Chemical Corrosion; Stress Corrosion; Cleaning; Electricity - NUVE NF 1200 User Manual

6.3.1. Chemical Corrosion

This type of corrosion is caused by chemical reactions. The electrolide liquid on the surface of the
material is the main cause of the chemical reaction. If that electrolide liquid is allowed to stay at
the surface, corrosion occurs. First, discoloration appears and then the metal pittens. Aluminum
easily reacts with the ionic solutions.
The other causes of corrosion are as follows,

Chemical vapors in the laboratory environment which dissolve in the water on the rotor (in
refrigerated centrifuges)

Corrosive liquids which overflow from overfilled and unsealed tubes. (the liquids which spread
out during centrifugation)

Contaminated and non-cleaned buckets, tubes and bottles.
NOTE: If the centrifuged samples are corrosive, only rinsing with water is not sufficient. The
residuals dissolve in the water and humidity on the rotor and in the buckets.
NOTE: Some particles may stick to the tubes, buckets and adapters. These particles crash and
do harm to anodized surface during centrifugation and ease the occurrence of
corrosion.
6.4.

Stress Corrosion

This type of corrosion is caused by the force of the centrifugation of the corrosive chemical which is
already in contact with the alloy. As the aluminum alloy contacts with the corrosive chemical, the
stress corrosion starts. This type of corrosion is even more dangerous than the chemical corrosion
as the effects of this corrosion are microscopic and very difficult to observe in the course of time.
The corrosive material is pushed against the aluminum alloy by the centrifugation "g" force during
the centrifugation. This situation causes the stress corrosion to occur more quickly than the
chemical corrosion does. Microscopic cracks occur under the force of the centrifugation.
Every centrifugation causes the aluminum rotor to be attacked by the chemical more and more and
eventually micro-cracks decrease the resistance of the rotor against the centrifugation force.
Fortunately, no crash occurs just after the first micro-cracks have appeared as the rotors are
manufactured according to the high safety limits.
The corrosion of the small amount of corrosive materials does not result in severe cracks but
weakens the mechanical resistance of the rotor in the course of time.
The rotor's places, buckets, buckets' edges and the base of the rotor should be checked regularly.
If needed, they must not be used until a specialist has checked them thoroughly.
6.5.

CLEANING


Disconnect the centrifuge before cleaning.

There is no need of daily cleaning unless a tube breakage occurs or any liquid spills.
6.6.

ELECTRICITY

Centrifuged at high voltages are present behind the panels. These panels are electrically
disconnecting Do not open the centrifuge
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