bajo
Well-Known Member
Please would SS 316 be ok for manufacturing a 1inch diameter prop shaft approx 42 inches in length for a 9hp 1GM 10 engine .What is usually preferred.
prop shaft material
- Thread starter bajo
- Start date
swampthing
Well-Known Member
316 is the usually accepted marine grade
brianhumber
Well-Known Member
Warm waters such as Barbados tend to encourage corrosion so only best steel advised.
AISI 316/BS316s31 is recommended because they contain nickel and molbdenum to improve corrosion resistance. However 316 can still suffer from crevice and pitting in oxygen starved applications so is not a fit and ignore material - You should pull your shaft at regular intervals.
Brian
AISI 316/BS316s31 is recommended because they contain nickel and molbdenum to improve corrosion resistance. However 316 can still suffer from crevice and pitting in oxygen starved applications so is not a fit and ignore material - You should pull your shaft at regular intervals.
Brian
charles_reed
Well-Known Member
In fact
contrary to what you'd expect, anaerobic corrosion is frequently faster in 316 at 4-6C.
Certainly the great enemy of propshafts is anaerobic corrosion (shouldn't be machined to produce pockets for crevice corrosion), for that reason, though it's about x15 the price, some prefer (such as MoD) bronze.
If you're interested I'll try and obtain the spec from the Materials dept at Soton.
contrary to what you'd expect, anaerobic corrosion is frequently faster in 316 at 4-6C.
Certainly the great enemy of propshafts is anaerobic corrosion (shouldn't be machined to produce pockets for crevice corrosion), for that reason, though it's about x15 the price, some prefer (such as MoD) bronze.
If you're interested I'll try and obtain the spec from the Materials dept at Soton.
Tranona
Well-Known Member
Re: In fact
316 is fine. Just make sure that, if it is a replacement that it is 1 inch and not 25mm, otherwise you will have to replace everything, coupling, cutless and prop! Agree regular inspection is advisable, but if the boat is used regularly to keep flow of water through the stern tube crevice corrosion should not be a problem.
316 is fine. Just make sure that, if it is a replacement that it is 1 inch and not 25mm, otherwise you will have to replace everything, coupling, cutless and prop! Agree regular inspection is advisable, but if the boat is used regularly to keep flow of water through the stern tube crevice corrosion should not be a problem.
boatmike
Well-Known Member
Re: In fact
Agreed. Crevice corrosion is only a problem where water supply (and therefore oxygen) is not flowing freely and dead spots occur. It this situation either a Duplex stainless, Monel or Bronze can be used but they are all vastly more expensive and 316 is usually fine.
Agreed. Crevice corrosion is only a problem where water supply (and therefore oxygen) is not flowing freely and dead spots occur. It this situation either a Duplex stainless, Monel or Bronze can be used but they are all vastly more expensive and 316 is usually fine.
boatmike
Well-Known Member
Re: In fact
Glad you did! I would probably have tied myself in knots trying to explain that and would have got some of it wrong! Have used Duplex and Superduplex A219 for shafts where they meet difficult corrosion conditions. The "City Cruisers" boats that some may have been on up and down the Thames were a case in question. They had Cummins engines with very long shafts down a stern pipe with no water flow through. The 316 shafts in those conditions pitted like the craters of the moon! We replaced them with A219 shafts and diverted some of the engine cooling water out through the shaft tubes. Problem solved. Horrible stuff to machine though!
Glad you did! I would probably have tied myself in knots trying to explain that and would have got some of it wrong! Have used Duplex and Superduplex A219 for shafts where they meet difficult corrosion conditions. The "City Cruisers" boats that some may have been on up and down the Thames were a case in question. They had Cummins engines with very long shafts down a stern pipe with no water flow through. The 316 shafts in those conditions pitted like the craters of the moon! We replaced them with A219 shafts and diverted some of the engine cooling water out through the shaft tubes. Problem solved. Horrible stuff to machine though!
