| Any metal when immersed in an electrically
conductive fluid, has a specific electrical potential that is measurable
as a voltage. As you can also see in the table below, it is true that
each metal has a different electrical potential when immersed in the
same electrolyte ( an electrically conductive fluid such as sea water).
As a result, if two dissimilar metals are placed in the same electrolyte,
their different electrical potentials will produce a voltage that
can be measured on the two pieces of metal. According to the potential
difference of these two metals, the current flows from higher voltage
metal to the lower one. This action raises the voltage of the lower-voltage
metal above its natural potential. To establish the equilibrium, the
lower-voltage metal discharges a current in to the electrolyte. The
current passes through the electrolyte back to the higher-voltage
metal and completes the electrical circuit between the two pieces.
The current flowing through the electrolyte is generated by an electrochemical
reaction that steadily consumes the lower-voltage metal a process
known as galvanic corrosion. |
|
Table of Galvanic Series
in Sea Water
|
Range of Corrosion
Potential
(in Volts)
|
 |
Magnesium
and Magnesium Alloys |
-1,60 to -1,63
|
| Zinc |
-0,98 to -1,03
|
| Aluminum
Alloys |
-0,76 to -1,00
|
| Mild
Steel |
-0,60 to -0,71
|
| Wrought
Iron |
-0,60 to -0,71
|
| Cast
Iron |
-0,60 to -0,71
|
| Type
410 (13% Chromium) Stainless Steel - Active
in Water |
0,46 to -0,58
|
| Type
304 (18-8) Stainless Steel - Active in Water |
0,46 to -0,58
|
| Type
316 (18-8, 3% Mo) Stainless Steel - Active
in Water |
-0,43 to -0,54
|
| Inconel
(78% Ni; 13.5% Cr; 6% Fe) - Active in Water |
-0,35 to -0,46
|
| Aluminum
Bronze (92%Cu; 8% Al) |
-0,31 to -0,42
|
| Naval
Brass (60%Cu; 39%Zinc) |
-0,30 to -0,40
|
| Yellow
Brass (65%Cu; 35%Zn) |
-0,30 to -0,40
|
| Red Brass
(85%Cu; 15%Zn) |
-0,30 to -0,40
|
| Tin |
-0,31 to -0,33
|
 |
Copper |
-0,30 to -0,57
|
| Lead-Tin
Solder (50%-50%) |
-0,28 to -0,37
|
| Admiralty
Brass (71%Cu; 28%Zn; 1%Sn) |
-0,28 to -0,36
|
| Aluminum
Brass (76%Cu; 22%Zn; 2%Al) |
-0,28 to -0,36
|
| Manganese
Bronze (58.5%Cu; 39%Zn; 1%Sn; 1%Fe; 0.3%Mn) |
-0,27 to -0,34
|
| Silicon
Bronze (96%Cu; 0.80%Fe; 1.50%Zn; 2%Si; 0.75%Mn; 1.60%Sn) |
-0,26 to -0,29
|
| Type
410 (13% Chromium) Stainless Steel - Passive
in Water |
-0,26 to -0,35
|
| Lead |
-0,19 to -0,25
|
| Inconel
(78% Ni; 13.5% Cr; 6% Fe) - Passive in Water |
-0,14 to -0,17
|
| Nickel
200 |
-0,10 to -0,20
|
| Type
304 (18-8) Stainless Steel - Passive in Water |
-0,05 to -0,10
|
| Monel
400 (70%Ni; 30%Cu) |
-0,04 to -0,14
|
| Type
316 (18-8, 3% Mo) Stainless Steel - Passive
in Water |
0,00 to -0,10
|
| Titanium |
-0,05 to +0,06
|
| Platinium |
+0,19 to +0,25
|
| Graphite |
+0,20 to +0,30
|
There is a greater likelihood for galvanic
corrosion between the two commected metals when the difference
of the electrical potential is greater between them.
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