What is the purpose of an Annode when fitted to a boat and why is it fitted?

Question

What is the purpose of an Annode when fitted to a boat and why is it fitted?

Answer 1

Formersa is bang on the money and therefore quite noble. hehe

Answer 2

its for electrical discharge on a boat simlar to an earthing rod for a house. for metal boats.

hope this helps

Answer 3

formesa it tottaly correct

Answer 4

When two different metals are placed together in an electrolyte, like salt water, an electron flow will occur taking metal from the weaker to the stronger (or nobler).  Zinc is the weakest and will deteriorate leaving the nobler metal intact.  Anodes are also know as 'sacrificial zincs'.

Answer 5

All metals fall somewhere in the 'galvanic series' from bold or 'noble' ones like gold and the bronzes at the top, to the dull or 'base' ones like lead and zinc at the bottom of the series. Regardless of whether they are mixtures of more than one metal (alloys), or pure.  

Dissimilar metals in a saline environment will form a galvanic 'cell' - act in exactly the same way as a lead/acid car battery: The bold metals will act as cathodes, the base ones as anodes. A current will flow between them and the most base metal present will corrode away.

'Sacrificial' anodes are therefore fitted to the vessel to provide 'cathodic protection'. They are made deliberately from very base metal so that all the other metals present will be cathodes and will be protected as they, the most base one, corrode instead. They are also fitted in such a way as to be easily replaced when they have corroded away.

In good boatbuilding it is essential to ensure that where, inevitably, dissimilar metals are used - particularly in close contact such as fittings and their fixings - they should be as close together in the galvanic series as possible.

If sacrificial anodes are corroding away a lot - they are well fitted and are 'working'.

If they remain in good condition and are not corroding away as each season progresses - then they are poorly fitted (probably in a bad location) and are not 'working' so should be moved, or supplemented with others.

It is most important that sacrificial anodes are not painted, or coated in any way, as this will form an insulating layer and stop them from doing their job.

Answer 6

IT HELPS PREVENT CORROSION