metalresearcher - 29-1-2012 at 13:44
During an electrolyzing session of a saturated solution of Diet salt (2 parts KCl and 1 part NaCl) to make KClO3 I saw after several hours running
that the stainless steel cathode has black stains and when I rinse it with water and rub over the cathode, brownish yellow rust appears. Small
quantities remain in the solution as the original piss-yellow (due to a knifetip of K2Cr2O7) solution gets a bit greenish.
The anode (MMO) has no problems.
Is stainless steel getting attacked by the bleach ? Bleach is also formed by this electrolysis.
[Edited on 2012-1-29 by metalresearcher]
plante1999 - 29-1-2012 at 15:52
I have observed the same effect with my first mmo anode cell which had a stainless cathode and a mmo anode, I runned the cell without aditives. Black
stain was formed on the cathode and turned white upon standing in air.
[Edited on 30-1-2012 by plante1999]
Mailinmypocket - 29-1-2012 at 17:29
Something similar happened to me...however it isnt corrosion per se... I have been running a KClO3 cell using an MMO anode AND cathode, the cell
works great and I have used the same electrodes for 5-6 runs. I have noticed that the cathode develops a white coating which cannot be washed off,
before starting a new cell with the same cathode I am always worried that it has passivated or something and that this white coating has and/or will
affect its performance but it doesnt appear to.... :s
In the attached photo it seems like the white coating is a crust that can be scraped off... but it isn't! as soon as I run the cathode under tap water
the MMO turns back to black, when it dries the white re-appears yet cannot be scraped off! I am not sure what is going on... doesnt affect KClO3
production though...or, it doesnt seem to at least...
I dont know if this is relevant but just thought I would share. I use DI water for the KCl electrolyte so I know it isnt insoluble residues from tap
water.
[Edited on 30-1-2012 by Mailinmypocket]
cyanureeves - 30-1-2012 at 17:18
i get the same white build up on my titanium cathode. i have been running the cell for weeks and weeks through cold and warm days. we've had a mild
winter this year and i have decided to run the cell until the cheap 5 volt 3 amp switch mode i got on ebay gives out. it just keeps on working and i
know i already have about two pounds at the bottom because i've scooped some out and burned it. i used to scrape off the cathode but stopped doing so
because it doesnt interfere with conductivity, i think its potassium carbonate.@metalresearcher. have you tried looking for broken oakley titanium
sunglasses or knives at resale shops or camping pots so you can use titanium for cathode?
[Edited on 31-1-2012 by cyanureeves]