Method of evaluating corrosiveness of jet fuel

FIELD: chemistry.

SUBSTANCE: method of evaluating corrosiveness of jet fuel comprises determining the decrease in weight of copper-containing material placed in the fuel before and after testing at high temperature. The copper-containing material used is copper foil which is placed in the fuel and held in hermetically sealed cells in the form of metal vessels at temperature of 150±2°C for 4 hours while holding in two steps of 2 hours each and replacing the fuel after the first step. The greater the decrease in the weight of the copper foil before and after test, the more corrosive the jet fuel.

EFFECT: high reliability and faster evaluation.

1 tbl

 

The invention relates to laboratory methods for the evaluation of corrosivity of jet fuels.

The need to develop a method for evaluation of corrosiveness jet fuels due to the fact that jet fuels allow for a large number of General and mercaptan sulfur (0.25 and 0,003% of the mass, respectively), resulting in their increased corrosiveness to metals at elevated temperatures, and ultimately has a negative impact on the reliability of aircraft.

Contact jet fuel with metals and alloys in the process of operation of aeronautical engineering, chemical corrosion occurs due to the interaction of corrosive sulfur compounds with the metal. Of the metals, copper is the most susceptible to chemical corrosion from corrosive sulfur compounds. Chemical corrosion is estimated at elevated temperatures (100°C and above) of various laboratory methods.

Famous visual method for evaluation of corrosiveness jet fuels according to GOST 6321, involving the assessment of color change of copper after soaking it in fuel for 3 hours at a temperature of 100°C. This qualitative method of evaluation of corrosiveness of fuels included in all domestic standards and international specifications for jet fuel. This method is iswalnum and assess corrosivity of the fuel at a temperature of 100°C.

The closest analogue to the proposed method of evaluation of corrosivity of jet fuels is the method of determining the corrosion activity at elevated temperatures according to GOST 18598. This method provides for testing at 120°C for a duration of 25 hours (5 stages and 5 hours with the change of fuel after each step) and a significant amount of fuel (8 liters) for testing. The disadvantages of this method is not sufficiently high temperature, the duration of the test, a significant amount of fuel testing and a slight decline in the weight of the plate after the test. This method is provided in addition to copper to assess the corrosion activity on the actual alloy bronze WB-NC (containing copper) that is in contact with the fuel. As the experience of the evaluation of corrosivity of aviation fuels according to GOST 18598 using alloy WB-23-NTS, the results are virtually independent of the presence of corrosive sulfur compounds in the fuel and have the same magnitude as for fuels with a high content of mercaptan sulfur (up to 0.005 wt%), and fuels insignificant amount of mercaptan sulfur (less than 0,0003% of the mass).

The task of the invention is to develop a method of evaluation of corrosivity of jet fuels with sufficient sensitivity to corrosionresistant jet fuels, while significantly reducing time and fuel used during the test.

The problem is solved by the method of evaluation of corrosivity of jet fuel, which consists in determining the loss of weight of the copper-containing material is placed in the fuel, before and after the test, at an elevated temperature. The method is characterized by the fact that, as a copper-bearing material using copper foil, which is placed in the fuel and is maintained at a temperature of 150°C for 4 hours (2 stages for 2 hours with a change of fuel after the first stage) in a sealed bombs (metal containers), and the more weight loss of the copper foil before and after the test, the greater the corrosion activity has jet fuel.

Increasing the test temperature to 150°C significantly increases the activity of sulfur compounds in relation to copper. The use of copper foil instead of copper plates allows a noticeable increase its active area, the exposure of the copper foil in the fuel for 4 hours (2 stages for 2 hours with a change of fuel after the 1st stage) allows to obtain a reliable value of corrosivity of jet fuels and significantly reduce the duration of the test (4 hours instead of 25 hours) and the amount of fuel for testing (500 cm3fuel instead of 4000 cm3).

For the evaluation of corrosivity of jet fuels use the apparatus TSRT-2, used nowadays for the evaluation of oxidative stability of jet fuels in static conditions according to GOST 11802. Heating fuel is carried out in a sealed bombs used in GOST 11802.

As the copper-containing material used strips of copper foil having a size of 50×150 mm Before the test strips of copper foil treated with the abrasive cloth (grit abrasive 6-8), grind paste "GOYIM" on felt or felt, washed with petroleum ether (isooctane), rinsed in ethanol and dried between sheets of filter paper. Then strips of copper foil stand for complete drying in a desiccator for 1 hour and weighed with an accuracy of up to is 0.0002, Prepared and weighed strips of copper foil is wound on the coil (made of glass or PTFE) having 4-5 turns (to avoid touching the walls of the glass), and placed in a glass beaker. In a glass pour 125 cm3jet fuel, for a total immersion of a copper foil in the fuel. Then a glass with copper foil, immersed in the fuel, is placed in a bomb and covered with a glass lid. On the bomb run wild with the cover installed on the pressure gauge. The thus prepared samples are placed for 2 hours in the device TSRT-2 having a temperature of 150+/-2°C. the integrity of the bombs controlled by the manometer readings. After 2 hours, the bomb is removed from the device TSRT-2 and cooled in air for about 50-60 mine is. After cooling, the bomb is opened, fuel is drained from the glasses, pour a portion of fresh fuel (125 cm3), close tightly bombs and again placed for 2 hours in the device TSRT-2 having a temperature of 150+/-2°C. After the second stage of the testing of the bomb is removed from the device TSRT-2 and cooled in air for about 50-60 minutes. After cooling, the bomb is opened, the strips of copper foil is removed from the beaker and rinse from the fuel completely immersed in a container with petroleum ether or isooctane. Then the plate is placed on filter paper and using a cotton swab, remove deposits from the surface of the wafer. To remove the remaining deposits and corrosion products plate is placed in a glass pour 30% solution of sulfuric acid so that it completely covered the surface of the plate. Plate several times using tweezers to move in solution. After 5 minutes, the plates are removed and cleaned from sediments and corrosion with a brush or cotton swab, washed three times with distilled water, get wet filter paper and placed in a desiccator for complete drying for 1 hour. Then the plates are weighed with accuracy is 0.0002,

Corrosivity jet fuels appreciate the reduced mass of the plate before and after the test.

The invention is confirmed by the use of the AMI, presented in the table.

As can be seen from the table, the proposed method has sufficient sensitivity to corrosive jet fuels containing no more than 0,003% of the mass, mercaptan sulfur, in contrast to the method according to the prototype, for which the weight loss of the plate in the evaluation of corrosivity of jet fuels with the content of mercaptan sulfur not more than 0,003% of the mass is close to the accuracy weighting (0.0002 g). This is especially important with the introduction of the Technical Regulations on 27.02.2008 No. 118 (2013 Technical regulations of the Customs Union 013/2011), according to which in jet fuels is limited to the content of mercaptan sulfur not more than 0,003% of the mass.

Thus, the use of copper foil instead of copper plates in the proposed method allows to significantly increase its active area, the exposure of the copper foil in the fuel for 4 hours (2 stages for 2 hours with a change of fuel after the 1st stage) allows to obtain a reliable value of corrosivity of jet fuels and significantly reduce the duration of the test (4 hours instead of 25 hours) and the amount of fuel for testing (500 cm3fuel instead of 4000 cm3).

Table
The definition of corrosivity of jet fuels
№ p/pMark of jet fuelThe content of mercaptan sulfurWeight loss of the copper plate, g
GOST 18598(prototype)The proposed method
1TS-10,00040,00050,0029
20,002is 0.00020,0040
30,0030,00750,0090
40,00390,00850,0100
50,0040,00420,0110
60,00420,00830,0090
70,00450,00670,0098
80,00500,01220,0133
9RTOTC0,00040,0018
10OTC0,00050,0015
11OTC0,00070,0030
12OTC0,00080,0030
13OTC0,00140,0043
14OTC0,00000,0015
15T-6OTC0,0004,0028
16OTC0,00050,0030
17OTC0,00060,0038

The way to assess the corrosion activity of jet fuel, which consists in determining weight loss of copper-bearing material in the fuel, before and after the test, at elevated temperature, characterized in that as the copper-bearing material using copper foil, which is placed in the fuel and incubated in a sealed, bombs, made in the form of a metallic vessel, at a temperature of 150±2°C for 4 hours when carrying out exposure in phase 2 for 2 hours with a change of fuel, and the more weight loss of the copper foil before and after the test, the higher corrosion activity has jet fuel.



 

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