Anode Question

[pondfish]

I was down a friends boat club and he had his new to him boat out doing hull painting and polishing I noticed he had put new anodes on but with a blue sponge type disk behind them,
We got into talking about anodes and I said i'm almost 100% sure the anodes should be in contact with the metal its protecting to work,
But he said they were on the old anodes when he bought the boat so he reused them,

What are your thoughts guys.

 

[maby]

I was down a friends boat club and he had his new to him boat out doing hull painting and polishing I noticed he had put new anodes on but with a blue sponge type disk behind them,
We got into talking about anodes and I said i'm almost 100% sure the anodes should be in contact with the metal its protecting to work,
But he said they were on the old anodes when he bought the boat so he reused them,

What are your thoughts guys.

Generally speaking, the electrical connection is via the bolt that is holding the anode on, not direct contact between the anode and the hull. Most boats are wooden or plastic hulls, so there is no point in ensuring direct connection between the anode and the hull. It is there to protect things like the steering gear, propshaft, possibly skin fittings or keel - all these items should be bonded to the anode via internal earth wires. If the boat is steel hulled, then the situation might be different.

 

[Sailorsam101]

If the boat is GRP then the foam disc thing is put there to protect the hull. The anode will be connected with the metal parts through the hull via the bolt that holds it on and various earth wires on the inside.

If there isn't any wires on the inside then they are not protecting anything.

 

[VicS]

I was down a friends boat club and he had his new to him boat out doing hull painting and polishing I noticed he had put new anodes on but with a blue sponge type disk behind them,
We got into talking about anodes and I said i'm almost 100% sure the anodes should be in contact with the metal its protecting to work,
But he said they were on the old anodes when he bought the boat so he reused them,

What are your thoughts guys.

As said the electrical connection to the anode is via the fixing studs

From various sources:

Anode backing pads are used with anodes on steel hulls to prevent the anode corroding from the mounted surface, which could cause the anode to fall off of the insert support. Backing pads are also used to avoid saponification of paint (the softening or liquefying of paint) caused by alkalinity that is produced around the anode.

On GRP or wooden hull an anode backing sheet must be used to control the wastage of the anode and protect the hull.

The anode backing sheet should be replaced each time the anode is replaced.

Always ensure that the anodes are fitted with fan disc washers under the securing nuts which will help to enssure the contact between anode and cathodic protection system. The fan disc washers and nuts should be replaced each time the anode is replaced.

Protect the anode fixing studs on assembly with paint or grease inside and outside the vessel.