What is an electrogram and what is it for? -Engineering clicks (2023)

• November 16, 2019
• engineering click

Electropolishing is a material removal process that uses an electrochemical process called electrolysis. During this process, the amount of material removed is very small as it is only used for polishing. A negatively charged copper electrode and a positively charged workpiece are immersed in a fast-flowing electrolyte solution. When connected to battery power, the tabletop begins to dissolve into the solution.

the process of electrolysis

The electropolishing process involves the removal of material by diffusion from the workpiece into an electrolyte solution. The required information is as follows:

• Tanks with different acid-based electrolytes (the choice of acid depends on the material being polished)
• Copper cathode
• The workpiece acts as a riser in the system.

The power supply is usually direct current. The negative pole is connected to two or more copper cathodes, and the positive pole is connected to the workpiece. At this point, the workpiece is surrounded by copper cathodes. The system also includes a heating system, since the electrolyte must have a high constant temperature. There is also a pump or stirrer that moves the electrolyte during the process.

Materials that diffuse during this process are not deposited on the cathode. It only remains in the electrolyte solution - suitable mud tanks and filtration are also part of the system. The mud tank receives input from the main tank and the suction pump forces the liquid through the filter. After filtering, the liquid goes to a heat exchanger where it is reheated before re-entering the system. Since the process is controlled by direct current, the amount of material removed depends on the strength of the current.

The figure below shows the relationship between current and anode potential. Between the area from zero to A the workpiece can only be smoothed, while between B and C the polishing process takes place.

Application of galvanization

• This process is often used as a pre-treatment for electroplating to achieve good adhesion
• Electroplating is widely used in high-quality lounge chairs, tables and waste bins
• For polishing very sensitive and small instruments, including surgical instruments, medical instruments and food processing equipment
• This process is also used to deburr small tools and instruments that cannot be removed by hand grinding/traditional tools
• Electropolishing is also a common post-treatment for many products deformed by processes such as nitriding, annealing, welding, brazing and carburizing.
• The process can also be used to increase the reflectivity of the product's outer surface
• This is perfect when you want to remove stress/unwanted hardened layers from the product material - it also extends the life of the product
• Micromachining of metals and different alloys

Material

Any material that can conduct electricity can benefit from this process. Some common materials are:

• iron
• nickel alloy
• copper alloy
• Titanium alloy

Guidelines for Mechanical Design

• Electropolishing affects geometric features, such as sharp corners, which do not remain sharp after machining. There are limitations such as a radius of approximately 0.05 mm and an aperture size of approximately 0.1 mm in diameter. Note that the holes will not remain straight or perfect after this process
• With a wall roughness of approximately 0.2 to 12.5 microns, excellent surface conditions can be achieved with this process. Achievable tolerance limits are from a minimum of 0.013 mm to a maximum of 0.5 mm, depending on how long the process takes

Changes in the electrolysis process

The electropolishing process is basically controlled by seven different parameters that directly affect the result. These parameters are as follows:

• Workpiece material
• Condition of the workpiece surface
• Applied current density
• initial surface roughness
• Apply tension to the entire workpiece
• The type and nature of the acid used
• Electrolyte temperature during the process

There are some specific acids that can be used for specific materials polished with this process. Current and voltage densities will adjust according to surface conditions.

the economy of the process

• Due to the moderate productivity of the electropolishing process, it is very economical for small to medium series production. However, in some cases high yields can be achieved to some extent
• Typical removal rates using this process are approximately 50 to 250 cubic meters per second with a linear penetration rate of 0.15 mm per second
• Their use is often limited to high-value products due to high energy consumption during processing
• The process has a short installation time but low hardware utilization
• Electrolytes can be hazardous to the environment if not disposed of properly
• The entire process can be easily automated to facilitate the use of potentially hazardous acids
• Equipment costs are very high, but labor costs are low to moderate - depending on complexity

Advantages of electropolishing

• The electropolishing process can be used to process multiple products simultaneously
• or more quantities of the same product
• The process can be safely used on materials sensitive to heat damage
• Excellent replacement for all parts damaged by heat treatment
• This process can polish very complex shapes - often to a level of complexity that cannot be polished by any other process

Disadvantages of electropolishing

• Electropolishing does not remove surface defects such as seams or non-metallic inclusions in metal parts
• This process will not work if the part is composed of more than two alloys (multiphase alloys), one of which does not support anodic diffusion
• The electropolishing process cannot remove rough scratches on the surface of the component
• Products containing high levels of silicon, sulfur and lead can be irritating
• Electropolishing removes small scratches, but does not work well on wavy surfaces
• This process is highly dependent on the state of the parent metal