What is chemical polishing?                  
Chemical polishing is a method by soaking a component and dissolving and removing the bulge of microscopic uneven surface, via chemical etching.  Compared with the surface prior to polishing, the unevenness is reduced and thus make the surface tend to be smoother.
Illustration of Electrolytic chemical polishing

                     Illustration of chemical polishing process 

Various surface treatment techniques

various treatment techniques

Advantages and disadvantages of various polishing techniques

Grinding(Milling) Rolling Electropolishing Chemical polishing

Techniques Problems Suitable applications
Remaining particles, wax, and fragments easy to remain on the components or splash around.
Particles, wax, and remainders trapped inside hollows on surface not easy to come off.
Environmental impact large.
Suitable when the high level of decorative or the sanittary
finishing is not required. 
Labor and equipment cost high.
Impossible to polish inside.
Shart point or edge of the component becoming round.
Components easy to deform.
Easy to leave abrasive traces.
Same as basic polishing and milling.
Suitable for rounded shape required.
Impossible to polish inside.
Typical efficiency.
Every single part needs to be hung and
connected to electrodes.
Attaching an electrode inside a pipe not
easy or not possible.
Needs to heat to 70℃ and adjust the solution. concentration. Needs tight site environmental
control and proper waste water disposal.
Suitable for relatively large and simple components
Very low efficiency 
Some components impossible to process
Some components impossible to be replaced by chemical polishing
Chemical Polishing
Any shape is ok, no need to hang individual parts, no need to add an electrode. Just need to load the components in a basket.
The parts touching and being submerged in the chemical solution becomes polished. 
Needs to heat to 96℃, Needs tight site environmental control and proper waste water disposal.
Inside of a long pipe, of various components, of curved parts can be polished.
Applicable for small and thin parts, shiny parts, parts with no machining traces, parts with no burrs, parts with utmost cleanliness, and parts which are impossible to electropolish. 
Efficiency very high.
Completely possible to replace electropolishing, but not the other way around