@URI, I don’t know which model of T12 power supply you’ve looked at but on mine solder mask is not being used as the means of isolation. The psi sits in 2 channels on the side walls close to the bottom, there is a gap of around 6mm between the trace side of psi and metal case and in this gap there a piece plastic insulation. Granted there are 2 tracks that actual go into channels, and run the length of the pub. I was concerned about this myself as the case was not earthed so I investigated further and found that those 2 tracks in the channels were in carrying the earth connection from the rear terminals to the front to earth the socket and iron tip. Therefore I concluded that the only modification needed was to bond all the metal case parts to each other and the main incoming earth connection.
I've ordered the KSGER T12 controller.
The KSGER 24V switch mode power supply you can also order it with has a serious design flaw, check this:
https://www.youtube.com/watch?v=QESGY5LzPPw&feature=youtu.be&t=154I have had mine now for 2 years and have never had any trouble with them at all and I have worked on many sensitive parts with the iron connected to the house ground and have not destroyed anything yet.
EDIT.
I just read your reply above, there is no point in providing a earthed lead to the tip that you can then connect to your ESD mat or to house ground since that require a return path to the leakage voltage source that your trying to eliminate. There will not be a path for this leakage to dissipate to ![Evil >:D](https://www.eevblog.com/forum/Smileys/default/xevil.gif.pagespeed.ic.tdrs7Uj5gu.png)
With your tip grounded to earth you are just lucky to not having destroyed any ESD-sensitive parts. An earthed tip doesn't limit currents of ESD discharge.
I think I was not clear enough describing the connector to the tip:
I will add a 4mm plug socket that is connected to the tip. The tip is freely floating.
With this I can then connect the tip to whatever is appropriate for the solder job to be done.
- tip left free: freely floating, not ESD compliant
- tip connected to ESD-hub (1MOhm in series through ESD-hub-connection), ESD compliant
- ...