maintenace

1. Preventive
Maintenance
Vol. 1
Preventive
Maintenance
Vol. 1
1
2
3
4
Base Metal
Chrome Plating
Corrosion in white
Base Metal
Chrome Plating
Melting of CoatMelted Chrome
Base Metal
Chrome Plating
Iron Oxide (Red Rust)Melted Chrome
Base Metal
Chrome Plating
Extrusion of coat
Invasion of Rust
In the initial stage, the surface of coating will turn to
white (It is visible). This is called "Chrome," and it means
the chrom is in initial corrosion.
If the initial corrosion is progressed, the thickness of
coating will decrease because the chrome gets melted.
If the corrosion is progressed more, the plating is
completely removed, and the base metal will be
exposed. Consequently, the base metal gets rusted and
turns to red color due to iron oxide (Fe2O3).
Once the red rust is observed, the water and moisture
get into the base metal, and the created rust is
penetrated through the base metal. The penetrated rust
will push the plating up to extrude the coat.
HYDRAULIC CYLINDER
Save cylinder rods from corrosion
2. Mechanism how cylinder rod gets rusted
How do you think the cylinder rod get rusted?
1. Rust on Cylinder Rod
The cylinder rod which we introduce below is an
example of rust exposed to rain and salt wind for a long
period. Because the crane owner remained the cylinder
extended for the period under the condition, the cylinder
gets rusted. If the rod is rusted and if the crane driver
extends or retracts the cylinder, the rusted portion will
lead damaging the oil seal which causes oil leakage as
seen in the pictures below. In this case, the replacement
of oil seal and retreatment of cylinder rod should be
performed, and it will cause long down-time of machine.
If red rust is observed on the surface of cylinder rod, it
causes damages of sealing for cylinder.
Consequently, oil leakage occurs, and the sealing should
be replaced. In addition, extrusion of plating seems to
be caused by invasion of rust due water, but we can
not identify the exactly portion from which the water
or moisture comes. Therefore, in this case, re-coating
of cylinder rod, replacement of cylinder rod or cylinder
assembly will be required.
Most of mobile cranes have hydraulic cylinders, and they are used for each corresponding
functions such as Boom Hoist, Telescopic, Gantry Hoist, Crawler Extension/Retraction and
etc. As you know, rods of these cylinders are exposed to rain and wind at most of the time, so
the cylinder rods can get rust even if the rods are plated with Hard Chrome. In other words,
maintenance of cylinder rod is mandatory.
Location on Cranes Cylinder Rod Without Maintenance for a Long Time Oil Leakage due to defect on seal

2. Global Service Department
740, Yagi, Okubo-cho, Akashi-shi, Hyogo, 674-0063 JAPAN
TEL: +81-78-936-1408 FAX: +81-78-935-5240
For further information, please contact...
Preventive Maintenance Vol. 1
Hydraulic Mobile Cranes
Where What How
When
Each Hydraulic Cylinder
Exposed Surface of Rod
Best Grease for Cylinder Rods
General Purpose Grease
Every 1 month or every 100 hour
With brush or spray
Sample
3. Cause of corrosion of Chrome and red rust
Corrsion is one of the chemical reactions (oxidation)
on surface of plating (Chrome) due to environmental
factors and/or chemical factors in ambient circumstance.
In chemical study, Chrome tends to oxidize much easier
than Iron, so you would say, “It is useless to plate the
base metal with Chrome.” However, Chrome reacts with
oxygen arbitrarily, and the chemical reaction creates
“Oxide film” which is very thin. The film prevents the rod
from the rust as well as oil film on the surface of cylinder
rod. Because of the oxide film of Chrome, the plating
does not get rust easily. However, in the following
occasions, the oxide film will get damaged, and the plate
of Chrome will also get corrupted.
Consequently, the base metal gets rusted to have red
rust (iron oxide).
1) When acid element in rain sticks on rod, the acid
will melt the plating.
2) When chloric element in sea water sticks on rod,
the element melts the plating in chemical reaction.
3) When chemical in the air such as sulfuric acid
sticks on rod, the chemical reaction melts the plating.
[jobsite with chemicals such as chemical plant and
surroundings]
4. To prevent the corrosion of Chrome and red rust on base metal
On hydraulic cylinder, operation in extension and
retraction will create micro oil film on the surface of
cylidner rod, so if you leave cylidner rod extended
(derricking in and/or tele-out) for a long time, the oil film
will be removed by acid in rain. Consequently, if the acid
sticks on the surface of cylinder rod, it causes corrosion
of Chrome and red rust on base metal. In this occassion,
please follow the operation below.
On machines working near beach, port or cliff, red rust
can be observed much earlier than machine wokring in
land. If your machine is in those occassions, maintain
the cylinder rods in shorter period than normal in order
to extend the service life of hydraulic cylinders.
PMV01_2013-R1
1) In long term storage, retract all the hydraulic cylinders
fully.
2) If surface of rod is exposed, apply sufficient grease or
other oily material to cover the rod.
3) Protect the exposed rod with soft cloth including oil.
These maintenance job extends the service life of
hydraulic cylinders.
Long term storage
with boom derricked
Exposed surface of cylinder rod in
full retraction