Corrosive current and conventional current 2

[power2020]

Dear Folks,
I am new to this forum. Could you pl. explain me the difference between corrosive current and conventional current (impressed current to avoid corrosion)?
Advanced thanks...

 

[mshimko]

Here's my go at it:

There are nearly always DC current passing from metal-to-metal when the metals are immersed in an electrolyte. Even for a simple, uniform material (a block of C-Steel, for example), there are DC currents between microscopic areas of the block.

Some will call these "corrosion currents", some will call them "stray currents", but to me, they are simply naturally occuring "currents".

Most corrosion in nature can be explained using an electrochemical cell model (also called a galvanic cell), comprised of an anode, cathode, "external electrical connection", and a common electrolyte. From this perspective, most forms of corrosion in nature are actually "galvanic in nature".

We categorize forms of corrosion by what essentially CAUSES the galvanic cell. That is, a crevice, a deposit, a change in chemicstry along grain boundaries, etc.

Sacrificial anode cathodic protection is identical to galvanic corrosion, with a minor exception: Galvanic Corrosion is the term used when you don't want "the" material to corrode. Sacrificial anode cathodic protection is when you WANT "the anode" material to corrode, which at the same time protects the "other" material.

Electrical current is involved in galvanic corrosion, and sacrificial anode cathodic protection, and are "the same currents".

In Impressed Current Cathodic Proptection (ICCP), we use an "external power source" and non-corroding anode to provide the current that protects the structure.

Hope this helps//mjs

 

[0707]

The conventional current is the one that flows from the anode to the cathode through a metallic contact

The corrosive current is the one that flows from the cathode to the anode through an electrolyte

luis marques

 

[0707]

In my previous posting I am speaking of current electrons flow which shouldn’t be misunderstood with electrical current flow. The electric current is opposite the electron flow.


luismarques