Black lead on props

[Guest]

P.B.O. printed an article sometime ago about how good black lead was on props . I would like someone to confirm that it does work O.K. with a standard manganese bronze prop on a stainless steel shaft. The article and photograph claimed the writer had used this treatment for three seasons but did not mention the metals involved . I would appreciate anyone's views that has tried this treatment. Ray F

 

[Guest]

Black lead is graphite !!

Modern black lead is Graphite which is very high up the Galvanic table. I would suggest it is not a good thing to put on a bronze prop due to corrosion possibilities.

 

[Guest]

Re: Black lead is graphite !!

This subject was discussed at great length in a US BB some time ago and the conclusion was as stated by David, that irrespective of how effective it was, the electrolysis danger was not worth the risk.

 

[Guest]

Re: Black lead is graphite !!

Many thanks to both of you .I did suspect that it was a dodgy thing to do but the article in the Boat Owner was quite convincing. I have used it and lost a prop ,which I thought was badly connected anodes but tests show they are in circuit. Thanks again Ray

 

[Guest]

Re: Black lead is graphite !!

Used Zebo on the manganese bronze propeller on a stainless steel shaft last season on my Eclipse 33. Propeller perfect at the end of the season, no more than usual loss from the anode, no sign of deterioration anywhere. Shaft is earthed with MG Duff brushes and all main fittings properlly earthed together. Zebo certainly seem to keep the fouling away and stays on unlike any paint. Doing it again this year.

 

[Guest]

Re: Black lead is graphite !!

Tom, Many thanks for your contribution ,I am now completely confused . I do agree it keeps the prop clean but I obviuosly have another problem. Where do you keep your boat ? Ray

 

[Guest]

Re: Black lead is graphite !!

Tighnabruaich in the Kyles of Bute. A high fouling area with lots of growth of all descriptions particularly late in the season. Micron Optima keeps the bottom clean.
Interestingly in the magazine PCE, Protective Coatings Europe , April edition there is very considerable learned discussion about the effect of dissimilar metals in juxtaposition in corrosive environments. The general conclusion is that the more noble metal does not in any way accelerate the corrosion of the less noble if they are electrically bonded in an electrolite such as sea water.