What rust inhibitors are there in the coolant (lathe processing)?

1. What kinds of coolant are there? What are the characteristics?

Coolant is composed of water, antifreeze and additives, which can be divided into alcohols, glycerol and ethylene glycol according to the composition of antifreeze. Its characteristics are as follows:

① Alcohol cooling liquid uses ethanol (commonly known as alcohol) as antifreeze, which has low price, good fluidity and simple preparation process, but it has been gradually eliminated because of its low boiling point, easy evaporation loss, easy rise of freezing point and flammability.

② Glycerol-type coolant has high boiling point, low volatility, incombustibility, non-toxicity and low corrosiveness, but its freezing point lowering effect is not good, its cost is high and its price is expensive, which is unacceptable to users, and only a few Nordic countries still use it.

(3) The ethylene glycol type cooling liquid is prepared by using ethylene glycol as antifreeze and adding a small amount of defoamer, preservative and other comprehensive additives. Because ethylene glycol is easily soluble in water, it can be made into various freezing points, and its lowest freezing point can reach -68℃. This kind of cooling liquid has the characteristics of high boiling point, low foam tendency, good viscosity-temperature performance, anti-corrosion and anti-scaling, and is an ideal cooling liquid.

At present, almost all the coolants used by engines at home and abroad and sold in the market are this kind of ethylene glycol coolant.

2. How many specifications are there in China's current antifreeze standards?

China's current standard SH 052 1-92 ethylene glycol cooling liquid and its concentrated solution system are based on ethylene glycol, with 3% ~ 10% antirust agent and appropriate amount of water. There are seven specifications, and their freezing points are shown in Table 2. 1. When in use, the appropriate specifications can be selected according to the lowest temperature in local or local areas.

Table 2. 1 antifreeze specifications

standard

concentrated solution

-25th.

-No.30

-No.35

-No.40

-No.45

-No.50

Freezing point/degree Celsius

Not higher than ≤

-37

-25

-30

-35

-40

-45

-50

3. What are the main properties of automobile antifreeze? How to measure?

The main physical and chemical properties of automobile antifreeze reflect the performance of antifreeze to a certain extent, which can help users choose antifreeze by measurement.

(1) relative density (ASTM D 1 122, SH/T 0068)

It is mainly used to estimate the contents of ethylene glycol and various salts in antifreeze. Relative density is also related to heat transfer. In addition, the anti-freezing ability of antifreeze can be measured by the combination of relative density and refractive index.

(2) Freezing point (ASTM D 1 177, Shanghai /T 0090)

It can be used to estimate the minimum service temperature of antifreeze and the ethylene glycol content in it. Put 75 ~ 100 ml sample in a test tube, cool it at a certain speed, measure the temperature of antifreeze, and draw a time-temperature curve. The inflection point when the curve reaches the level is the freezing point.

(3) boiling point (ASTM D 1 120, SH/T 0089)

Used to evaluate the high temperature service limit of antifreeze. Put 60mL sample into a 100mL short-necked bottle with reflux condenser, heat it to reflux, and measure the temperature of liquid phase after 2min to get the boiling point.

(4)pH value (ASTM D 1287, SH/T0069).

At present, only the pH value of diluent is determined. The pH meter was connected to the glass calomel electrode for determination.

(5) reserve alkalinity (ASTM D 12 1 1, SH/T009 1)

Used to determine the change process of pH value of antifreeze in use, or to determine the buffering capacity of antifreeze. Take 100mL sample and dilute it with distilled water to 100mL. When the pH is 5.5, titrate it with 0. 1mol/L hydrochloric acid potential to the required ml number.

(6) Foam tendency (ASTM D 188 1, SH/T 0066)

Foam will affect heat transfer, so a good antifreeze should not produce a lot of foam. Introduce a certain rate of air into the antifreeze, and record the foam volume and defoaming time after stopping blowing. Japan's JIS standard is to measure the foam volume after 100 strong vibration. This method is crude, but simple. The ASTM standard adopts the method of diffusion head dispersion, which is not only difficult to find materials, but also difficult to repeat.

(7) Corrosion test (ASTM D 1384, Shanghai /T 0085)

This is the most important engine coolant corrosion test method. The metal parts (25cmV╳5cm), cast iron, cast aluminum, copper, solder and steel commonly used in six cooling systems were soaked in antifreeze, and air was continuously introduced at 88 oC for 336h h. After the test, the weight changes of the specimens were measured, and the appearance changes of the specimens and antifreeze were observed. The Japanese JIS standard increases the properties of the solution after the test and the state of each component, and the index is stricter than ASTM.

4. What is the function of coolant with antifreeze?

The most widely used antifreeze coolant is ethylene glycol coolant. In addition to antifreeze, this kind of cooling liquid also contains many additives such as scale inhibitor, corrosion inhibitor and defoamer, so it has many functions. Therefore, we should strongly advocate the use of coolant containing antifreeze in automobile engines.

(1) antifreeze

The main function of coolant is to prevent the coolant from freezing and cracking when parking in cold winter.

Radiator and frozen engine block or cover. The main index is the freezing point of coolant. When selecting or preparing coolant, its freezing point should be about 10 oC lower than the lowest temperature in this area, so as to ensure that antifreeze will not freeze under special circumstances.

(2) Anti-boiling

The boiling point of coolant can reach 107 ~ 1 10 oc, which effectively prevents the engine from boiling in summer and keeps the engine working at normal temperature. Its main index is boiling point.

(3) Corrosion protection

The cooling system of modern automobile engines mostly adopts cast aluminum and aluminum alloy parts, and the coolant has protective effect on cast iron, copper and cast aluminum.

(4) waterproof scales

Scale is caused by insoluble salt or oxide crystals attached to the surface of radiator. The generation of scale not only affects the normal heat dissipation of the radiator, but also easily causes the blockage of the circulating pipeline of the cooling system, which leads to the high water temperature and seriously affects the normal work of the engine. Coolant has descaling function, and the descaling rate reaches 98 oC.

5. What principles should be followed when choosing antifreeze?

① Select the freezing point of antifreeze according to the ambient temperature conditions. The freezing point of antifreeze is one of the most important indexes of antifreeze, and it is also an important condition for antifreeze to prevent freezing. In general, the freezing point of antifreeze should be about 10 ~ 15 oc lower than the local lowest temperature in winter. If the local minimum temperature is -30℃, the freezing point of antifreeze should be lower than -45℃.

② Choose antifreeze according to different requirements of vehicles. Under normal circumstances, imported cars, domestic cars and high-end cars should use permanent antifreeze (service life is 2 ~ 3 years), and ordinary cars can use direct antifreeze.

③ Choose antifreeze according to the number and concentration of vehicles. Units and departments with a large number of vehicles and relatively concentrated vehicles can choose small packaging antifreeze mother liquor with stable performance. Because the package is compact, it is convenient for transportation and storage, and it can be flexibly modulated according to different environments, use conditions and different work requirements, thus achieving the purpose of saving and practicality. In the case of few or scattered vehicles, you can choose to use antifreeze directly.

(4) Generally, antifreeze with rust-proof, corrosion-proof and descaling ability should be selected. The most important thing about antifreeze is rust prevention. So choose brand-name products. Preservatives, corrosion inhibitors, scale inhibitors and cleaning agents are added to these products, and the quality of the products is guaranteed.

⑤ Select antifreeze matching with rubber sealing conduit. The antifreeze should have no side effects, such as swelling and corrosion of rubber sealing ducts.

6. When using concentrated solution, what is the effect of adding different amounts of water on freezing point?

There is also an antifreeze mother liquid in the antifreeze products supplied by the market, which is concentrated antifreeze. This kind of antifreeze is generally produced by imported products or joint ventures, and is usually packed in small iron drums, such as Lipton and Shell.

Concentrated antifreeze, that is, antifreeze mother liquor, cannot be used directly. It should be prepared into a certain concentration with softened water according to the requirements of using temperature. See Table 6. 1 for the corresponding relationship between the concentration of ethylene glycol antifreeze mother liquor and freezing point. Soft water for blending refers to deionized water or distilled water (well water or tap water cannot be used).

Table 6. 1 Preparation concentration and freezing point of antifreeze mother liquor

Freezing point/degree Celsius

glycol

Concentration/%

Density (20 degrees Celsius)

/(mg/cm3)

freezing point

glycol

Concentration/%

Density (20 degrees Celsius)

/(mg/cm3)

- 10

28.4

1.0340

-40

54

1.07 13

- 15

32.8

1.0426

-45

57

1.0746

-20

38.5

1.0506

-50

59

1.0786

-25

45.3

1.0586

-45

80

1.0958

-30

47.8

1.0627

-30

Eighty-five

1. 100 1

-35

50

1.067 1

- 13

100

1. 1 130

7. Why can't I add antifreeze mother liquor directly?

Some drivers and maintenance workers think that the purer antifreeze is, the better, and the higher the concentration of ethylene glycol is, the better. Adding antifreeze mother liquor directly will not only cause waste economically, but also make antifreeze fail to meet the freezing point requirements.

It can be seen from Table 6. 1 that the freezing point of ethylene glycol antifreeze changes with the concentration of ethylene glycol in aqueous solution. When the concentration is lower than 59%, the freezing point of ethylene glycol in aqueous solution rises and falls. But when the concentration exceeds 59%, the freezing point rises with the increase of ethylene glycol concentration, and when the concentration reaches 100%, the freezing point rises to -65438.

In addition, there will be other unexpected phenomena when adding antifreeze mother liquor directly, such as deterioration of antifreeze, high concentration, high density, high viscosity at low temperature, high engine temperature and so on. Therefore, when using antifreeze mother liquor, it must be prepared as required, and direct use is prohibited.

8. What should I pay attention to when using coolant?

Proper use of coolant can play the role of corrosion prevention, radiator boiling, scale prevention and antifreeze, so that the cooling system is always in the best working state and the normal working temperature of the engine is maintained. If you don't pay attention in use, it will damage the cooling system and seriously affect the performance and service life of the engine, so you should pay special attention in use.

(1) Choose antifreeze according to the temperature.

According to the local lowest temperature in winter, choose the antifreeze with appropriate freezing point brand, and the freezing point should be at least lower than the lowest temperature 10oC. If it is a concentrated solution, it should be diluted with soft water according to the proportion specified in the product manual.

(2) Use after verification.

When the antifreeze is stored for a long time, or products with abnormalities (rust residue and other deposits) are found, it should be tested after quality inspection (put in the refrigerator for testing) to determine whether it can be used.

(3) Rational use of antifreeze

The service life of antifreeze coolant is long, generally 1 ~ 2 years (long-term antifreeze can reach 2 ~ 3 years), it is alkaline, and its pH value is generally between 7.5 ~ 1 1.0. If the pH value is lower than 7.0 or higher than 1 1.0, it shall be scrapped and replaced in time.

In use, if the liquid level of the radiator drops due to the leakage of the cooling system, the coolant of the same brand should be replenished in time. If the liquid level drops due to the evaporation of water, distilled water or deionized water should be added to the cooling system, and hard water such as well water and tap water should not be added. When there is suspended matter, sediment or peculiar smell in the cooling liquid, it proves that the cooling liquid has undergone chemical reaction, deterioration and failure. The cooling system should be cleaned in time, and all coolant should be replaced.

Before adding new antifreeze, completely drain the cooling water, and then clean the cooling system with clean water; If the scale and corrosion are serious, wash the radiator carefully and thoroughly check the cooling system. If there is water leakage, it should be repaired thoroughly.

Due to the high price of antifreeze, don't overdo it when filling it. Generally, it can only be added to 95% of the total capacity of the cooling system to avoid overflowing after heating and expansion. Don't open the water tank cover immediately after parking.

(4) prevent pollution

The ineffective antifreeze can be recycled and not spilled at will to prevent water pollution and waste.

(5) prevent mixing.

Different brands of coolants should not be mixed, so as to avoid chemical reaction and damage their comprehensive anti-corrosion ability.

(6) Human body protection

Antifreeze (ethylene glycol) is toxic and irritating to human skin and internal organs. Do not inhale with your mouth during use. Wash your hands in time after contact, and rinse with clear water in time if it spills into your eyes.

9. Why should the coolant containing antifreeze be used all the year round?

Many drivers use engine antifreeze in winter and tap water in summer. This method was thought to be economical, but it left a serious problem for the engine. Water can be used to cool the engine in summer, but using water as engine coolant has many disadvantages. For example, minerals in tap water are easy to produce well-insulated scale at high temperature, which covers the water jacket, radiator, temperature sensor and temperature control switch, causing the temperature to get out of control and the cooling fan to start too late, forming a "vicious cycle of overheating", which is the main reason for such failures of automobile engines in summer. The boiling point of water is 100oC, which cannot meet the requirement of high normal water temperature (95 ~ 105 oc) of modern automobile engines. In summer, the engine often boils, and a large amount of steam rushes out of the radiator cover and enters the expansion box. Due to the limited volume of the expansion tank, it can't contain a large amount of water vapor, which further leads to the occurrence of malignant faults such as washing the cylinder gasket, warping and deformation of the cylinder head, and burning the tile during cylinder pulling. Water also has a certain corrosive effect on the cylinder block.

In addition to antifreeze, various additives such as scale inhibitor, corrosion inhibitor and defoamer are added to the coolant with antifreeze, so it has many functions such as anti-boiling, and its boiling point can reach 107 ~ 1 10oC, which can effectively prevent the engine from "boiling" in summer. Scale removal function, the scale removal rate reaches 98%; Anti-corrosion function, protecting cast iron, copper and cast aluminum; Anti-freezing function, its freezing point can reach-15 ~ 60oC, which can effectively prevent the cylinder block and radiator from freezing and cracking in winter. Therefore, coolant containing antifreeze should be used all year round.

10. How to check the coolant?

It is easy to check the amount of coolant, but wait until the engine stops running and completely cools down. It is not easy to see accurately because the level of coolant will change when the engine is running. Under normal circumstances, the height of the coolant should be between the highest and lowest points of the scale. If the coolant increases abnormally, there is a potential problem with the engine. You can drain the excess coolant first, let it fall between the highest point and the lowest point, and then check it constantly. If the coolant continues to rise, it should be repaired immediately; If the coolant level drops below the lowest point, it means that the engine is short of water and will heat up, which will cause the cylinder to deform or burn out the cylinder gasket in severe cases. If the coolant is supplemented, it is best to use the same brand products specified by the manufacturer. Of course, in an emergency, water can also be added. If the color of the coolant becomes dark and turbid, it means that the quality is degraded and needs to be replaced.

1 1. How to change the coolant (antifreeze) correctly?

① First, turn off the engine and let it cool, so as not to cause harm to the human body because the water temperature is too high when replacing the coolant.

(2) After parking, check whether there is a lot of water under the car and whether there is water in the engine room. If the coolant leaks, find out the cause and repair it to ensure that similar faults will not occur after replacing it with new coolant.

③ After the engine cools down, turn the heater switch on the instrument panel to one end before discharging the coolant, so as to completely open the heater control valve.

④ Unscrew the cover of the coolant expansion tank (balance storage tank or water tank), and pay attention to wait until a part of it is loose to weaken the high-pressure air flow inside before completely unscrewing the cover.

⑤ Loosen the hose clamp at the water pump port, pull out the coolant hose and release the coolant.

⑥ Check the state of coolant. If the cooling system needs to be cleaned, add enough clean water and cleaning solution, and clean it at idle speed 10 ~ 30 min (the time depends), then release the cleaning solution, and rinse it with clean water 1 ~ 2 times until the released clean water is clean, and then clamp the drainage hose.

⑦ Select the appropriate coolant according to the climate and vehicle conditions. Be careful not to use tap water, streams or even roadside water as coolant. Slowly add coolant to the expansion tank until the liquid level is flush with the highest mark.

⑧ Tighten the expansion box cover and start the engine until the fan runs for 2 ~ 3 minutes.

Pet-name ruby engine flameout, check the coolant level, add enough when necessary.

Attending always check the coolant level during driving, replenish it when it is insufficient, and keep the remaining coolant sealed.

12. Is the color of antifreeze related to its performance?

There are many colors of antifreeze on the market now, such as: Great Wall multi-effect antifreeze is fluorescent green, Caltex super antifreeze is orange, Bluestar antifreeze is blue, and Tongli antifreeze is red. Antifreeze itself is a colorless and transparent liquid. The reason why these antifreeze solutions are made into bright colors is mainly because some dyes are added, which is easy to distinguish and distinguish, and another function is to prevent eating by mistake. Therefore, the color of antifreeze is only a sign, which is determined by the dye used, and is not necessarily related to performance and quality.

13. Can I choose antifreeze by "tasting"?

Some users use the method of "tasting" when choosing antifreeze, saying that sweet is "good antifreeze" and bitter is "bad antifreeze". Is this method scientific?

The main reason why users adopt this method is that the main component of antifreeze is aqueous solution of ethylene glycol or propylene glycol, both of which are sweet. In order to reduce the cost, some famous brand products use cheap and bitter methanol or fusel, the leftover from wineries, instead of ethylene glycol or propylene glycol. Although the required freezing point can be obtained, these two substances are easy to "boil" because of their low boiling points, so the antifreeze can be identified by "tasting" to some extent. However, this method is unscientific, because the leftover methanol or fusel from wineries is very toxic, which may lead to blindness or even death after taking it. In addition, it is difficult to determine the anticorrosion performance of antifreeze by this method. Some products that fail to pass the formal inspection are often highly corrosive and will cause damage to the cooling system of automobiles. Some antifreeze will also corrode the water tank and pump it into the engine, causing serious accidents. Therefore, users are advised to choose regular brand antifreeze when choosing antifreeze.

14. How to identify fake antifreeze in a simple way?

Inferior antifreeze can be identified by the following simple methods.

(1) Measure the freezing point

You can put antifreeze in a transparent bottle and then put it in the refrigerator 1 ~ 2 days, and adjust the temperature of the refrigerator to the freezing point of antifreeze. After taking it out, observe the transparency and flowing state of antifreeze in the bottle. If there is ice slag, the freezing point is unqualified.

(2) measuring pH value

Drop one or two drops of antifreeze on the pH test paper and observe the color change of the test paper. Qualified antifreeze is alkaline (pH > 7). If it is acidic, it is unqualified and cannot be used.

(3) Measuring corrosivity

Put antifreeze in glass or glass bottle, and put iron wire, copper wire and aluminum wire. If possible, it is best to put the glass in a constant temperature water bath of 80 ~ 90 oc. If there is no constant temperature water bath, you can directly heat it to this temperature range, heating it 3 ~ 4 times a day and soaking it for 3 ~ 5 days. Take out the wires above and observe them. If it rusts, it is an unqualified product and cannot be used.

15 why can't different brands of antifreeze be mixed?

In addition to preventing the coolant from freezing the radiator and freezing the engine cylinder block or cover when parking in cold winter, antifreeze has another important anti-corrosion function, so preservatives need to be added to antifreeze, but different brands of antifreeze use different preservatives, and some of them are very different. For example, preservatives that are effective for ferrous metals often have corrosive effects on aluminum products, while aluminum products preservatives have corrosive effects on iron. When different brands of antifreeze are mixed, the preservatives in them will react chemically, which will affect the anti-corrosion effect and even produce corrosive substances after the reaction, so different brands of antifreeze cannot be mixed.

16. What is the cause of boiling or foaming of coolant?

(1) Boiling water is overheated

Overheated boiling water is a common phenomenon. If the engine temperature is too high, the water in the radiator will boil and a lot of water will be turned out. If you don't pay attention to spraying water, you will burn yourself. The causes of overheating are: the radiator is short of water, the heat dissipation is not good, the shutter fails, the water pump is damaged, the fan belt is too loose and the thermostat fails.

(2) Water retaining and water turning

Blockage of cooling system is one of the common faults of engine. Because of the blockage, the cooling water circulation is not good, which leads to the radiator turning over. The reason for this failure is that the radiator is blocked or the outlet pipe is deflated, which has nothing to do with temperature. Because the antifreeze is not changed for a long time, the dirt in the antifreeze is easy to block the radiator core tube. After blocking, the cross-sectional area of antifreeze is greatly reduced, and more antifreeze flows into the radiator than out, and antifreeze accumulates in the water supply room. Because the pump pressure is high when filling the valve, water can only pass through the radiator core pipe that is not completely blocked, and the antifreeze accumulated in the water supply room is transferred out from the water supply port when the throttle is released. Therefore, when the congestion is not too serious, the performance is that the throttle is full of water and does not turn, and the throttle is released. It is easy to find when the radiator is completely blocked, but it is not easy to find when it is slightly blocked.

(3) gas and water flow through and turn over the water

This phenomenon mostly occurs in cars that have passed the overhaul period, and this kind of fault is difficult to judge and eliminate. Gas-water channeling refers to the high-pressure gas in the engine cylinder rushing into the waterway. Under the action of extra high-pressure gas, the antifreeze in the engine water channel makes the water flowing into the radiator water chamber through the water inlet pipe increase sharply, causing the radiator to fall over.

(4) Used products are mixed with antifreeze, causing water to boil.

When adding antifreeze, the container should be clean and the water tank should be clean. If petroleum products are mixed into antifreeze by mistake, the additives in antifreeze will be ineffective, resulting in a large number of bubbles, which will affect the heat dissipation efficiency and even overflow from the water tank cover.

(5) Excessive addition of antifreeze causes swelling and water boiling.

Due to the large thermal expansion of antifreeze, only 90% of the volume of the water tank can be filled when filling, and the expansion space will flow out on the radiator, otherwise it will be added.