Prop corrosion (see pic)

[TwinRudders]

Afternoon,

Took my Beneteau First 285 out of the water yesterday - prop looks awful.


It's a Bruntons 2 blade folder - new in last year. Clearly something fairly wrong. Wastage on the anode isn't as much as I would expect so obviously the prop is taking the brunt of the electolysis...But why?


OK I didn't have a shaft anode on but even so it looks pretty severe to me.
I have shore power - but not used very often - and have a galvanic isolator fitted. Earth lead is def fitted to the anode.

Any suggestions...tests to do?

Thanks,

Jonny

 

[Ruffles]

Twinrudders,

Are you sure that's not just calcification? Clean it up first by scraping it, wire brushing or, as I did when I took mine off this year, hydrochloric acid! Then polish it up with wet-n-dry.

If it is coroding it will show pink spots rather than brassy/bronze.

 

[Aja]

Difficult to tell from the angle - but is your Stripper correctly aligned with the fitting on your P-bracket?

As for the prop - is the metal pitted? It could be calcification right enough.

Donald

 

[Miker]

My Bruntons two blade looked worse until I cleaned it with wet and dry to get the crud off. Not quite gleaming yet but it was all crud, no cathodic action. Perhaps I'm neurotic but I've also got a shaft anode and a shaft brush wired to a hull anode.

 

[Ruffles]

As I said, I took advantage of having the prop off, and cleaned mine with concentrated hydrochloric acid. After much fizzing it was clean. No scrubbing or scraping. Def. something to do in fresh air though....

Buffed it up on a bench polisher. Job done at home in 5 minutes.

Anyone got any advice on how to straighten out the odd ding on a blade tip?

 

[nigelhudson]

I suggest that you check the continuity between the anode and the shaft - it should be less than 10ohms resistance. Also rotate the shaft whilst you are checking to see if it changes. It may be that you do not have a proper connection between the anode and the shaft.
If you do not have a proper connection you have two choices in addition to the shaft anode - fit an earth brush to the shaft or earth the shaft when not in use. The former will cost approx £50 unless you can fabricate one yourself. I've chosen the latter - I connect the shaft to the anode stud with an old jump lead whilst in the marina. Just remember to remove the jump lead before starting the engine!

 

[DickB]

I think I would be very wary of acid. From my chemistry days at school I recall H2SO4 just loving bronze... I think it takes out the copper component first... Could be a very expensive dipping!!!!

 

[Jodel]

[ QUOTE ]
I think I would be very wary of acid. From my chemistry days at school I recall H2SO4 just loving bronze... I think it takes out the copper component first... Could be a very expensive dipping!!!!

[/ QUOTE ]

But H2SO4 (sulphuric acid) is not the same as hydrochloric acid (HCL)