How to Electropolish Stainless Steel
Electropolishing is an industrial process to clean stainless steel surfaces. It is also serves the purpose of reducing micro roughness and a host of other highly desirable traits on stainless steel.
Electropolishing is based on the principle of electrolysis. A flow of current, a solution of sulphuric acid (for the most parts) and an orthophosphoric as an electrolyte is used in this process of electrolysis. Electropolishing stainless steel is not a very time consuming process. It takes a minimum of two minutes and a maximum of twenty minutes. The length of the procedure depends on the size and shape of the work piece.
Working Principle of Electropolishing
A passing electric current is applied to a workpiece that is immersed in an electrolyte of a particular composition. This is the basic working principle of Electropolishing. One could say that this is in sharp contrast to the function of Electroplating, where metal ions are deposited from the solution and then added to the work piece. The opposite takes place in Electropolishing where there workpiece under goes corrosion, and by doing so releases the metal ions into the solution.
The Setup for Electropolishing
The setup for an Electropolishing system is in large parts similar to that of Electroplating. The Electropolishing installation involves a power source that converts AC current into DC current at low voltages. The chemical bath is contained within a plastic or lead-lined tank.
A succession of stainless steel cathode plates is dipped into the bath, near the negative side of the power source. An individual stainless steel component or a number of stainless steel components is attached to a metal rack made that is usually formed from titanium, bronze or copper. The rack is then joined to the positive side of the power source.
This means that the stainless steel work piece is linked to the positive terminal while a apposite conductor is connected to a negative terminal. To form a complete electrical circuit, both the negative and positive terminals are sunken in the electrolyte. The passing current is a DC current.
An Electropolishing System in Motion
During Electropolishing, the stainless steel at the anode is dissolved into the solution. As a result, a soluble salt of the metal appears in the solution below. A controlled smoothing of the surface is produced as the reaction occurs on all components of stainless steel. A series of side reactions take place as well. These must be kept under control to ensure that the Electropolishing produces the best rest results.
A generic Electropolishing solution contains equal parts 96% mass fraction sulphuric acid and 85% orthophosphoric acid. The conditions that are conducive for an Electropolishing operation are:
1) Current density of 5/A dm2 to 25/A dm2
2) A temperature range of 40 C to 75 C
3) A duration of 2-20 minutes as mentioned before
4) Stainless steel cathode
Post Electropolishing Treatment
Once Electropolishing is complete, a nitric acid post treatment is required. The post treatment is carried out to liquefy the thin layer of chemical by products that accumulate following the electrochemical reactions. These by products comprise of sulphates and phosphates of heavy metals, and cannot be erased by simple water rinsing. The removal of these impurities is absolutely crucial to ensure that the effects of Electropolishing last longer.
Cougartron ProPlus for Electropolishing
If you are looking for seamless Electropolishing of stainless steel, then the Cougartron ProPlus is the system that you need. This system provides superior, swifter and safer Electropolishing in a super compact format. It does so with the use of intelligent electronics which provide unswerving power and zero interruptions. Electropolishing is made much easier with the use of Cougartron ProPlus.