Years ago I was at a seminar about hyd rod materials sponsored by Fluid Power Society.
It was an in-depth discussion about nitrited vs industrial hard chrome plated.
Several points were brought up about nitrited rods.
The Nitrite process is cheaper to produce hyd rods but removes the possibility to produce induction hardened product due to the intense heat and cool process of nitriding will anneal the induction hardened rod material. Industrial hard chrome does not effect the preprocessed induction hard surface when plating.
Nitrite manufacturers boast about corrosion protect but the salt spray test they use is not a real world test. Under a salt spray test high pressure salt sprayed the nitrite wins under those conditions but chrome plating in routine use gets its corrosion protection from being retracted into the cylinder to get bathed in oil, the chrome plating under a microscope is porous (the reason they corrode when not in use). CP rods being used routinely will out last nitrite.
Nitrite hyd rods cannot be polished during a repair without losing its outer coating. CP rods can be polished easily with no harm.
Two material tests on steel is tensile and yield strength. Yield strength is exceeded when steel bends under stress and stays bent. Tensile strength is exceeded when it snaps. Nitrided hyd rods have the tension and yield strengths near the same numbers. Chrome plated hyd rods will yield before they snap.
This is a big reason why you don’t see hydraulic rods on cranes, manlifts and bucket trucks with nitrided hyd rods. OEM’s would rather have a hyd rod bend during an overload instead of snapped causing severe personal and property damage. I have personally seen many nitrited rods that snapped, laying them out on a table it’s clear they snapped without a noticeable bend.
We build replacement hyd rods for many different industries in our busy hyd shop and I can say more than 50% of cylinders with nitrited hyd rods need replacement because of corrosion. We always change them back to hard chrome plated material with absolutely no issues.
Years ago one of my employees went to a local farm fair (Deerfield Fair, Deerfield NH) and two large John Deere distributors had machines on display. On one side of the road were all yellow industrial machines (excavators, dozers, backhoes etc). On the other all green JD ag equipment. My guy asked the salesman on the green side “why doesn’t JD use chrome plated hyd rods on the green equipment?”. His response was “Oh, it’s much better”. My guys response, “OK then why are all the rods on the yellow equipment chrome plated?”
