Cleaning on
the basis of EDTA, Demclean 94®
. The Demclean
94 ® cleaning solution is based on EDTA in pH neutral media. This approach
eliminates, not only iron oxides, yet also light oil, grease as well as
atmospheric contamination.
The rust (iron
oxides) is dissolved with the formation of a strong iron-EDTA complex. This
enables the pH to be enhanced after cleaning without the iron precipitating as
ferric hydroxide. Then neutralization the steel is passivated by dosing sodium
nitrite.
This implies
that only one solution is needed for pickling and passivation with less water
being released. The waste water released by this cleansing procedure could be
treated by biological water purification modified for EDTA processing.
Advantages: pH
neutral cleaning agent; passivation with the cleaning solution; less waste
water; not corrosive for other metals; time saving.
Disadvantages:
addition of chemicals during the passivation phase; unable to eliminate mill
scale; limited capacity for dissolving iron.
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