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[YesAuto Use Car Collection] Second-hand cars are different from new cars. Each car has different conditions in actual use. The condition of the car cannot be standardized like a new car. Therefore, when buying and selling second-hand cars, the vehicle will be inspected in an all-round way. The final price of the vehicle is measured by the results of the test. Friends who have some knowledge of the second-hand car industry must know that every inspection master will use the help of a paint film meter when inspecting vehicles. It is as important as a soldier's gun to a second-hand car inspector. Not much nonsense, today I teach you how to use the paint film meter, so that you can really know what you are in the process of actually buying a second-hand car.


1. The paint film meter is an auxiliary tool and cannot be the only basis for judging whether there is spray paint or sheet metal on the paint surface, because some people will add iron powder to the paint or putty in order to conceal the true condition of the vehicle. In this case, paint The membrane meter cannot measure the problem . Although the probability of occurrence of the above-mentioned problems is relatively small, you are not afraid of ten thousand just in case.

2. For most of us, the paint film meter has fewer application scenarios and the price is not cheap, so it is not recommended for everyone to buy it. We only need to understand how to use it, and ask the merchant to borrow one when preparing to buy a second-hand car. .

3. As a professional measuring instrument, the accuracy of the paint film meter is very high, but there may still be errors. Therefore, when we actually measure, we should take as many points as possible for a body part, which can effectively ensure the accuracy of our measurement.

Introduction of paint film meter:

The scientific name of the paint film meter is a coating thickness gauge, which is a professional instrument used to detect the thickness of a coating. In the automotive industry, the paint film meter mainly detects the thickness of the paint surface of the car without damage, so as to judge whether the paint surface of the vehicle has been repainted. At present, most of the vehicles on the market are made of cast iron/steel, aluminum and carbon fiber materials. We can simply understand them as iron, aluminum, and carbon fiber materials. The paint film meter can detect the first two materials, which is Speaking of carbon fiber materials, there are also vehicle plastic parts (such as front and rear bumpers) that do not work.

Fe: Fe in the paint film meter means that the measurement is made of ferromagnetic metal substrates, and the principle of magnetic thickness measurement is adopted. It is used to measure the thickness of non-magnetic coatings such as paint, varnish, enamel, chromium, galvanized, etc. on ferromagnetic substrates such as steel.

NFe: The paint film meter NFe indicates that it is measuring non-magnetic metal substrates, and adopts the principle of eddy current thickness measurement. It is used to measure non-conductive coatings on non-magnetic metal substrates such as copper, aluminum, die-cast zinc, brass, etc., such as paint and anodizing. Coating thickness of layers or ceramics, etc.

Fe/NFe: At present, most of the paint film meters on the market use iron-aluminum dual-purpose probes. The principle is to combine the principle of magnetic measurement and eddy current measurement. It can automatically identify the measured substrate, so the operation is simpler. , No need to manually select the measurement material.

μm (micrometer): Micrometer, a unit of length, symbol: μm, pronunciation: miu. One micron is equivalent to one thousandth of a millimeter.

mil (mil): mil is both an angle unit and a length unit. Angle unit (closed position): 1mil=0.06° 360°=6000mil Length unit (melt): 1mil=0.025mm.

Generally, the measurement unit of the paint film meter is μm (micrometer) and mil (mil). Among them, the micrometer is the most widely used in the car ring, and all the measurement data are also in micrometers.

●Practical use of paint film meter:

After understanding the detectable materials and measurement units of the paint film meter, we have basically mastered its use. Next, we will take actual measurements as examples to facilitate your understanding.

Generally, the original paint surface thickness of the vehicle is about 100-180 microns, but because of the differences between car brands and models, the paint surface thickness will be different, so in general, the paint surface of the roof is used as the test The benchmark value of the paint surface, because the probability of roof spraying is very low, the value is more accurate than other positions.

After obtaining the accurate value of the roof, it can be used as a basis for measuring whether the paint on other parts of the car body is painted or not. The front machine cover, fenders (front, rear, left, and right), doors, ABC pillars, and trunk can be measured successively.

There are more accidents of vehicle collisions or rear-end collisions, so the inspection of the engine compartment cover must not be careless. The average value of the cabin cover detected by the paint film meter is 260 microns, which shows that the front cabin cover of the car must have been painted.

The measurement of the fender includes four parts, front, rear, left, and right. Because of the large coverage area and unevenness, the paint surface and the paint film meter are difficult to form 90 degrees, so it is recommended that you take as many points as possible during the measurement, so as to effectively ensure We measure the accuracy of the values.

The trunk is the same as the cabin cover. There are more rear-end collision accidents. If we find that the trunk is painted or sheet metal during the measurement, we need to check whether the rear anti-collision beam is damaged, so as to judge the severity of the accident.

The paint surface of the car door is an important basis for judging whether the vehicle has a side collision. However, considering that the door may be bumped with the car next to it when the door is opened or closed, the probability of repainting is relatively high. Therefore, if you find that the door is painted seriously, you must apply the ABC column Check carefully, and then analyze the cause of the spray paint.

The detection of A, B, and C pillars is an important basis for judging whether the vehicle is an accident vehicle. If there are traces of sheet metal or spray paint repair on the A, B, and C pillars, it indicates that the vehicle may have a serious traffic accident, and the vehicle needs to be further inspected. Chassis, and front and rear side members to determine the severity of the accident.

We compare the reference value in the actual measurement, it is easy to judge whether the vehicle has spray paint, but if the measured value is several times the reference value, or even reaches more than 1,000 microns, it can basically be concluded that there is sheet metal in this part, because as long as the sheet metal repair is performed Need to scrape putty leveling, so the value must be much higher than spray paint.

Full text summary:

In fact, the paint surface best reflects the real condition of the vehicle. As long as a collision occurs, it will definitely cause damage to the paint surface. Therefore, if we find that the vehicle is painted or sheet metal during the inspection, we only need to follow the vine to check the damage degree of the vehicle, and then analyze The cause of the accident is sufficient. (Part of the picture comes from the network article/Car Home Zhao Xiang)