Hard chrome is porous. It will retain lube in these micropores but over time in moist areas they will rust. Here is advice for farmers from Louisiana State Extension Services. The tend to have a rather moist climate down there.
The solution to this problem is to prevent rust and pitting. There are three ways to accomplish this, and it is possible to use more than one of these approaches simultaneously. The best way to avoid corrosion and pitting of the cylinder rods is to store the implement with the cylinder rods retracted. If the rods are retracted, the sensitive plated surface of the rod will be inside the cylinder, immersed in hydraulic fluid and thus fully protected. Unfortunately, it is not always possible to store equipment with the cylinders retracted. In some cases, the cylinders must be extended to unhitch an implement or must be extended to park the equipment. Another way to reduce the chance of corrosion is to park equipment with hydraulic cylinders inside a building where the cylinders are protected. This will significantly reduce corrosion and pitting, although humidity and condensation can still occur in some storage sheds. A final method of protecting cylinders is somewhat less effective but can be used in all situations. The exposed cylinder rods can be coated with heavy grease whenever the equipment will not be used for a few weeks or longer (Figure 2). The grease should be as heavy and sticky (tacky) as possible. Wheel bearing grease is better for this purpose than general chassis grease because it tends to be tackier. A heavy coat of grease will provide several months of protection, but for a machine used only one season a year, it may be necessary to renew the grease every three to four months.
