What causes a propeller to go pinkish in colour?

[Carmel2]

Is it time to start to thinking about changing it, or no problem?

 

[graham]

Is it time to start to thinking about changing it, or no problem?

Usually means the zinc is gone from the metal due to corrosion and electrolisis. Eventually bits will start breaking off the edges.Before replacing it check your anodes are correctly installed or the new one wont last long.

If you tap it with a hammer it should have a metalic ring not a dead thump.

 

[Carmel2]

Thanks for that, Would reverse polarity form shore power be a contributing factor?

 

[vyv_cox]

It's dezincification, there are some examples on my website here. A propeller is quite a large casting that is not going to fail catastrophically because of a small amount of corrosion. Polish it back to assess its condition. If pieces are breaking off the trailing edges then think about a replacement. Otherwise, monitor it, as said by tapping it and by visual inspection.

 

[vyv_cox]

reverse polarity wont cause dezincification but a leak to earth on a nearby boat in the marina could give you trouble. A galvanitic isolator will prevent this.

True, but dezincification occurs quite happily without the influence of externally applied voltage.

 

[Carmel2]

Thanks for all this!

 

[VicS]

agreed, it can have many causes, its just a matter of reducing them,

a bit of thread drift; my main sheet blocks were on aluminium supports, not "connected" to anything except a grp deck, electrically the main sheet track was isolated - they dissolved, the stainless replacements I made are fine. The problem the OP has is that the prop is always in electrolyte. In another life I found that DZR material is not a guarantee that there will be no dezincification, the failure rate of DZR components was lower than brass but not by much, bronze was better but not always, often hard to know exactly what "bronze" we were buying suppliers often couldn't/wouldn't tell us, it's bronze OK! is what we got. some worked some did nt even the colour was not a consistent guide but generally the redder the better.

Bronze does not dezincify .. it does not contain zinc

Manganeses bronze contains zinc.. it is really a brass and some suppliers even call it manganese brass .. it is used for props because it is resistant to sea water corrosion but in the wrong circumstances it can dezincify.

 

[penfold]

Bronze does not dezincify .. it does not contain zinc

Manganeses bronze contains zinc.. it is really a brass and some suppliers even call it manganese brass .. it is used for props because it is resistant to sea water corrosion but in the wrong circumstances it can dezincify.

It's used to make props because it's cheap, tough, easy to cast and resistant to corrosion compared with other brasses. It's a compromise as ever.