Introduction: Electroplating can give various metal and non-metal devices with excellent appearance and good corrosion resistance and wear resistance. It can also make the surface of the device obtain a variety of special functions, making it a new type of functional material. Therefore, electroplating It has been widely used in various industrial production departments. The ten performance tests of electroplating are shared below, and the content is for your reference:
Electroplating is the process of plating a thin layer of other metals or alloys on the surface of certain metals using the principle of electrolysis. It is the process of using electrolysis to attach a metal film to the surface of a metal or other material to prevent metal oxidation ( Such as rust), improve wear resistance, electrical conductivity, reflectivity, corrosion resistance (corrosion-resistant metal is mostly used for coating metal) and enhance aesthetics.
The appearance inspection of the electroplating layer of metal parts is the most basic and commonly used inspection. The plating parts with unqualified appearance do not need to be tested for other items. Observe visually during the inspection, and according to the appearance, the plated parts can be divided into three categories: qualified, defective and scrap. Poor appearance includes pinholes, pitting, nodules, peeling, blistering, shedding, yin and yang, spots, scorching, shadows, dendritic and spongy river deposits, and parts that should be plated but not plated, etc. defect.
1) Surface roughness test
Surface roughness measurement belongs to the measurement of microscopic length. At present, there are many methods such as comparison method, optical method, needle drawing method, etc. The profilometer method in the needle drawing method has the advantages of small size, light weight, high magnification, and fast measurement speed. widely used.
2) Coating brightness
The brightness of the coating is an indicator measured by the plating parts with higher decorative requirements. The brightness refers to the ratio and intensity of the reflected light on the surface of the coating under the action of a certain illuminance and angle of incident light, usually by visual inspection and sample comparison Evaluate the brightness of the plated parts. For flat plated parts, using a photometer can get very good results.
Adhesion strength test
The adhesion strength of the coating is also called the adhesion of the coating. It refers to the adhesion of the coating to the substrate or intermediate coating. The adhesion of the coating has a direct impact on the decorative performance and protection. It is one of the important inspection indicators for the quality of the metal coating. One.
Choice of Test Method for Adhesion Strength of Metallic Coating
The thickness of the plating layer and its uniformity are important signs of the quality of the plating layer, which greatly affects the reliability and service life of the product. The thickness measurement methods of the electroplated layer are divided into two categories: destructive measurement and non-destructive measurement. Destructive measurement methods include: chronograph flow method, spot thickness measurement, coulomb method, metallographic method, etc.; non-destructive measurement methods include: magnetic method, eddy current method, β-ray backscattering method, X-ray spectroscopy, etc.
Thickness test methods and corresponding standards
The porosity of the coating refers to the size of the small pores from the surface of the coating to the base metal that affects the protective ability of the coating. Methods of measuring pores include sticking filter method, dipping method, electro-coating method, gas permeation method and so on.
Coating porosity test method
Hardness is one of the important mechanical properties of the coating. The hardness of the coating is determined by the crystalline structure of the coating metal of the nozzle. In order to eliminate the influence of the base material on the coating and the coating thickness limits the size of the indentation, the microhardness method is generally used. Hardness test reference standards: GB/T 9790, ISO 4516, ASTM B578.
Vickers/Knoop Hardness Tester (INNOVATEST, Netherlands)
Vickers hardness indentation (left) and Knoop hardness indentation (right)
Vickers hardness calculation formula:
P — test force, kg;
d — The average length of two diagonal lines, mm.
Knoop hardness calculation formula:
F — Test force, N;
d — The length of the diagonal of the indentation, mm.
Internal stress test
The internal stress of the coating refers to a kind of equilibrium stress in the coating under the condition of no external load. This kind of stress is affected by some deposition factors during the electroplating process, causing metal lattice defects. Certain metal ions, anions and organic additives in the plating solution will significantly increase the internal stress of the plating. The internal stress of the coating can cause bubbles, cracks, and peeling of the coating during storage and use. When external forces are applied, it can also cause stress corrosion and reduce fatigue strength. The methods for measuring the internal stress of the coating include: bending cathode method, rigid flat belt method, spiral shrinkage tester method, etc. The test method can refer to ASTM B636.
Hydrogen embrittlement and ductility test
The brittleness of the coating is an important indicator of the physical properties of the coating. The presence of brittleness often leads to cracking of the coating, a decrease in bonding force, and even a direct impact on the use value. The brittleness test of the coating generally involves deforming the sample under the action of external force until the coating cracks, and then the degree of deformation or deflection value when the coating cracks is used as the basis for evaluating the brittleness of the coating. The test can refer to the standard ASTM F519.
The ductility of the coating refers to the ability of the coating to not break or crack when it undergoes plastic deformation or elastic deformation under the action of external force, or when both types of deformation occur at the same time. The methods to determine the brittleness of the coating include delayed failure test, slow bending test, stress ring test, etc.; methods to determine the toughness of the coating include tensile test and bending test. The standards that can be referred to are: GB/T 15821, ASTM B489, ASTM B490 .
The solderability of the plating layer refers to the ease with which the solder flows on the surface of the metal to be soldered, that is, the ability of the plating layer to be wetted by the molten solder. Different coatings have different ability to be wetted by the same molten solder; even the same coating has different brazing properties due to different impurity content and coating structure. Therefore, the solderability of the plating layer can be tested to better understand the matching between the plating layer and the solder, so that the solder can be selected in a targeted manner to meet the needs of the electronic process for the solderability plating layer. The solderability test methods mainly include slot welding method, ball welding method, and wet weighing method. Refer to the standard GB/T 16745, ASTM B678.
Corrosion resistance test
Corrosion resistance refers to the ability of electroplated products to resist corrosion under environmental conditions, and it is one of the important performance indicators of the coating. Whether it is a protective coating, a decorative coating, or a functional coating, there are strict requirements on the corrosion resistance of the coating in a certain environment. Because once the coating is corroded, the product cannot perform its due function. The corrosion resistance test is an important means to evaluate the performance of the coating and evaluate the service life of the product. It is of great significance to ensure the safe use of the product.
Coating corrosion resistance test method
Some coatings are used in frictional parts and need good wear resistance. It is generally believed that the hardness of the coating is high and the corresponding wear resistance is good. Therefore, sometimes people use the hardness of the coating to compare the level of wear resistance. This method is not very scientific. Because the wear resistance of the coating depends not only on the hardness, but also on the friction of the material and the surface of the object, the load during friction, the lubrication state, and the temperature. Therefore, the wear resistance test of the coating is mostly to simulate the actual use situation and do abrasion test. The test equipment is an abrasion tester, the standards that can be referred to are: GB/T 12967, ASTM F1978.