Positioning of shaft anode

[coopec]

Regarding zinc vs aluminium in brackish water. Fresh to salt water is a spectrum therefore, I assume, going from an estuary up a river the saline level will not only progressively diminish but also vary according to ebb and flow of tide At what point do aluminium anodes become advisable? For myself, I don't have a choice as Darglow don't make aluminium anodes for the Featherstream prop and I don't want to mix zinc and aluminium.

This article may help?

Sacrificial Anodes FAQs

 

[vyv_cox]

Aluminium anodes are now advised to be a direct replacement for zinc with several advantages. The alloy used is sophisticated and can in theory protect aluminium saildrives, although I do not know if any are available. I did an article on this in YM a year or so ago.

 

[erich27]

Hello Vyv

We keep our Sigma 35 ( with folding two blade bronze prop on a S/steel shaft ) on a swinging mooring in Holyhead harbour and wondered what your recommendation would be for a " good paint system " to protect the prop & shaft from excessive fouling ?

thanks
Erich

 

[vyv_cox]

Hello Vyv

We keep our Sigma 35 ( with folding two blade bronze prop on a S/steel shaft ) on a swinging mooring in Holyhead harbour and wondered what your recommendation would be for a " good paint system " to protect the prop & shaft from excessive fouling ?

thanks
Erich

First problem is keeping whatever you select for antifouling paint on the prop, which means a good primer. Because the components are non-ferrous an etch primer will work well. I have posted many times that I find Hammerite Special Metals primer to be excellent, offering good adhesion to aluminium, zinc, copper alloys, and reasonable on stainless steel.

So far as the A/F paint is concerned it may depend on location. I find Velox to give very good performance in the Aegean and most people have success with it in UK waters. Some find Trilux to work well but I have no experience with it. You will get better results by abrading the primer before applying top coat.

Look out for a radical approach to prop antifouling in an upcoming PBO. Next couple of months I think.