Black Lead

jfkal

jfkal

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Checked up some details on that. Black lead is actually graphite and shows up in the table on corrosion as even higher than platinum! That means it makes an excellent battery with the prop and saltwater. Has anyone actually used it without getting the prop eaten away? And if it works without causing electrolytic corrosion WHY?
 
was going to put it on tomorrow I am talking ZEBO range black polish, is that black lead? dont want my thingy falling off.:-)


Dave
 
Re: Black Lead Total waste of time

I applied this 2 years ago - might just as well not have bothered.
Last year smeared it with Vaseline - good results - few small barncles after 11 months in.
This year used Lanolin - put on with a blow torch - expecting better results
 
Think Zebo is a no-no...

From what I can gather, all these graphite-based products are bad news from a corrosion point of view. I can't see much logic in expecting any sort of prop coating to remain intact for long, when you consider the action of high-speed rotation of the prop.
 
I actually asked all the propeller manufacturers at the trade show at Windsor in October last year what they recommended for propellers, if anything at all, and what they all said was that it was entirely personal preferance wheather to apply anything or not, BUT anything containing anything metallic MAY cause de-zincing, so thee you have it.................or not.........
 
I think it\'s \"or not\"

To get dezincification there needs to be some zinc in there in the first place, i.e. the propeller should be made of brass. I would find it surprising to find that any commercial propellers were made in brass, as the poor corrosion properties of this range of alloys do not lend themselves to prolonged immersion in seawater.

Propellers are normally made from a bronze (copper and tin) alloy, of which there is a wide range of possible compositions. None contain more than a few percent of zinc, mainly for deoxidation during the casting process. There is a very low likelihood that this would be preferentially removed and it would not do much harm if it was.

Graphite can be surprisingly active in combination with certain metals in seawater but I would not expect bronze to be badly affected by it. My experience of seawater systems is that graphite in spiral wound gaskets can cause rapid and severe loss of stainless steels.
 
Re: I think it\'s \"or not\"

I am only repeating what the propeller manufacturers told me, they should know if anyone dose.......are you a propeller manufacturer???
 
Re: I think it\'s "or not"

What would you recommend be used on a bronze propellor fitted to a occassionally used (e.g. 10 times a season) yacht which otherwise sits on a mooring in Portsmouth harbour? Options seem to be, polish propellor - no coating, vaseline, black lead, lanolin or hard antifouling.
 
I've used it (black lead) on props for years, without any problems, and good antifouling results, Mind you the stuff I use, I'm pretty sure is not graphite, I'll check and get back to you.
 
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