Farrah made a post that i believe should have its own thread.
"Under normal conditions the chromium oxide coating on ss is relatively impervious and so protects the underlying metal, but when we are forcing a heavy current through it in an oxygen rich environment such as our electrolysers, then any weaknesses in the surface coating will be exposed and any underlying reactive metal such as iron will of course react.
It is more usual that the anode is attacked this way due to the oxygen being formed, whereas the cathode is often unaffected.
What conditioning does is, by running a steady low current through the cell, weaknesses in this coating are exposed and iron at or near the surface reacts to form rust, which will precipitate into the solution and eventually form a sludge. As there is a lot more chromium in ss that iron, once the iron (or other reactive metal) has reacted and fallen away as an oxide, then more chromuim is exposed and this instantly forms it's protective oxide layer and all is well again. By steadily upping the current through the cell eventually all the iron and any other reactive metals near the surface will have been leached away.
Furthermore, while you are getting the oxygen reacting with such as iron on the electrodes, you will be seeing less oxygen evolved from your cell as gas - it will be busy forming the iron oxide.
Also consider this. Oxide layers are what protect copper and aluminium amongst other metals, and though they are generally insulators, they form such a thin coating that they do not do much to impede current flow. So like our chromium oxide they are relatively porous to tiny electrons. But try forcing too much current through these pores and this is when we start to get trouble as the pores can become holes and, in the case of our ss, expose underlying metals such as iron. So it pays to condition your cells this way initially to avoid the brown sludge and crud you will otherwise get.
This is probably also the main argument for limiting the current density on any electrode - to prevent electrode corrosion.
For a long time people thought it was down to the water being used and inpurities in the water, but in my experience the crud comes primarily from the ss.
Dave Lawton went on to condition his cells further, not to protect them, but to form a mineral layer that upped electrolyser efficiency. He went on to determine efficiencies of 3-4x over-Faraday.
The mineral layer (formed from minerals in 'hard' tap water) forms a coating on the cathode, which I now know allows for plasma discharges within the pores of this mineral coating. Plasma discharges are known to produce more gas from water than Faraday Electrolysis from any given power, but Lawton was achieving this as a by-product of Faraday Electrolysis by pulsing dc.
I've attached a photo of one of my test cells that clearly shows a heavy white mineral coating on the centre ss nut and threaded bar (my cathode). I enhanced Lawtons mineral coating by doping my water with calcium carbonate."
Attached Images
File Type: jpg Picture 384.jpg (102.3 KB, 0 views)