VP "G" series prop corrosion

[GrahamHR]

I know corrosion of these Nibral props, fitted to DPH drives was brought up in 2009 or so; I didn't have any at that time.

Now I have some , after cleaning them up there are some pink areas on the hub, which are surface only as they can be polished out so it's early stages yet. I gather it's due to aluminium depletion ( Nibral is a Nickel;/ Aluminium. Copper alloy), akin to zinc depletion in a brass.

On the inside of both hubs there seems to be ample room to fit a reasonably sized circular anodes ( there is no exhaust flow through them). The props are not protected by the outdrive anodes as they are electrically insulated from them. Any negative effect of doing this ? Yes, I know, in an ideal world VP would have fitted hem if there was a benefit, but probably chose not to as the props would last just oustide the warranty period without them !

 

[volvopaul]

I know corrosion of these Nibral props, fitted to DPH drives was brought up in 2009 or so; I didn't have any at that time.

Now I have some , after cleaning them up there are some pink areas on the hub, which are surface only as they can be polished out so it's early stages yet. I gather it's due to aluminium depletion ( Nibral is a Nickel;/ Aluminium. Copper alloy), akin to zinc depletion in a brass.

On the inside of both hubs there seems to be ample room to fit a reasonably sized circular anodes ( there is no exhaust flow through them). The props are not protected by the outdrive anodes as they are electrically insulated from them. Any negative effect of doing this ? Yes, I know, in an ideal world VP would have fitted hem if there was a benefit, but probably chose not to as the props would last just oustide the warranty period without them !

There is no way an anode can be fitted to a rotating propellor as the vibration would be horrendous to the prop shafts and bearings.
Anodes fitted to shaft drive boats always seem to end up resting loose on the prop after a few weeks of being fitted if they erode quite quickly , the prop anodes on the French boats barely last with a result that the cap head screw falls off after erosion.

 

[GrahamHR]

Nice to get a reply ! Fitting a symmetrical anode internal to the hub surely, wouldn't cause any vibration? No more than fitting an anode to a prop shaft on a shaft drive would ? Mechanical erosion shouldn't be an issue, as they would be shielded ( mechanically, but not electrically)?

 

[volvopaul]

Are they stainless? Check for continuity between the hub centre and the blades .

 

[GrahamHR]

Are they stainless? Check for continuity between the hub centre and the blades .

No, they are Nibral. There is no continuity between the hub centre and the hub outer/ blades; there is a plastic bush between them ( like on the F series stainless props). They are not protected by the outdrive anodes. I'm not even sure the active corrosion protection system protects them; it might do though, as the control unit was indicating maximum current draw/ working at it's maximum level, something it never did with the F series props on my previous boat.