1. Mechanical polishing: polishing on a special polishing machine. Mechanical polishing is mainly divided into two steps: rough polishing and fine polishing.

      Rough polishing: The purpose is to remove the polished deformation layer.

      In the past, the commonly used abrasives for rough polishing were α-Al2O3, Cr2O3 or Fe2O3 with a particle size of 10-20μm, which was used to form a suspension by adding water. At present, artificial diamond abrasives have gradually replaced abrasives such as alumina because of the following advantages:

      1) Compared with alumina, diamond abrasive grains with much smaller particle size have a much higher polishing rate. For example, the polishing rate of 4~8μm diamond abrasive grains is similar to that of 10~20μm alumina or silicon carbide;

      2) The surface deformation layer is shallow;

      3) Polishing quality is excellent.

       Fine polishing: Also known as final polishing, the purpose is to remove the deformed layer produced by rough polishing and reduce polishing damage to a minimum. The commonly used fine polishing abrasives are MgO and γ-Al2O3, of which MgO has the best polishing effect, but the polishing efficiency is low and difficult to master; γ-Al2O3 has a high polishing rate and is easy to master.

2. Electrolytic polishing: a polishing method that uses anodic etching to make the surface of the sample smooth and bright.

       Electrolytic polishing uses stainless steel as the cathode, the polished sample as the anode, and the container holds the electrolyte. When the current is turned on, the metal ions of the sample are dissolved in the solution. Under certain electrolysis conditions, the surface of the sample is slightly microscopic. The dissolution of the convex part is faster than that of the concave part, thereby gradually making the surface of the sample rough and smooth.

Advantages and disadvantages:

      1: Compared with mechanical polishing, electrolytic polishing is a purely electrochemical dissolution process, without the effect of mechanical force, and does not cause surface deformation of the metal.

      2: This method should be used for single-phase alloys with low hardness and aluminum alloys, magnesium alloys, copper alloys, titanium alloys, and stainless steels that are difficult to achieve by general mechanical polishing.

      3: Electrolytic polishing has low requirements on the degree of polishing of the sample (generally, it can be smoothed with No. 800 water sandpaper), with fast speed and high efficiency.

      4: Electrolytic polishing is particularly sensitive to the inhomogeneity of material chemical composition and microsegregation, and non-metallic inclusions will be severely corroded, so it is not suitable for metal materials with serious segregation and metallographic samples for inclusion inspection.

      Matters needing attention: Electrolytic polishing must select a suitable voltage and control the current density. Too low and too high voltage cannot achieve the purpose of normal polishing.

3. Chemical polishing: use chemical dissolution to obtain a smooth polished surface.

      Immerse the sample in the chemical polishing solution, perform appropriate agitation or wipe with cotton, and after a period of time, a bright surface can be obtained. Chemical polishing has the function of chemical corrosion and can display the metallographic structure. After polishing, it can be directly observed under the microscope.

      Chemical polishing is simple in operation, low in cost, does not require special equipment, and does not require high surface finish on the original sample.

      The composition of chemical polishing liquids varies with polishing materials. Usually mixed acid. Commonly used acids are: orthophosphoric acid, chromic acid, sulfuric acid, acetic acid, nitric acid and hydrogen acid; in order to increase the activity of the metal surface to facilitate chemical polishing, a certain amount of hydrogen peroxide is also added. After the chemical polishing solution is used, the metal ions in the solution increase, and the polishing effect is weakened, so it needs to be replaced frequently.

Hongchang stainless steel surface treatment material research and development and production, stainless steel pickling passivation paste, stainless steel passivation solution, stainless steel electrolytic polishing solution, copper pickling solution, stainless steel pickling passivation solution, stainless steel pickling passivation agent, Tel: 0550- 7093728 Mobile: 18175233777 15212005511 Contact: Miss Yang