Business: Industrial
Getting Ideas for Energy Management Opportunities
2.3.10 Special processes
Thermal galvanization
For thermal galvanization, iron parts must be cleaned of grease, dirt, rust
and mill skins. They must be first degreased and passed through a mordant
bath, a flux bath and a drier. The mordant bath usually becomes polluted
by iron particles that migrate into the zinc bath. There, crystals of iron/zinc
settle on the product and on the bottom of the bath. Quality of the product
is impaired and frequent cleaning of the zinc bath is required. This results
in losses of zinc, and of productivity. A galvanizing foundry in the Netherlands
installed equipment for regeneration of the flux bath. In a reactor, chemicals
are added to the fluxing fluid to react with iron and convert it to iron
hydroxide, which is filtered out. The clean fluids are returned to the bath.
In addition, the on-site generation of chlorine for the iron oxidation was
replaced by the use of hydrogen peroxide, H2O2, which further saved electricity.
The payback was two years.
Electroless3 nickel-plating
A U.S. corporation developed a nickel-plating chemical plating process that
does not require electrical current. It uses a regenerative process technology,
based on a multi-compartment electrochemical cell, to control the pH of the
plating bath electrodialytically. Selectively, useful anions are returned
to the
bath. The new process also eliminated the expense of treating and disposal
of the
spent bath waste.
3 Electroless plating is the deposition of metal coating by immersion of metal
or non-metal in a suitable bath containing a chemical reducing agent. (McGraw-Hill
Dictionary of Science and Technical Terms, second edition, 1978).