Fundamentals of Electropolishing
You can define the electropolishing as a reverse plating procedure which has the characteristic of removing the outer surface of metal instead of depositing that metal in the surface. In order to achieve this, the part of the metal charged positive and submerged into a chemical bath (Wang et al., 2002). After this, the chemical applied for activating the procedure. The electric current in coordination with electrolyte pulls ions of metal off from the surface of that part leaving a shiny and smooth surface (Datta and Landolt, 2000). Similar to that of a snake shedding its skin, the defects over the surface are stripped out thereby revealing a new surface.
Applications of Electropolishing
According to (Landolt, Chauvyinger, 2003), electropolishing is applied in the following ways:
Improved resistance towards corrosion: through Electropolishing, corrosion resistance is improved as it removes imperfections from the surface which serve as initiation sites.
Deburring: Electropolishing eliminates performance-inhibiting surface burrs even from intricate and delicate parts.
Fatigue life improvement: Electropolishing removes micro-cracks as well as other defects on the surface over metal parts like twisting, flexing and bending springs before they can even compromise over performance.
Reducing discoloration: Electropolishing gives metals a bright and clean finish that lasts longer and helps metal parts retaining a new-like appearance.
Microfinishing: Removing oxides, chemicals, scale as well as surface irregularities. Moreover, Electropolishing improves the performance of parts and is the best solution for even those parts that cannot be treated by mechanical polishing or vibratory finishing.
How Electropolishing makes Parts Last Longer?
Since electropolishing removes all the imperfections from the metal part s surface, it makes them last longer. A very common imperfection is burred which are miniature pieces of displaced surface material that can either snag or break (Mohan et al., 2001). Other imperfections may include inclusions, retaining moisture where bacteria can grow. The fact is that uneven and rough surfaces, including those that cannot be seen without a standard microscope, tend to hinder electrical connectivity. Microscopic cracks are initiative sites from where parts can crack, bend or break prematurely. Electropolishing tends to remove all the imperfections thereby making parts to work better and last longer (Chatterjee, 2019).
Advantages and Disadvantages of Electropolishing
A wide range of materials is being used on a daily basis. Most of the metals possess their own utilities and properties. It is important that users understand these utilities and properties. The method of preserving metal, particularly steel, is referred to as Electropolishing. It is the electrochemical process which fines the uneven surface over metals and brings a natural shine and finishes to them (Rokosz, 2015).
Advantages of Electropolishing
- It removes the scratch and other abrasive marks that are over the surface of the metal.
- It brings a natural finish and shines to the metal.
- Electropolishing improves the smoothness level of the metal which also reduces the coefficient of friction over the surface. It helps to increase the metal life because of which it lasts longer than usual.
- Electropolishing process makes the metal corrosion-free.
- It removes the brittleness present on the metal.
Disadvantages of Electropolishing
- The process of electropolishing makes use of chemicals which can impose a long-lasting impact over the finished metal.
- To a certain extent, the roughness over the metal surface remains persistent and 100% smoothness is difficult to achieve.
- The cost of electropolishing procedure is somewhat higher and the process consumes a good amount of time as well.
Applications of Electropolishing
Electropolishing is a very versatile treatment and provides several benefits to individuals, companies, and organizations that are operating in different types of industries. Having a diverse range of applications, the process of electropolishing is a process to develop products of superior quality which would not be same without the metal finishing process (Bohinc et al., 2016). Some industries which benefit from the process of electropolishing include:
In this industry, electropolishing applied for improving the quality, longevity, and durability of many commonly used consumer goods. Examples of consumer goods include furniture, light fittings, and cookware. Nowadays, people are accessing products that are made from stainless steel alloys. It can be treated to improve hygiene level, facilitating maintenance and easy cleaning. As well as increased resistance towards wear and tear (Swain, 2010).
Medical And Dental Instruments:
Electropolishing is a single-use treatment which used for producing hygienic, clean and biocompatible medical and dental instruments. Many times, this is also in use for precision utensils, this process is an alternative to passivation for creating pristine and polished surfaces that are also resistant towards bacterial growth. Electropolishing plays a very important role in the medical and dental industries and is commonly in use for the production of needles and scalpels (Rokicki et al., 2015).
Car Parts And Accessories:
Removing of debris from the outermost surface of metal parts and accessories and delivers several benefits to consumers and manufacturers. Electropolishing will enhance the life of the automobile and HGV parts along with reducing the risk of corrosion (Kim et al., 2016).
Aircraft Metal Parts:
Aerospace metal parts and electropolishing go side by side. Since electropolishing is capable of deburring metal parts. Also, providing the smoothest finishing and maximum precision. The electropolishing technique is applicable to produce aircraft metal parts for the aerospace and defense industries. It makes the part resistant and streamlined to friction and corrosion. This technique of metal finishing also reduces the risk of fatigue resulting in prolonged life of parts that are in use even in the most stressed environment (Lochy et al., 2018).
Food And Beverage:
Electropolishing provides preventative measure within the food and beverage industry. In the preparation of food and drinks, hygiene is very crucial. The metal treatment is widely applicable for removing contaminants and residues that can present a danger for human health (Tian et al., 2008).
Household And Electrical Items:
Most of the appliances, machines, and gadgets are taking power from electricity. The electropolishing can provide various benefits in the development of fabrication of these electrical goods. This procedure improves conductivity performance of products by removing imperfections which hampers productivity through the generation of resistance (ASME, 2005).
Quality Control on Electropolishing
The degree to which the quality control of electropolishing evaluated is the determination of the consistency and fine quality of the finish. Several electropolishing shops are employing a minimum number of control or no controls at all. Where there is a lack of quality control, the quality is unpredictable and inconsistent. There are certain areas that are functions of technology whereas; others may fall within the aspect of electropolishing (Arnold et al, 2004).
It is very important that apply proper electrolyte. Precisely maintain temperature along with regular monitoring as well. Critical factors within the chemistry are the particular gravity which is an indication of water content. As well as a major determinant of hydroscopic electrolytes, metals content, and acid concentration. A supply of ripple-free and clean DC power should be available for driving the process along with adequately sized cables and connectors to cathodes and anodes. Moreover, the DC voltage needs the application at the appropriate voltage and the current density (ASTM, 2001).
For most products, mirror-like luster is a major aim. On the other side, it may involve additional technical and functional benefits of electropolishing where no possibility through mechanical processes. Since there is no mechanical disturbance of the service in the process of metal removal, the electropolished surface possesses true grain structure and properties of the bulk metal (Hammond et al., 2012).
On the other side, the mechanical polishing process leaves a layer of the disturbed structure. Mechanically fitted surfaces will not include reported properties that are for bulk metal irrespective of the thickness of the disturbed surface of a mechanical process that employed (Hubbard-HalInc.Inc 2019).
Recent Developments in Electropolishing
Surface finishing and metal polishing are very important for determining the durability against corrosion and longer life of metal parts. Nonetheless, both the clients and the polishing company has a pressing need to occasional remainder to maintain the relationship. It is between the quality of finish of the metal surface as well as its capability to resist corrosion and rust (Han and Feng, 2019).
Although, previously it was very customary to polish metal parts that were in use as external architectural features. Now, since various studies conducted and proved. That quality electropolishing not only enhances the appearance of metal parts and its surfaces but also helps in increasing their durability. For example, an industry where they use stainless steel, electropolishing is its integral component (Hensel, 2000).
Electropolishing Latest Trend:
When metal parts undergo basic polishing, there are corrugations over the surface of the metal at the end of the process. Such grooves can potentially house several chloride ions which help to remove at passivation resulting in rusting and corrosion within a very small time duration. Industries where hygiene and appearance are inferior. This situation can bring in huge financial losses. So, it requires to replace metal at frequent levels. It can be said that the resistance metal surfaces which have been treated with mechanical or any other type of old-fashioned polishing are not an effective solution for making the metal rust and corrosion-proof (Zuzel and Wójcik, 2012).
Experts try to update the metal polishing standards regularly updated. The time, when a technological advancement allows it. As well as when the conventional methods of polishing fail in delivering the desired results. For example, the basic polishing of metal performed in different industries since the 1980s. It was mostly applicable in the interior designing sector. The furniture industries using this technique for bringing in a high-gloss look to give a luxurious appearance. Although, it discovered very soon that the shiny gloss alone is not enough way to protect the surface from corroding or wearing down (Datta and Landolt, 2000).
New and improved ways to polish the surface of metals are being usually derived from the current methods. It is a part of the process to continuously strive for better results (Landolt, Chauvy and Zinger, 2003).
Although the application has spread over many industries, they usually fall within four categories which are:
With its proper application, electropolishing dissolves metal from the edges in a more rapid way than that of flat surfaces. The current density of this process is similar to the plating. As electropolishing is in practice for removing surface metal, it helps in reducing or removing burrs. Additionally, parts with critical final dimensions that require deburring should accommodate metal removal. A good electropolisher will provide appropriate AQL data which will show dimensions that are within tolerance and that there is a good handle over process parameters (Wang et al., 2002).
As current density serves to be an advantage over edges and burrs. You can use similar physic over flat surfaces as well. When you try to remove metal from the surface. The removal takes place at higher points over the surface and less on lower points. Developments within medical, hydraulic, automotive as well as other components which require smooth surface are benefiting from the smoothing aspect of electropolishing (Christophersen et al., 2003).
Several industries have moved on from harsh chemical environments for their stainless components. There are some stainless alloys that tuned due to environments. Where corrosion is high, most of the time metal requires the need to either meet or exceed corrosion standards for field use. Those engineers who are willing to improve corrosion resistance. There filed test standards provide or salt spray/fog tests per ASTM B-117. Vendors of electropolishing should be able to extend assistance in determining corrosion test parameters for particular industries (Lee and Lai, 2003).
Controlling the Size
Experienced electropolishing practitioners have the potential to save plenty of parts from the scrap bin. When a part if oversized, it will be fabricated from a thicker material than was specified or it will grow in dimension from the heating process (Kao and Hocheng, 2003).
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