Cleaning zinc anode

[Miker]

I've removed my zinc shaft anode and wire brushed off about 60% of the white chalky coating, but can't get at the remainder deposited in the pitted surface. Can anyone recommend something that will do the trick? I've read that vinegar might work but have yet to try it. Also, does the white deposit adversely affect the conductivity of the anode, and, if not, should I bother?

My prop is an Autoprop. Its prop anode which I change every year lasts a summer season of around seven months, but no more.

 

[vyv_cox]

I believe the deposit is zinc hydroxide, which is not dissolved by very much. I file mine to remove most of it. This deposit is formed heavily in fresh water and has to be removed to re-activate the anode.

My Autoprop anode lasts a season without a shaft anode but it lasts two seasons when one is fitted. The shaft anode does two or three seasons.

 

[johnalison]

An anode will self-clean in a couple of weeks in the water, but protection will be reduced in that time. If you are re-immersing an anode after a period outside, usually a wire-brush will be enough to re-activate it, as long as some of the metal is exposed.

 

[rob2]

I'm not sure what would be the "best" way to clean them, people have different methods and opinions. I once cleaned one that was severely coated. I found that the outer layers of the deposit were fairly friable and could be removed by wire brush, but closer to the anode material it was very hard and I had most success using a chipping hammer - slow but effective. The final finish was very rough, so I smoothed the worst off with an angle grinder just to improve water flow, despite the loss of anode material.

Rob.

 

[Miker]

Thanks everyone. I think that a bit more work with a wire brush and file is needed.

 

[awol]

Ordinary wire brushing is not a particularly good idea as some sources believe it can lead to passivation of the anode e.g. from the Volvo site (any suggestion that they have a vested interest in selling anodes would be cynical)

"If an anode for example looks yellow or is covered in white crust it has been pacified and needs to be brushed or changed to provide protection. This can be done by brushing the anodes using sandpaper or an emery cloth. Note, never use a wire brush with steel bristles. You have to use an emery cloth without iron oxide otherwise the anode might be pacified."