Copper-Plating Propellers

[MagnusS]

A yellow-metal propeller can be made of either a brass-related or a bronze-related alloy. In both cases, some minor amount of Cupper Ions leave the surface and stops the barnacles from attaching. BUT: As soon as a sacrificing anode is connected, it stops those Cupper Ions to be releases, and the barnacles will attach and grow.

It is only the seawater-resistant NiBrAl-alloys that are really good for seawater use, and for these alloys, no sacrificing anode is required. By this, they will release Cupper, and will not get much barnacles.

However, the brass-related alloys MUST have some form of sacrificing anode for protection, and as a result from that, they will get lots of barnacles.

In Sweden, SXK (Swedish Cruisers Organisation) have organized a series of trials where more than 30 different yellow-alloy alloys, both of the Brass and the NiBrAl-types, fixed blades and folding all have been electro-plated with Cupper to a thickness of about 0.2 mm, in combination with NOT using any Zinc Anodes.

Cupper is a little less noble than both the Brass:s, and the NiBrAl:s and since it surrounds these, no significant corrosion has been noted even for the Brass-oriented propellers (without Zinc anode).

So far the trials have been ging on for tree seasons without redoing the electro-plating. There has been no barnacles worth mentioning for any of the propellers during this timeframe, andd the treatment seems to last for at least a couple of more years still.