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Friction reducer needed in heavy duty sliding joint in ocean

Basically I am building a device that will see high normal forces, but also must be able to slide relative to a fixed part (steel on steel, or stainless on stainless). The problem is that this will be in an ocean environment where it would be preferable to not use grease for a few reasons. One being the environmental impact, another is the maintenace required for a grease joint, and a third is sealing the grease joint from the environment. Can anyone suggest a coating that would greatly reduce friction, would last a long time without maintenance, and can withstand the ocean?

Any help would be greatly appreciated!

Chris Phelan
Mech. E. - Pennington, New Jersey
2004

Very little information, but perhaps you might consider an intermediate piece of hard nylon or Teflon instead of a coating. It will last much longer if properly designed, built and secured.

Guillermo Marrufo
Monterrey, NL, Mexico
2004

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Thanks for the idea! What more information do you need? Some more specifics: Hydraulic cylinders are being used in a application that requires multiple degrees of freedom. BUT the hydraulic cylinders can "see" little to no side loads. So, a joint with mulitple degrees of freedom must be created. A rod end would take care of the pivoting motion, but side to side and front to back motion has to be accounted for. Thus the slip joint. The catch is that the normal force that the slip joint will "see" is 300kN. With the coefficient of friction of a greased metal on metal joint, the slip joint wouldn't slip until after the hydraulic cylinder "saw" over 3 tons of force! So I am looking for a way to decrease the coefficient of friction with a substance that will withstand the aforementioned forces. Can teflon do this? Any other ideas?

Chris Phelan
- Pennington, NJ
2004

Either Teflon or hard nylon materials can withstand the force provided enough surface is designed to spread the load. Nylon 6 is better mechanically. With 30% glass fiber reinforcement at 68 degF has a creep resistance on the neighborhood of 500 PSI for an indefinite time. Teflon only goes up to 100. Obviously both have different sliding or frictional behaviour. Your plastic supplier can give you more data to properly design your joint.

Guillermo Marrufo
Monterrey, NL, Mexico
2004

Hi Chris,

As Guillermo says, Nylon is stronger than teflon but personally I'm not too keen on it as tfe has far better permeation properties and its frictional properties are far superior. His suggestion of going to the 'right' plastics' distributor makes a lot of sense ... but try also GOOGLE and type in .... "glass filled teflon" .... as there you should find some fast answers, too.

Consider the glass filled teflon for greater structural strength

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).
2004

Thanks for the help!

Chris
- Pennington, NJ
2004

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Electroless nickel Phosphorus High P content, i.e. 10% or more, followed by electroless nickel with PTFE codeposited would serve well.

Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics" [on Amazon or AbeBooks affil links]
           and "Plating ABS Plastics" [on Amazon or eBay or AbeBooks affil links])
2005