Rust forms in mission-critical facilities when iron combines with oxygen and water in the presence of an electrolyte like moisture. High humidity above 50% RH causes corrosion to grow exponentially by providing the electrolyte. Maintaining humidity between 45-55% RH prevents rust and dendrites by eliminating electrolytes while avoiding static electricity. Properly sealing facilities with vapor barriers controls humidity and prevents infiltration that can cause equipment failures.

1. Preventing
rust in your
Mission-Critical
Facilities
B y J o e S o r o k a

2. Preventing rust in your
Mission-Critical Facilities
As technology reaches into every corner of our world, the
importance of, and reliance on, your mission-critical facility
reaches new heights and there is no place in your facility
for rust. Rust is the common name for a very common
compound - iron oxide. Iron oxide, the chemical Fe2O3,
is common because iron combines very readily with
oxygen. Iron (or steel) rusting is an example of
corrosion, an electrochemical process, requiring an
anode, electrolyte and a cathode. The anode is a
piece of metal that readily gives up electrons, the
electrolyte is a liquid that helps electrons move and the
cathode is a piece of metal that readily accepts
electrons. When a piece of metal corrodes, the
electrolyte helps provide oxygen to the anode. As
oxygen combines with the metal, electrons are
liberated. When they flow through the electrolyte to the
cathode, the metal of the anode disappears, swept
away by the electrical flow or converted into metal
cations in a form such as rust.
When a drop of water hits an iron object, two things
begin to happen almost immediately. First, the water, a
good electrolyte, combines with carbon dioxide in the
air to form a weak carbonic acid, an even better
electrolyte. As the acid is formed and the iron
dissolves, some of the water will begin to break down
into its component pieces - hydrogen and oxygen. The
free oxygen and dissolved iron bond into iron oxide and
in the process, free electrons. The electrons liberated
from the anode portion of the iron flow to the cathode,
which may be a piece of metal less electrically reactive
than iron, or another point on the piece of iron itself.
2

3. The chemical compounds found in liquids like acid rain,
seawater and the salt-loaded spray from snow-belt
roads make them better electrolytes than pure water,
allowing their presence to speed the process of rusting
on iron and other forms of corrosion on other metals.
In your mission-critical facility it is important that you
keep the room clean so the dust and dirt does not
increase this process. Along with keeping your room
clean, it is important that you are aware of the cleaning
products you are using in your facility. Ammonia based
cleaning products should not be used in your mission-
critical facility since the caustic property will facilitate
the formation of rust and dendrites.
The term dendrite comes from the Greek word
"dendron,” which means a tree. This description is
appropriate because we often describe the form and
structure of a metallic dendrite as that of a tree. These
tiny metallic snowflakes grow in your mission critical
facility and just as rust, they need an anode, cathode
and an electrolyte. Printed circuit boards (PCBs) can
suffer from a variety of problems if the surface is
contaminated with electrically conducting materials.
When combined with moisture, contamination results in
a lowering of resistance between tracks and pads that
can lead to corrosion of metals. It can also result in the
formation of metal filaments, which grow between pads
or tracks on rigid or flexible circuits and between
oppositely charged metal terminations of components
or between the pins of connectors. The essential
conditions required for this are a combination of ionic
contamination, moisture and an applied voltage.
The build up of rust and dendrites will decrease
equipment reliability and increase the maintenance
required. So how do we prevent this by removing the
anode, electrolyte and cathode from your mission-
critical facility? Since removing the anode and the
cathode from our facility would leave us with an empty
room, we must eliminate the electrolyte.

4. The US Marine Corps has conducted extensive
research on corrosion prevention and by maintaining
relative humidity (RH) below 50 percent, adverse
effects of humidity are eliminated, including rust,
mildew, mold and moisture. Above 50 percent RH, the
rate of corrosion growth shifts from linear to
exponential; however, we cannot just drastically reduce
the humidity in the facility. When relative humidity
levels drop below 35%, static electricity can build up on
surfaces and in clothing, ready to discharge at a single
touch. Static discharge can destroy microchips, pit
surfaces, ignite volatiles and generally make hand-
shaking a nasty experience.
With static electricity on one side and rust, dendrites
and condensing liquids on the other side, it is important
that we maintain proper humidity in your facility. For
this reason, it is recommended that you maintain the
humidity in your facility between 45% - 55% RH. In
order to provide a stabilized environment, you need to
have, a humidification system, a dehumidification
system, sealed envelope and a control and monitoring
system.
Controlling humidity in your mission critical facility is
like controlling water flow in a water level. When
humidity outside is greater than in your facility, the
humidity wants to equalize and it will seep in every little
crack and hole until the two spaces are balanced. On
the other hand, when the outside humidity is very low in
your facility, your humidifiers want to equalize the
outside and the humidity will seep out of those cracks
and holes to try to bring up the outside humidity. When
the size of the cracks and holes in your facility are
larger than the capability of your humidification and
dehumidification systems to over come, you will then
loose control of the humidity in your environment. By
properly sealing your facility, you will improve humidity
control and reduce your energy consumption.

5. Sealing the data center envelope starts with having an
adequate vapor barrier from slab to slab. Starting with
the floor, you need to properly seal the concrete with
an approved vapor barrier sealer. Sealing the floor will
prevent the seepage of humidity and will help to
eliminate the build up of dust. Concrete dust damage
often occurs when materials are whirled up in the air
and unintentionally end on surfaces of technical
equipment. This secondary damage ranges from
oxidation, excessive wearing of moving parts to
overheating and potential electronic circuits failures
due to shorting.
Once you are assured that your floor is properly sealed
and cleaned, make sure the walls are painted or
covered with an approved vapor barrier. This vapor
barrier should extend slab to slab. The walls below the
raised flooring and above the ceiling tiles also need to
be sealed. All of the wall penetrations need to be
sealed with a proper material. In most cases, you will
be required to seal these wall penetrations with an
approved fire stop material. This requires that you take
your flash light and look under the raised flooring and
inspect all of the walls surrounding the perimeter of
your data center. Once you have inspected and
corrected all of the wall penetration, inspect the walls
above the ceiling tiles and perform the necessary
repairs.
Now that you have your floors and walls sealed, it’s
time to inspect the roof. Make sure that just like the
floor and walls, your roof is sealed and all roof
penetrations are properly sealed. In some cases the
suspend ceiling is used for the top of the vapor barrier.
When this is done, it is important that the ceiling tiles
are rated to be used as a vapor barrier along with all of
the lightning fixtures.

6. Rust in your mission-critical facility is an indicator that
you have other problems. Make sure you get a handle
on your humidity control by ensuring that your
humidification and dehumidification equipment are
working properly and the room is properly sealed. You
should keep your data center clear of debris and dirt,
cleaning not only what your customer sees, but below
the floor and above the ceiling tiles.
Joe Soroka is the Director of Technical Services at Lee Technologies. Lee Technologies has
been providing customers with full lifecycle solutions to their mission-critical facilities since
1983. Joe has been working in the mission-critical facility industry over the past 20 years
and has consulted for fortune 500 companies on maintenance, reliability, failure analysis,
and commissioning of their facilities.You may contact Joe at jsoroka@leetechnologies.com or
(703) 968-0300.
Lee Technologies has been providing high-availability infrastructure products, services and
solutions for mission-critical environments since 1983. For more information on Lee’s entire
line of infrastructure solutions, call 877-654-9662 or visit www.leetechnologies.com.
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