How to Control Color Difference for Automotive Paint Coating

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2019-10-16

How to Control Color Difference for Automotive Paint Coating

  During the painting process of car bodies, it is difficult to control the color difference of the topcoat, and the general requirement for the color difference of the topcoat is △ E ≤ 2.0. 

There are two main methods for measuring color difference: one is visual inspection, which is to visually inspect with the eyes; The second is to use a colorimeter for measurement. 

Artificial visual evaluation, due to many influencing factors and the difficulty of presenting detection results in numerical form, 

can use professional color detection instruments, currently commonly used is color difference meters.

  A colorimeter is a precision color detection instrument that can measure x, y, and Y on a sample, namely the chromaticity coordinates and brightness factor. 

The chromaticity chart can then determine the position of the measured color on the chromaticity chart. 

In order to make the color space more in line with visual observation of color differences, x, y, and Y are transformed into a *, b *, and L * values through a series of transformations, 

where the size of a * value represents the red green phase (positive value is red), b * value represents the yellow blue phase (positive value is yellow), and L * value represents brightness, that is, black and white phase (0 is black, 100 is white). 

In this way, each color displays a corresponding set of a *, b * L * values, and two different colors display different a *, b *, and L * values, thus obtaining Δ A Δ B Δ L. 

The total color difference between the two can be calculated by the difference in chromaticity and brightness Δ E table. 

The colorimeter can print out the a *, b *, and L * data of two colors and directly print them through a computer system Δ E value, also known as color difference.

  Measure the car topcoat sample using a colorimeter and compare it with the pre measured standard topcoat color sample. The instrument can display the color difference measurement results. 

By measuring the range of color difference values, users can evaluate whether the color of automotive topcoat samples is qualified, thereby controlling the appearance color quality of automotive topcoat spraying.