I have a piston made of anodized aluminium and stainless steel with nitrile seals which I need to connect hydraulically to our system which mainly consists of silicone rubber with polycarb and acrylic parts, but I'm having problems finding a fluid which will lubricate the pistons without damaging the seals or any of the materials in the system.


The piston and piston seals (nitrile rubber) are all pretty corrosion resistant but even so the manufacturer doesn't recommend using water in them and can't say what the effects would be, other than washing the existing lubricant out - I don't know how much of an issue water would cause?

As for oils:

Mineral oil attacks the silicone rubber.

Silicone oil apparently 'hydrates' the silicone rubber, so softens and distorts it.

PE-glycol based automotive brake fluid is fine for the silicone and pistons but cracks the acrylic and polycarb.

Vegetable oils are fine for all parts chemically, but I was always taught not to use veg oil as a lubricant and this question seems to answer why - i.e. the veg oil attracts dirt and 'gums up'.

So my questions are:

  1. Would water be suitable as a lubricant for the piston?
  2. If its a closed system and the oil is changed regularly, would vegetable oil (e.g. corn oil) work?
  3. Any suggestions for something to avoid all the above issues?

Many thanks all

  • 1
    $\begingroup$ Use materials and seals made of materials that can all have one lubricant... this seems to be a design made of disparate parts that has few solutions “as is”... $\endgroup$
    – Solar Mike
    Oct 23 '18 at 20:50
  • $\begingroup$ @SolarMike do pistons exist for use with water do you know of? $\endgroup$ Oct 23 '18 at 21:09
  • $\begingroup$ There are many pumps with pistons designed to pump water.. $\endgroup$
    – Solar Mike
    Oct 23 '18 at 21:12
  • $\begingroup$ @SolarMike If you could please put up an example of one as a formal answer, I will mark it the answer $\endgroup$ Oct 26 '18 at 17:40

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