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Corrosive current and conventional current 2
- Thread starter power2020
- Start date
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
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
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