What exactly was electro-polishing?

[es9]

I’ve seen advertisements listing the incredible benefits of Parker’s electro-polishing nibs, but what exactly did the process involve? 

[dipper]

Electropolishing is the reverse of electroplating. Metal is removed instead of being deposited.

 

The workpiece to be polished is connected to the positive terminal - removing metal. That is the reverse of being connected to the negative terminal to plate the workpiece - depositing metal.

 

The electrolytic polishing process dissolves the metal surface. At low currents it removes metal slowly and can be used to etch logos etc. or to "machine" complex forms.

At high currents the process preferentially removes all the spiky bits of the metal, down to microscopic sizes, giving a shiny gloss surface. It also rounds off corners, burrs and sharp edges - so it is conceivable that it could be a beneficial step in nib manufacture.

 

I have experimented with elecro-etching and electro-polishing of stainless steel.

I etched a "UK" mark onto a stainless steel ruling pen sent from the UK, to satisfy US import regulations.

 

Used a 12volt car battery charger, a bowl of water containing salt solution (or was it washing soda?), cables, croc-clips, and copper pipe scraps as electrodes.

Connect the metal to be etched or polished to the positive terminal and bring the other electrode into near-contact through a short distance of salt solution. Either submerged, or through a wet pad of paper towel.

I masked the logo to be etched with nail varnish. It worked! And some parts of the relief-etched area came out shiny. Unintended electropolishing!

 

 

There are many variants in equipment, electrolyte, and working methods.

 

 

 

[es9]

Interesting. So why don’t folks do it anymore? 

[txomsy]

Thanks for the explanation. I didn't know and fully appreciate it.

 

 

 

[TheRedBeard]

On 4/25/2023 at 2:31 AM, dipper said:

Electropolishing is the reverse of electroplating. Metal is removed instead of being deposited.

 

The workpiece to be polished is connected to the positive terminal - removing metal. That is the reverse of being connected to the negative terminal to plate the workpiece - depositing metal.

 

The electrolytic polishing process dissolves the metal surface. At low currents it removes metal slowly and can be used to etch logos etc. or to "machine" complex forms.

At high currents the process preferentially removes all the spiky bits of the metal, down to microscopic sizes, giving a shiny gloss surface. It also rounds off corners, burrs and sharp edges - so it is conceivable that it could be a beneficial step in nib manufacture.

 

I have experimented with elecro-etching and electro-polishing of stainless steel.

I etched a "UK" mark onto a stainless steel ruling pen sent from the UK, to satisfy US import regulations.

 

Used a 12volt car battery charger, a bowl of water containing salt solution (or was it washing soda?), cables, croc-clips, and copper pipe scraps as electrodes.

Connect the metal to be etched or polished to the positive terminal and bring the other electrode into near-contact through a short distance of salt solution. Either submerged, or through a wet pad of paper towel.

I masked the logo to be etched with nail varnish. It worked! And some parts of the relief-etched area came out shiny. Unintended electropolishing!

 

 

There are many variants in equipment, electrolyte, and working methods.

 

 

 

 

Thank you very much for such a detailed explanation.

Very useful to know.