-- The Home Page of the Finishing Industry
23+ years of serious education, promoting Aloha,
& the most fun you can have in metal finishing smiley
    no popups, no spam
on this site
current topics
topic 10502

Electro-chemistry of Stainless Steel


We build small saline filled chambers for biological purposes. It is required to supply a voltage to a stainless steel electrode which is placed in direct contact with the saline. The saline consists of 150 millimoles NaCl and 16 millimoles of Na2HPO4 (Sodium dibasic Phosphate) which acts as a buffer. If a stainless steel electrode and a copper electrode are placed in this solution and a voltage of about 3.5 volts is applied, the cathode (copper) discharges gas, which we assume to be hydrogen. The anode begins to form a light green soluble substance which fits the description of ferrous chloride. However if we instead use 16 millimoles of NaH2PO4 (monobasic) we see a colorless gas (oxygen ?)at the anode and no green substance at all. Can someone help us with the electro-chemistry of this phenomenon?

George C. Malachowski
- Fort Collins, Colorado, USA.


At the anode you are generating Oxygen and Chlorine and Hydrogen at the cathode. The metals in the Stainless Steel are forming Chloride salts. Nickel Chloride, Ferrous Chloride and Chromic Chloride. If the pH is above 8.0, the Nickel will probably precipitate. In time, you may find deposited Iron on the cathode with traces of Chrome. The deposit will be smutty brown with possibly a slight green tint. If you continue electrolysis, the SS will dissolve completely. The Di Sodium Phosphate used alone should be OK. If you require the Sodium Chloride for some reason, I recommend you use either a Platinum metal anode, or a Platinum clad or Platinum plated Titanium material. Carbon can also be used but will eventually fall apart. Iridium Oxide is the best of all but may be cost prohibitive.

Rick Armstrong
- Anaheim, CA, U.S.A.

This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to Search the Site

ADD a Comment to THIS thread START a NEW threadView CURRENT TOPICS

Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices

©1995-2018, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.