Strange anode usage

[VicS]

What about the copper coat or has there been a copper coating/sheathing near by? The only reason I mention this is that I found copper pipes black (in salty conditions) with a furry black deposit, so after a bit of google work I found there is a reaction between copper and zinc that produces a blackness on the zinc: http://chemed.chem.purdue.edu/demos/demosheets/9.11.html I cant comment if this link demonstrates a feasible mechanism, I have very little understanding of chemistry, perhaps this will help direct the investigation.

It's a well known bit of elementary chemistry (remember silvering pennies by dipping them in silver nitrate solution?) It's a possible explanation but I'd find it difficult to explain high enough concentrations of copper in the water to produce the effect. The experiment used M/10, equal to 25g copper sulphate crystals per litre. However its one of the reasons I suggested that it is necessary to identify the black material

 

[Tidewaiter2]

It's a well known bit of elementary chemistry (remember silvering pennies by dipping them in silver nitrate solution?) It's a possible explanation but I'd find it difficult to explain high enough concentrations of copper in the water to produce the effect. The experiment used M/10, equal to 25g copper sulphate crystals per litre. However its one of the reasons I suggested that it is necessary to identify the black material

Ah, we are Coppercoated, and had similar black deposits on our stern peardrop-would 4/5 coats + original Northshore copper gelcoat get the concentrations up near the above?

 

[VicS]

Ah, we are Coppercoated, and had similar black deposits on our stern peardrop-would 4/5 coats + original Northshore copper gelcoat get the concentrations up near the above?

Not to M/10 shouldn't think but I'd certainly be suspecting the coppercoat as a possible cause of a slowly forming deposit from a more dilute solution.

Id expect the phenomenon to be well documented though.

 

[Tidewaiter2]

Not to M/10 shouldn't think but I'd certainly be suspecting the coppercoat as a possible cause of a slowly forming deposit from a more dilute solution.

Id expect the phenomenon to be well documented though.

Thanks, VicS, probably does it like that at dead low water in the hole in the mud in our berth.

 

[slipknot]

So unlikely to be at the levels of concentration in my situation. The boat is always afloat.