Piston Rods

The piston rod is the key component to any hydraulic ram and probably the most prone to damage.
The rod must be the right length and diameter to avoid buckling and strong enough to take the load.
What I wish to focus on is the surface finish.
Many rods are made from high grade carbon steel and flash chromed. Often you can buy the material straight off the shelf and ready to machine the ends.
The chrome is used for its hardness and wear ability. Under the microscope it will appear like a crazed plate and if subject to a prolonged wet environment the chrome will soon show signs of rust and bubbling up of the plated surface.
On marine applications I once used stainless steel with chrome on top. The stainless was soft but corrosion resistant while the chrome is hard and porous. A great combination you might think. After a few months we discovered tiny marks in the chrome. Under a glass it appeared like a small crater with a very sharp edge.
The chrome was being pulled from the rod and we put this down to the electrolytic action of the seawater. We installed a sacrificial anode with little improvement. Eventually we replaced the rods with plain stainless steel. We suffer a little extra wear but keep the seals in good order.
Also do not make your rods with a too perfect finish. High polished rods will wear the seals due to reduced lubrication.
There are lots of other interesting things about piston rods but I just thought of a couple but please tell us about your experiences.
Cheers
Bob
Read more on www.hydraulicbrain.com