt inches long. ‘I.he bars were cut on a milling machine in the shops at Virginia Polytechnic Institute to samples one-tenth inch thick and machined to one and one-sixteenth inches in diameter.
EQUIPMENT
Several types of testing apparatus were used during the investigation; these will be described below and designated by name which will serve to identity them in later discussion.
li>jET-TYJ?E OIL BA’IH. The « Jet-type oil bath » consisted ot a rectangular box constructed of unfinished, welded, sheet steel ten inches long, four inches wide, and tour inches deep. A one-eighth inch pipe (nominal) extended the length ot the box equidistant from the sides, one and one-halt inches below the top edge. This pipe served as a manifold and was connected by means ot a tee at the center to the pump. Five one-sixteenth inch holes were drilled one inch apart in the bottom side ot the manifold on each branch ot the tee. Steel wire hangers were placed on this manifold, between each pair ot holes, to hold the sample discs.
Figure l, page 16, shows the general layout of the oil bath together with the manner in which the bearing specimens were held by the « U » type hangers.
Two lengths of one-eighth inch pipe were run through one side ot the box, the top being connected to the tee in the manifold, and the bottom one being welded in place to act as a drain.
The top of the spray box was made trom a thin piece of sheet steel bent to the shape ot a very shallow V to allow condensed oil vapors to drip back into the bath. A hole was drilled in the center ot this cover to receive a thermometer.
The circulating system consisted of a Chevrolet oil pump (vane type) fitted with a packing gland. This pump was mounted on wooden supports at approximately the same ~ight as the spray box; and was driven by a one-quarter horsepower eleotrio motor through a flexible coupling at approx-imately 1725 r.p.m.
The spray box was placed on top of a Hoskins hot plate of twelve hundred watts capacity connected in series with a variable resistance to facil.:itate temperature adjustment and control. No insulation was placed on the bath.
This is the same apparatus as was used by ~ydnor (16) for corrosion determinations at the Virginia Polytechnic Institute, Lubrication Lab-oratory, during the year 1935-1936.
MODIFIED .TEr-TYPE OIL BATH. The essential features of the original bath explained above were maintained in the modified apparatus. Certain refinements and enlargements to enable two tests to be run at the same time were added.
A rectangular box of the same material as before, sheet steel, was constructed to the following dimensions; ten inches long, eight inches wide, and four inches deep. A dividing wall ran the length of the box separating it into two equal compartments, ten inches by four inches by four inches. The piping to and from the bath was the same as described above, one side being the mirror image of the other. Figure 2, page 18, illustrates diagram-matically the design of this apparatus. However, in addition to the one one-eighth inch drain pipe {which had previously been connected directly to the suction of the pump), a one inch pipe was welded two inches from the top edge of the long aide, providing a gravity overflow to maintain theproper level in the oil bath. The one-eighth inch pipe drained from the bottom of the bath to prevent stratification of the oil.
Both drain pipes emptied into a three inch pipe sixteen inches in length, set at an angle of thirty-six degrees which was used as an oil sump containing the intermittent electrical heaters. These heaters were three hundred watt capacity copper tube type, and were in series with a power relay which was in turn actuated by a three volt d.c. relay controlled by a De .Khotinsky type thermo-regulator according to the circuit given below.
The oil sump was connected at the bottom through a one-eighth inch pipe to the oil pumping mechanism which was described under I. JET-TYPE OIL BATH, page 15.
The type of hanger used with this equipment was modified :from the · « U » type to what will be designated as the »sn type. This consisted of a piece of three sixty-fourths inch piano wire wound around the manifold and extending below the pipe between the or.. »‘(‘icea in the form of a hook. The samples were drilled one-eighth inch from the outer edge by a one-sixteenth inch bit to be hung in this manner.
With this set-up the tube heaters operate intermittently in conjunc-tion with the constant heat supplied by the hot plate to give reasonably accurate temperature control (range± 2 or 30 F).
GLASS APPARATUS.
A one liter beaker was wound externally with 450 watt chromel heating element and placed in a three liter beaker. The annular space between the beakers was filled with flaked asbestos. The three liter beaker was in turn covered by a one inch layer of 8&l magnesia pipe covering. The heating unit was connected in series with the relays and thermo-regulator as was outlined under II. MODIFIED JET-TYPE OIL BATH, page 19. The cadmium plated thermo-regulator was protected from the oil by surrounding it with a glass test tube filled with light mineral oil. Agitation of the oil was accomplished by rotating the specimen discs on a glass rod of three-sixteenths inches diameter. A hole seven thirty-seconds or an inch in diameter was drilled through the center of each specimen to receive the glass rod. The stirring device was clamped in a pulley block driven by an electrical stirring motor. Spacers of nine thirty-aeconds of an inch outside diameter held the samples one inch from the bottom of the beaker and seven-sixteenths inches apart. Figure 3, page 21, shows diagranmatically the assembly of the glass apparatus.
In all teats but one air was injected into the oil bath through a glass tube drawn to approximately one-half millimeter internal diameter. Air was obtained and controlled by allowing water to fill a sealed five gallon carboy which in turn caused the trapped saturated air to be forced through the glass tube into the oil bath.
PROCEDURE
The following test procedure was observed in all runs regardless of the equipment. After the initial treatment, which was varied considerably from run to run, the specimens were washed in gasoline, alcohol, and dried in an electric oven at 220° F to constant weight. The test bath was first thoroughly washed with gasoline, scrubbed with a brush, and finally rinsed in gasoline prior to each test. In the cases where piping was used, gasoline was circulated to clean out aIJY oil deposits. At the termination of a run, specimens were washed in gasoline, wiped with a soft cloth to remove aIJY material adhering to the surface, rinsed in alcohol and dried at 220° F to constant weight.
The method of PROCEDURE is given below on the basis of the type of equip-ment which was used. Tb.is was to f’acil. .i tate ease of reading due to the fact that a different method of procedure was used in each specific type of equipment.
Equipment I
Bearing specimens were worked on a flat surface to a finish obtain-able with 0000 emery paper. D.ie to the curvature, the edges of the discs were never as highly polished as the faces.
During the test period the o~ice holes were cleaned every twelve hours by forcing a wire through them.
Equipment II
Run Nos. 5 and 6 did not have oil sump, thermo-regulators, and « S~ type haDgers attached.
The samples were :finished with emery paper as described under A above, for Run Nos. 5 through 12.
In an attempt to control the flow of oil in each bath to more nearly the same rate, Run Nos. g through 16 were made with the oil t’low controlled by an oritice placed in the suction line of each pump. The adjustment was made using water as the fluid in place of the oil. All rates of flow are expressed in terms of water iDBtead of oil due to the di:t’f’ioulty of measuring oil flow at the temperatures encountered. The velocity of flow observed was approximately 0.67 feet per second through each jet.
In place ot’ the polishing process for finishing, the specilnens for Run Nos. 13 through 16 were treated with a 30~ solution of nitric acid (sp. gr. 1.190). The samples were placed in the acid until the action became vigorous at which time the surface was assumed to be free from dirt and were then washed in running water for a period of twohours before rinsing in alcohol and drying to constant weight.
Equipment III a
It was believed that the nitric acid action iLduced passivity thereby preventing corrosion. To prevent this specimens for Run No. 17 were treated with a solution of aqua regia made up as toliows:
25 parts nitric acid (cone.)
75 parts hydrochloric acid (cone.)
300 parts water
The samples were etched in this solution, cleaned, and dried as usual. The same specimens were used in Run Noa. 18 through 20 as were used in Run No. 17. Microscopic examination previous to each test showed the surface characteristics unaltered.
Equipment III b
The same samples were used in Run Nos. 21 and 22 as were used in Run Nos. 17 through 20.
The copper plate was removed from the bath during Run No. 23. one sample of Cadmium-Silver-Copper (bearing VIII) was placed in electrical contact with a copper-lead bearing (V) through the medium or the iron stirring rod. Both samples were treated with aqua regia etch prior to cleaning and drying by the usual method.
Equipment II
Equipment II was altered as follows for these runs: ‘!’WO five sixty-fourths inch holes were drilled one inch apart on each side of the tee in the manifold so as to accomodate two specimens in each bath. Thespeci1nens were insulated from each other by glass « S » type hangers. The orifices were kept in the suction line, maintaining the total flow, but increasing the flow from each ot the four jets.The velocity of flow from each jet was equal to 1.51 feet per second.
New samples were used in each case, and were treated with the aqua regia etch prior to drying in the usual manner.
Introduction
II. Historical
Need For Wew Bearing Ketals
Presence Of Oxygen
Hetarding Effects Of The Products Of Corrosion
Effects Of Temperature
Break-In-Oils, Fatty Acids, and Oiliness Compounds
Electrolytic Theory Of Corrosion
Corrosion By Direct Chemical Attack
Factors Influencing Both Electrolytic Corrosion And
Corrosion By Direct Chemical Attack
III. The Investigation
Materials
The Bearing Metal 3air~les
3tructure Of The Bearing Ivietals
Specific Gravity Of The Bearing Metals
Equipment
Jet-Type Oil Bath
Modified Jet-Type Oil Bath
Glass Apparatus
Modified Glass Apparatus
Procedure
IV. Data And Results
Discussion Ot The Test Data
Length Of Time For Corrosion To Start
The Effect Of Oil Stability On The Rate Ot Corrosion
Length Of Time Required For Test
Effect Of Alox AA Compound
Effect Of A Different Oil
Etfect Of Air At The Interface And scrubbing Action
Of The Oil .:ltream
Effect Of Electrolytic Action And Jcrubbing Action
Summary Of Discussion Relative To Conditions For
V. Conclusions
VI. Summary
VII. Bibliography
GET THE COMPLETE PROJECT
THE MECHANISM OF COlBOSION OF CADMIUM-SILVER-COPPER BEARING ALLOYS
