Marine corrosion / sacrificial anodes...

[Externet]

Hi all.

The basics are simple, the currents produced by dissimilar metals in seawater, the erosion and deposition of material depending on the electronegativity...

 

I see it as a simple galvanic cell, a 'battery', but I have a void somewhere in all this.

If an iron barge floats on seawater, and no other metals are part of its hull, will still need (Zn, Al) sacrificial anodes attached ?

 

If an aluminium boat hull has a bronze propeller I can understand the migration of charges and erosion of metals; but what if the hull is only aluminium and no other metals, will it still deteriorate and need protection ?

 

Now, an aluminium hull has good electrical connection with its stainless steel shaft and bronze propeller, as they are all attached to each other... how does the corrosion/electric currrents work there ?

 

If a boat with aluminium hull is 20 metres away from an iron one; will there be electrical / ionic / metal migration / currents in the seawater and between the boats ?

 

Any clear light is welcome. I believe am mixing battery reactions, electrolysis and electroplating...

 

Miguel

[foodchain]

http://en.wikipedia.org/wiki/Hydrogen_embrittlement

http://www.echamicrobiology.co.uk/pages/tank_and_hull_corrosion/1,23/default.aspx

 

I don’t know if these will help but its all I could pull of the top of my head.

 

*Thinking about it the second one is scary thinking about evolution. What if the bacteria eat all our metal ,LoL.

[YT2095]

the thing to remember is that although it is a battery of sorts, it`s also one that`s been shorted out.

so for instance your 2 boats 20m apart will indeed have an electrical potential, but will react in no way at all unless they make electrical contact with each other.