CN-121978169-A - Quantitative evaluation method for uniformity of conductive coating on steel surface based on SKP potential variation coefficient

Abstract

The invention relates to the technical field of quantitative evaluation of quality of conductive coatings on surfaces of materials, in particular to a quantitative evaluation method of uniformity of conductive coatings on surfaces of steel based on SKP potential variation coefficients. The method comprises the steps of firstly cleaning the surface of a coating sample to be tested, planning at least 30 detection points in a system, then carrying out non-contact scanning by using a Scanning Kelvin Probe (SKP) to obtain the surface potential values of each point, then calculating the ratio of the standard deviation to the average value of all the potential values to obtain a potential variation coefficient epsilon, and finally carrying out objective quantitative grading on the uniformity of the conductive coating according to a preset epsilon value grading standard. The invention converts the traditional subjective and qualitative uniformity evaluation into objective and quantitative analysis, has the advantages of high detection efficiency, no damage, accurate positioning of the defect area and wide applicable conductive coating types, and provides reliable basis for conductive coating process optimization and product quality control.

Inventors

• LI LIN
• WANG TING
• CHEN YIQING
• ZHONG BIN
• AI FANGFANG
• GAO PENG
• SAN HONGYU
• Sha Kaizhi
• SU XIANDONG
• YU ZIHAN

Assignees

• 鞍钢股份有限公司

Dates

Publication Date

20260505

Application Date

20260112

Claims (5)

1. 1. The quantitative evaluation method for the uniformity of the conductive coating on the steel surface based on the SKP potential variation coefficient is characterized by comprising the following steps of: 1) Sample preparation, namely selecting a sample of the conductive coating of the steel to be tested, and carrying out surface cleaning treatment; 2) Setting at least 30 detection points on the surface of the sample; 3) Potential scanning, namely scanning at the detection points by using a Scanning Kelvin Probe (SKP) system, and measuring and obtaining the surface potential value E i of each detection point; 4) And (3) carrying out uniformity quantification calculation, namely calculating a potential variation coefficient epsilon of the surface of the sample based on the surface potential values E i of all detection points, wherein the potential variation coefficient epsilon is calculated according to the following formula: ×100% s is the standard deviation of the potential values of all detection points; The average value of the potential values of all detection points is obtained; the calculation formula of S is as follows: wherein n is the total number of detection points, and n is more than or equal to 30; 5) Evaluating the uniformity grade of the conductive coating on the surface of the steel material according to the numerical value of the potential variation coefficient epsilon; When epsilon is less than or equal to 5%, the uniformity of the conductive coating is evaluated to be excellent; when 5% < ε≤10%, the uniformity of the conductive coating was evaluated as good; When 10% < ε≤20%, the uniformity of the conductive coating was rated as normal; when ε >20%, the conductive coating was evaluated as having poor uniformity.
2. 2. The quantitative evaluation method for the uniformity of the conductive coating on the steel surface based on the SKP potential variation coefficient according to claim 1, wherein in the step 1), the surface cleaning treatment is degreasing treatment.
3. 3. The quantitative evaluation method for the uniformity of the conductive coating on the steel surface based on the SKP potential variation coefficient according to claim 1 is characterized in that in the step 2), rectangular grids are used for dividing detection points into pieces of 5-10 mm in grid spacing for samples with regular shapes, and polar coordinates or even distribution principles with the center of the samples as an origin are used for planning detection points for samples with irregular shapes.
4. 4. The quantitative evaluation method for the uniformity of the conductive coating on the steel surface based on the SKP potential variation coefficient according to claim 1, wherein in the step 3), the diameter of the probe of the scanning Kelvin probe is 150 μm or 500 μm, the distance between the probe and the surface of the sample is controlled to be 30-100 μm, and the steps in the transverse and longitudinal directions of scanning are all 10-40 μm/point.
5. 5. The quantitative evaluation method for the uniformity of the conductive coating on the steel surface based on the SKP potential variation coefficient according to claim 1, wherein in the step 3), further comprises performing detection point encryption measurement on a preset defect area or edge area of the sample surface, and taking part of the data into calculation in the step 4).

Description

Quantitative evaluation method for uniformity of conductive coating on steel surface based on SKP potential variation coefficient Technical Field The invention relates to the technical field of quantitative evaluation of quality of conductive coatings on surfaces of materials, in particular to a quantitative evaluation method of uniformity of conductive coatings on surfaces of steel based on SKP potential variation coefficients. Background The steel surface coating is a key technology for improving the corrosion resistance, the decoration and the service life. The uniformity of the coating refers to the uniformity of the coating in terms of thickness, chemical composition and microstructure, and directly determines the barrier protection effect, adhesion and reliability of the final product of the coating. If the uniformity is poor, the area with over-thin part becomes a rapid channel for penetration of corrosive medium, so that the base material is corroded early, and the area with over-thick part possibly causes the appearance defects of increased internal stress, reduced adhesive force or sagging, orange peel and the like of the coating. Therefore, the method for accurately and efficiently evaluating the uniformity of the coating is a core link for controlling the quality of the product and optimizing the process parameters. At present, the conventional method for evaluating the uniformity of the coating on the surface of the steel plate in the industry mainly depends on physical thickness measurement or local component analysis, has limitations generally, and is difficult to realize rapid and quantitative comprehensive evaluation on the overall uniformity of the coating. Specifically: 1. Visual inspection and observation by an optical microscope, the method is most direct, and obvious macroscopic defects such as coating leakage, bubbles, wrinkles and the like can be found. However, the results are highly dependent on the experience of operators, have strong subjectivity, cannot identify microscopic thickness variation, microcracks and gradient distribution of chemical components, belong to qualitative or semi-qualitative evaluation, and have poor repeatability and comparability. 2. The single-point thickness measuring method, such as magnetic thickness measuring method and eddy current thickness measuring method, can accurately measure the thickness of the coating at a certain point and is simple and convenient to operate. However, the method can only provide data of discrete points, the number of sampling points is limited, the position selection has randomness, the continuous distribution condition of the coating on the whole surface can not be comprehensively reflected, a local uneven area is easily omitted, and the overall attribute of uniformity is difficult to make quantitative judgment. 3. Destructive cross-section analysis by cutting a sample, preparing a polished cross-section, and observing and measuring using a metallographic microscope or a scanning electron microscope. Although the method can obtain accurate information of coating thickness, interface combination and microstructure, the sample preparation process is complex and time-consuming, and causes permanent damage to the sample, and is not suitable for online detection, mass screening or nondestructive evaluation of finished products. 4. Component distribution analysis techniques such as X-ray fluorescence spectroscopy or electron probe microscopy can analyze the two-dimensional distribution of elements in the coating. However, these devices are generally expensive, insensitive to light elemental analysis, and have slow measurement speeds, complex data interpretation, and more focused on qualitative or semi-quantitative distribution of chemical components, rather than directly and comprehensively characterizing the "functional uniformity" directly related to the protective properties of the coating. In recent years, scanning kelvin probe technology has been tried to study the starting point of metal corrosion under conductive coatings, defects of conductive coatings and failure process due to its non-contact, non-destructive, high spatial resolution characteristics. The technology can sensitively reflect the difference of microscopic electrochemical states of the conductive coating/metal interface by measuring the local work function (related to corrosion potential) of the material surface. However, in the existing researches, SKP technology is mostly used for qualitatively observing potential distribution images, or for carrying out mechanism analysis aiming at specific defect points, a systematic method is not formed yet, and massive potential data obtained by SKP scanning is converted into a concise, objective and comparable quantization index for rapid grading and quality evaluation of the overall uniformity of the conductive coating. In summary, the prior art lacks an effective means for performing objective grading evaluation o