Rust and stain-free finished metals are present in numerous objects we use. Washing machine drums, surgical devices, knives and any metallic object that has to be free of deformation, corrosion and minute tears needs to be cleaned and polished to achieve a pristine state. Electropolishing is one such method that smoothes and streamlines metal surfaces.
Milling, blasting and buffing are a few of the traditional mechanical techniques to polish metal. However, embedded abrasives and compounds are difficult to remove despite using high-end machines. Electropolishing, on the other hand, makes lighter work and results in a smoother and particulate-free finish.
In electropolishing, ions are removed from a metal surface though electrochemistry and electrolysis. Unlike mechanical polishing which moves or wipes metal, tiny bits of metal are actually removed. This means that imperfections in the form of uneven surfaces and abrasives are smoothened so we're left with bright, clean results.
Improves corrosion resistance
Free iron and other particles left in metal products during the manufacturing phase reduce resistance to corrosion. Quality and durability are compromised (even if only by a short period) to result in 'substandard' products. Electropolishing doesn't eliminate but improves corrosion resistance by removing these particulates.
Improves brightness and reflectivity
Consumers want products with sheen as they equate it with newness and quality. Mechanical polishing can achieve this but to a lesser degree. Electropolishing produces a uniform luster faster and better which lengthens the life of products and improves salability.
Easy to clean
Any consumer will admit that cleaning rough, rusted metal bits is tough and seemingly pointless. The smooth surface achieved by electropolishing attracts less contaminants which reduces cleaning time and simplifies the task. This is especially important when manufacturing metal products for use in food, beverage, medical and chemical processes where contamination must be eliminated.
Removes stress
Processes like heat treatments and decarburization can cause stress and disturb layers in metal. As electropolishing removes metal, it evens out layers without introducing new stresses that could affect structural integrity.
Suitable for complex geometries
Metal products shaped into complex designs are difficult to polish with mechanical tools. Curves, edges and unusual shapes can be missed to produce uneven finishing. Not so with electropolishing which ensures that even complex shapes are smoothed and polished.
Uniform and fast
Every industrial process benefits from uniformity and speed. Metal finishing is no different and electropolishing is superior to other techniques as the process is fast while maintaining uniformity. Labor cost is reduced, productivity is increased and savings are generated.
The process works on most metals though the presence of silicon, sulfur and lead produces less than perfect results. Metals free of seams and non-metals and having fine grain boundaries are ideal candidates. Stainless steel, bronze, brass, copper, titanium and aluminum are metals which are frequently electropolished.
Like all processes, the technique is not without disadvantages. However, these drawbacks have more to do with lack of process controls and insufficient process knowledge. Common problems resulting from inferior electropolishing include irregular patterns, pitted and pebbly surfaces and streaks and stains. What is indicative of high quality polishing is the absence of grain boundaries when viewed under high magnification.
Now that we've seen how electropolishing benefits consumers and makers alike, we come to understand just how important a process it is in the finishing phase of manufacturing. Traditional methods still hold sway if the technology is unavailable but for extremely well finished products, there's no substitute.
