What Is Electropolishing and 
                 What Does It Do?

    Electropolishing is an electrochemical process performed primarily 
on stainless steel. It is similar to electroplating, but is anodic  in nature 
meaning is exactly the reverse. Metal is selectively removed under 
controlled conditions of temperature, amperes and time.
     1st material is removed, the surface becomes smoother because 
the microscopic high points of the metal surface are removed at a 
faster rate than the low points 1 micro and macro projections, and 
depressions). When the current is applied, a polarized film forms on 
the surface of the metal which allows the metal ions to diffuse through 
the film.
    The high current density areas (high points and buns I are dissolved 
away at a greater rote resulting in smoothing, leveling and debarring. 
Brightening of the surface, known as anodic luster, takes place 
simultaneously, which is where the term electropolishing derives from.

   The surface finish obtained by electropolishing is primarily a function 
of the surface quality and finish before processing. Brighter finishes are 
obtained be increasing time, temperature, and/or current density, which
also increases metal removal from high current density areas. This must
 be considered when dimensions are of critical tolerance.
     During the process hydrogen is liberated from the cathode, and 
oxygen from the anode. This causes a partial passivation of the surface
and improved corrosion resistance by leaving a transparent chromium
oxide film on the surface but, unlike plating, the problem of hydrogen
embrittlement is nonexistent. A complete passivation, if needed, must
be performed as an added processing step after electropolishing.
    Surface brightness (anodic luster), accomplished through 
electropolishing, is different from that produced abrasively or mechanically
It is scratch-free, deformation-free and directionless, and the true metal
color is revealed. Contrary to popular belief surface brightness is not 
always a true measure of surface smoothness.
    The surface finish, in micro-inches, is usually reduced from 33 to 66 
percent. However, as the valises become lower prior to the process, 
the improvement percentage decreases proportionally. The greatest 
contributing factors toward poor results are large grain size,
non-uniform structure, noncompatible inclusions, directional roll marks,
salt or scale contaminations, and wide variations in beginning surface
conditions. Fine grained deposits are most important for tree reflective
finishes.