Antifreeze in the automotive industry and rapid detection

February 24, 2023

First, the application of antifreeze in the automotive industry

In winter, the temperature is low. In order to keep the car in use at low temperatures in winter, the engine coolant has added some substances that can reduce the water freezing point as an antifreeze, keeping the cooling system from freezing during cold weather. Therefore, people sometimes refer to coolant as "antifreeze" or "antifreeze." The full name of antifreeze should be called antifreeze coolant, which means coolant with antifreeze function.

1. Definition

Antifreeze, also known as coolant, is a liquid composed of antifreeze additives and additives that prevent metal from rusting and water. It needs to have freeze resistance, corrosion resistance, thermal conductivity and non-deteriorating properties. Ethylene glycol is now often used as the main ingredient, adding anti-corrosion additives and water antifreeze.

The engine cooling system of an internal combustion vehicle is a liquid-cooled closed loop system consisting of a cylinder, a jacket and a water tank. The working status of the cooling system directly affects the normal operation of the vehicle and the service life of the vehicle. Antifreeze is the cooling medium of the circulating cooling system of an internal combustion engine. It is mainly composed of antifreeze, corrosion inhibitor, defoamer, colorant, mildewproofing agent and buffer. With the development of the automobile industry, the performance requirements of the engine are getting higher and higher. Not only does the antifreeze require a lower freezing point and a higher boiling point , but it also has good metal corrosion resistance, cavitation resistance, and anti-knot. Scale performance, as well as comprehensive performance in terms of environmental pollution or environmental pollution, long service life, etc.

2. Kind

(1) Ethylene glycol antifreeze

Ethylene glycol is a colorless, slightly viscous liquid with a boiling point of 197.4°C and an ice-point of -11.5°C that mixes with water in any ratio. After mixing, the freezing point decreased significantly due to the change in the vapor pressure of the cooling water. Ethylene glycol antifreeze is easy to produce acidic substances in use, and has a corrosive effect on metals. Therefore, an appropriate amount of disodium hydrogen phosphate or the like should be added to prevent corrosion. Ethylene glycol is toxic, but because of its high boiling point, it does not produce vapor that is inhaled into the body and causes poisoning. Ethylene glycol is highly water-absorbent and storage containers should be sealed to prevent overflow after water absorption. Since the boiling point of water is lower than that of ethylene glycol, water is used to evaporate during use. When there is a lack of coolant, only water is added. This antifreeze can be recovered after use (to prevent the incorporation of petroleum products ), after precipitation, filtration, add water to adjust the concentration, add preservatives, and can continue to use, generally available for 3-5 years. However, it must be filtered many times to prevent damage to the car. Many people think that the freezing point of ethylene glycol is very low, and the freezing point of antifreeze is a neutralization freezing point after glycol and water are mixed in different proportions. It is not true. After mixing , the freezing point will only change the vapor pressure of cooling water . Significantly lower. The degree of reduction decreases with increasing ethylene glycol content within a certain range, but once it exceeds a certain percentage, the freezing point will rise instead . When the content of ethylene glycol is 68%, the freezing point can be reduced to -68°C. When this limit is exceeded, the freezing point should rise instead. The antifreeze mixed with 40% ethylene glycol and 60% soft water has an anti-freezing temperature of -25°C. When the antifreeze contains 50% of ethylene glycol and water, the freezing temperature is -35°C.

(2) Diethylene glycol antifreeze

Diethylene glycol - water antifreeze, not volatile and fire, but also less corrosive to metals, but the effect of lowering the freezing point of diethylene glycol is lower than that of ethylene glycol. When preparing antifreeze at the same freezing point, compared with ethylene glycol and alcohol Large amount, while the heat transfer efficiency decreases. Therefore, this antifreeze is less used. In order to reduce costs, many manufacturers mix ethylene glycol and diethylene glycol.

(3) Alcohol - water antifreeze

The boiling point of alcohol is 78.3°C and the freezing point is -114°C. Liquor and water can be mixed in any proportion to form antifreeze at different freezing points. The more alcohol, the lower the freezing point. Alcohol is flammable. When the alcohol content in the antifreeze reaches more than 40%, it is prone to produce alcohol vapor and catch fire. Therefore, the alcohol content in the antifreeze should not exceed 40%, and the freezing point should be limited to about -30°C. Alcohol-water antifreeze has the advantages of good fluidity, fast heat dissipation, convenient material extraction and simple preparation. Its disadvantage is that it is easy to catch fire, alcohol has a low boiling point and evaporation loss is high. After the alcohol evaporates, the composition of the antifreeze changes and the freezing point rises. Cars traveling in mountainous areas and highland areas should not use alcohol-water antifreeze because of the large evaporation loss of alcohol. In general areas, traffic should be regularly tested for alcohol content and supplemented in a timely manner.

3, role

Cooling effect :

Cooling is the basic role of coolant. A lot of heat is generated when the engine is working , and 60% of the heat is distributed to the surrounding space through the cooling system. Water and methanol coolants have a low boiling point and are boiled easily. If the vehicle is operating under coolant boiling conditions, engine damage and even paralysis can occur even in a short period of time.

Antiseptic effect :

Radiator, water pump, cylinder block and cylinder head, water distribution pipe and other components in the cooling system are composed of steel, cast iron, brass, copper, aluminum, soldering and soldering metals, etc., due to the different electrode potentials of different metals, the role of the electrolyte It is prone to electrochemical corrosion; at the same time, acidic products formed by the decomposition of diols in the cooling liquid and acid exhaust gas after combustion of the fuel may also penetrate into the cooling system and promote the corrosion of the cooling system. Corrosion in the cooling system will cause failure of the radiator tank, nozzle spacers, cooling pipes, joints, and water tank piping. Corrosion of the product will also cause dulling of the product, causing engine overheating and even squeaking. If the corrosion is perforated, the coolant will infiltrate the combustion. The chamber or crankcase can cause serious damage because when the coolant or water is mixed with the body oil, it generates oil and gum, weakens the lubrication, and causes the valve, the hydraulic valve stem, and the piston ring to stick. Therefore, a certain amount of anti-corrosion additives are added to the coolant to prevent corrosion in the cooling system.

Anti-scaling effect :

The scale in the cooling system is derived from calcium, magnesium and other cations in the water. These alkaline earth metal cations easily react with the ions in water to generate scale under thermal loading conditions. The scale can wear out the water pump seal and cover the outer wall of the cylinder block water jacket, which causes the thermal conductivity of the cylinder block to decrease, and the temperature in the high temperature zone of the cylinder head increases rapidly, causing cylinder cracking. Therefore, in order to reduce the formation of scale, the coolant needs to use softened deionized water during production and filling.

Antifreeze effect :

4, note

In addition to the selection of antifreeze, in the use of antifreeze, the majority of owners need to pay attention to the following aspects:

Note 1: Use the same brand of antifreeze as much as possible.

Different brands of antifreeze solutions may have different production formulas. If they are used in combination, chemical reactions may occur between various additives, causing the additives to fail;

Note 2: The effective period of antifreeze is more than two years (individual products are longer). When adding, it should be confirmed that the product is within the validity period;

Note 3: It must be replaced on a regular basis, usually for two years or once every 40,000 km, and taxis should be replaced.

When replacing, put the old liquid, clean the cooling system, and replace it with new liquid;

Note 4: Avoid using water.

The traditional inorganic antifreeze can not be used with water, it will produce precipitation, and seriously affect the normal function of antifreeze. Organic antifreeze can be used in water, but water cannot be exchanged too much.

In addition, since the antifreeze consists of mother liquor and soft water, there are many types of mother liquor such as tetraol. Ethanol, ethylene glycol, glycerin, etc. Soft water is water containing no or small amounts of calcium and magnesium ions, such as distilled water, uncontaminated rainwater, and snow water. When using antifreeze in the winter, increase the proportion of antifreeze medium line fluid. However, it is best not to exceed 60%. After all, the increase in mother liquor will reduce the cooling effect of the engine.

5, the most commonly used antifreeze - ethylene glycol antifreeze

According to the characteristics of antifreeze, most of the antifreeze liquids currently sold on the market are ethylene glycol-based products, and then add appropriate amounts of organic or inorganic salts to achieve anti-corrosion and rust prevention.

Second, the rapid detection of antifreeze

Measure the advantages and disadvantages of antifreeze are mainly the following two points: The first is the antifreeze effect, the freezing point of water is 0 °C, the general type of antifreeze can reach -40 °C, while the quality of antifreeze should be able to reach -60 °C, This is an important indicator for calibrating the quality of antifreeze; the other is the boiling point of antifreeze, the boiling point of water is 100°C, and the antifreeze should be at least above 108°C, ie the lower the freezing point and the higher the boiling point, the temperature difference among them. The larger, the better the antifreeze quality.

All countries have done a lot of research on this topic and have consistently introduced formula patents and excellent antifreeze products. The penetration rate of antifreeze in some advanced countries has reached 100%. The penetration rate of domestic antifreeze is low, and a considerable amount of commercially available antifreeze is imported. Because of the high price, it is generally used for imported vehicles. Although domestic antifreeze production has grown rapidly in recent years, many products lack stringent quality inspections and uniform inspection standards. To this end, we must absorb advanced foreign technology and combine China 's actual conditions to develop and produce highly functional antifreeze to meet the growing market demand.

According to the survey, more than 50% of global automotive engine failures originate from the cooling system! This shows the importance of a reasonable choice of antifreeze.

ATAGO antifreeze concentration meter provides a convenient and accurate rapid detection tool for manufacturers and vehicle owners to deploy different concentrations of antifreeze solution according to the demand of freezing point.

MASTER-BR Coolant Refractometer

This measurable concentration of ethylene glycol and propylene glycol and freezing temperature, this section has salt resistance and acid resistance.

Scale range

Ethylene glycol 0 to 70%, 0 to -50°C
Propylene glycol 0 to 70%, 0 to -50°C

PAL is a redesigned product of new and digital handheld instruments that will change the concept of traditional refractometers. PAL's product features are as follows: PAL's compact size will allow you to carry it anywhere, and it can be used both inside and outside the plant. This product is only one hundred grams weight and can be easily put into a pocket or hung on the neck or belt.

Simple measurement, easy to complete in 3 steps

Drop 2-3 drops of sample Press the START button to start Viewing the results

DR-A1 digital Abbe refractometer

Index of refraction (nD) Range: 1.3000 to 1.7100

Measurement accuracy: ±0.0002

Resolution: 0.0001

With simple operation, just set the refraction boundary line in the cross line, the refractometer can directly display the measured value (optional refractive index or sugar content%) and temperature. Without reading the analog scale, anyone can easily complete the measurement.

The refractive index has a linear relationship with the concentration of ethylene glycol and the freezing point.

It provides a reliable guarantee for the testing of raw materials for the manufacturer's ethylene glycol into the factory. The purity of the ethylene glycol is tested to provide a more accurate guarantee for subsequent preparation of various concentrations of ethylene glycol solutions. For example, the refractive index (20°C) for a 100% ethylene glycol concentration is 1.43100-1.43105. If the concentration is not pure, the refractive index will be low, and the purity of the ethylene glycol can be judged and the corresponding concentration can be found from the conversion table. freezing point.

RX-7000α automatic desktop digital refractometer

The RX-7000α is an upgraded version of the RX-5000α refractive index measurement range and measurement temperature, and has an electric heating module to maintain constant temperature. This product has a manual calibration function that can coordinate the different standard liquid values and measurement values measured by other refractometers.

The scale can be customized, and the linear relationship between the refractive index and the concentration of ethylene glycol can be set on the instrument. The measurement will be quick and easy. A button can be used to obtain the refractive index and concentration of ethylene glycol in a few seconds. It is a refractometer. Smart products in products.

At the same time, there is an automatic temperature control function, and the sample is controlled to the corresponding temperature for testing, and the result is more accurate.

Measuring range

Index of refraction (nD):
1.3250 to 1.7000
Brix: 0.00 to 100.0%
(ATC: 5 to 70°C)

Minimum display unit

Index of refraction (nD):
0.0001/0.00001 (Optional)
Brix: 0.1%/0.01% (optional)
Temperature: 0.01

Measurement accuracy

Index of refraction (nD): ± 0.0001
Brix: ± 0.1%

Repeatability

Index of refraction (nD): ±0.00005
Brix: ±0.02%

measure temperature

5 to 70°C

Measurement form

3 forms

Output terminal

• Printer (Digital Printer ATAGO)
• RS-232C

PRM-100α Online Refractometer

The high-precision online concentration meter PRM-100α consists of a detection unit (sensor) and a display unit. Compared with its predecessor, the PRM-85, it has a wider measuring range (Bixen 0.00 to 100.00%) and a higher accuracy (refractive index ± 0.00010, Brix). ±0.05), you can choose the smallest scale to display.
On the display system, the PRM-100α's color display makes it easier to read data, even at longer distances. This product can be widely used in the food, beverage, pharmaceutical and chemical industries. On-line refractometers can be used for dilution. The monitoring of the process, the mixing process and the concentration/moisture/mixing ratio of the final product can also be used to monitor the effectiveness of the online cleaning process.

This instrument can also customize the scale, directly used in the production pipeline detection of ethylene glycol concentration and the deployment of the concentration. Can display the refractive index and concentration of ethylene glycol.

Measuring range

Index of refraction (nD)
1.32000 to 1.55700
Brix
0.00 to 100.00%

Minimum display value

Index of refraction (nD)
0.0001 or 0.00001
Brix
0.1% or 0.01%(by selection)

Measurement accuracy

Index of refraction ±0.00010
Brix ±0.05%

measure temperature

5 to 100°C
(Clean-in-process (CIP) up to 130°C for no more than 30 minutes)

output method

RS-232C, DC4 to 20mA

power supply

AC 100 to 240V,
50 / 60Hz