Sciencemadness Discussion Board

Na2Cr2O7 destroying cell?

Fantasma4500 - 27-3-2013 at 16:35

just recently i got a small yield of KClO3 starting with NaCl at low amp.. i was pretty glad about this, i used a SS spoon, unknown alloy, tho.. but probably standard food grade..
i added in Na2Cr2O7, as said it runned at usually 3 amps - +
i didnt have any realy problems with corrosion..
i now put my cell back together again, and made a completely saturated solution, in which the other most likely wasnt due to the low amps, now i got as much as 19 amps, starting at 8 amps
it runs on 12 volts from a car battery charger
anode: MMO
cathode: steel spool

i then took another spoon as the other spoon i used before was ruined, put the cell back again and made it run..
i did test the spoon before (which was many times brighter than the other spoon)
i tested it with graphite anode in saturated NaCl
the spoon was used as cathode for roughly 10 mins and came out just as smooth as before..

there was no Na2Cr2O7 in at this time
as the last mistake with the other spoon i added even more Na2Cr2O7 just to be sure..
the corrosion on the cathode / ss is like a fluffy mush of rust.. relatively easy to filter off..
i keep my cell in a water bath to keep the temperature down, also when using the new spoon i didnt smell any chlorine or notice any bubbles in the scrubber..

could the Na2Cr2O7 be ruining my cathode, or is it the higher amps??

Fantasma4500 - 31-3-2013 at 08:01

think i have possibly found the explanation for the steel tearing up, insuficcient cathode areal for the hydrogen to form on, thereby it rips the steel apart, tho it sounds weird, could be the reason as it would form much more hydrogen at higher amps which is where it starts messing up

plante1999 - 31-3-2013 at 08:11

S.S is not a very good cathode, and 12 V is way too much! You should use 3.33 V, at max 6, not 12!

garage chemist - 31-3-2013 at 08:39

Stainless steel is unsuitable as a cathode since nickel ions will be formed through corrosion, and these mess up the chlorate producing reactions by catalysing the decomposition of hypochlorite into oxygen and chloride. Nickel ions can seriously lower your cell efficiency.
Use a strip of Titanium sheet as cathode and your corrosion problems will be solved.

plante1999 - 31-3-2013 at 08:42

He could use bare iron with more dichromate in the electrolyte too.

Fantasma4500 - 1-4-2013 at 12:45

Quote: Originally posted by plante1999  
He could use bare iron with more dichromate in the electrolyte too.


ive heard about iron, but ive heard SS should be the best as a cathode??
also with iron i believe i need not just a pinch of dichromate but as much as 10g / litre!
thats starting to sound abit toxic to me.. (:

also you got any idea how to lower the voltage? i have some problem with the cell getting really hot so i have it in a ~10-15L waterbath, which also at one point gets somewhat hot.. :P

[Edited on 1-4-2013 by Antiswat]

Fantasma4500 - 1-4-2013 at 12:48

Quote: Originally posted by garage chemist  
Stainless steel is unsuitable as a cathode since nickel ions will be formed through corrosion, and these mess up the chlorate producing reactions by catalysing the decomposition of hypochlorite into oxygen and chloride. Nickel ions can seriously lower your cell efficiency.
Use a strip of Titanium sheet as cathode and your corrosion problems will be solved.


as youre from europe yourself.. have you seen any selling titanium? i would like some titanium actually..
im currently testing out a chain for use as cathode, it seems quite reliable as i havent even gotten it to react with HCl as the anode, electrolysis of HCl with steel as anode!!

but if you see some selling some pieces of titanium relatively cheap in pieces thats well about 5 x 12 cm or alike that please tell me (:

garage chemist - 1-4-2013 at 13:48

Just have a look at Ebay. There are many sellers of titanium sheet that ship worldwide.
This is the type of sheet that I'm using in my perchlorate cell, 1mm thick, Grade 2:
http://www.ebay.de/itm/Titanblech-Titan-Blech-1mm-Grade2-300...
Ending very soon.

Or this one, Grade 1 (chemically pure Ti), but only 0,6mm thick, you can choose the cimensions:
http://www.ebay.de/itm/TITAN-Blech-0-6mm-Reintitan-Grade-1-T...

Fantasma4500 - 1-4-2013 at 22:18

Quote: Originally posted by garage chemist  
Just have a look at Ebay. There are many sellers of titanium sheet that ship worldwide.
This is the type of sheet that I'm using in my perchlorate cell, 1mm thick, Grade 2:
http://www.ebay.de/itm/Titanblech-Titan-Blech-1mm-Grade2-300...
Ending very soon.

Or this one, Grade 1 (chemically pure Ti), but only 0,6mm thick, you can choose the cimensions:
http://www.ebay.de/itm/TITAN-Blech-0-6mm-Reintitan-Grade-1-T...


thanks alot! i have searched abit around for titanium on ebay, also ebay.com!
what i found was only MMO, which i already have..
its about knowing the words for these things (:
i will look further into it later today..