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I. Introduction

Alkaline non-cyanide zinc (NCZ) plating has gained commercial success
for its low cost of operation, ability to produce cosmetically acceptable
deposits, environmentally friendly electrolyte, and ability to plate with
excellent distribution over complex geometry. NCZ chemistry is used
in manual rack and barrel plating lines as well as large programmed
automatic machines. With increasing environmental restrictions and
competitive pricing, alkaline non-cyanide zinc will continue to grow
replacing cyanide processes and in some instances the more costly acid
Zinc chloride process.

II. Pre-treatment

Cleaning
The general rule of thumb for NCZ plating on steel is that the cleaning cycle
shall be at least as good or preferably better than what is considered good
for bright nickel and acid zinc plating. This typically will require the use
of soak cleaning, electrocleaning, acid activation, electroclean, a mild
activation, an alkaline pre-dip, and then NCZ plate. This extensive
pre-treatment is required due to the absence of cyanide in the electrolyte.
The work must be free of oils and smut prior to plating if uniform, bright,
adherent deposits are to be obtained.

Acid Activation
The proper use of acid pickles is essential in NCZ plating. In order to
ensure a bright, uniform, adherent deposit, all heat scales, smut, or other
surface defects must be eliminated. Due to the high hydrogen overvoltage
of the NCZ electrolyte, zinc plating will not initiate over heat scales
or carbon that has been brought to the surface.

Pre-Dip
The use of the alkaline pre-dip is unique to NCZ plating. Iron contamination
in the bath will result in poor chromating and with some brightener
systems, blistered deposits. The pre-dip should contain 2 oz/gal
of ENTHOBRITE® 4211 water conditioner to chelated soluble iron,
and 4 oz/gal caustic soda to precipitate any iron dragged into the plating bath. To avoid drag-in of chelated iron, the last electrocleaner should
be chelate free.

Plating Zinc Die Cast
The ENTHOBRITE NCZ 916 A, B & 966 C system has proven to be
excellent for producing bright, adherent deposits On zinc die cast. The recommended cycle is as follows:
    1. Soak Clean, ENPREP® 72 SE, 180, or 182.
    2. Electroclean Anodically 15-20 ASF, ENPREP 72 SE, 285, or 288.
    3. Counter-Flow Rinse.
    4. Acid Activation, ACTANE 73 or ENPREP 340.
    5. Counter-Flow Rinse.
    6. NCZ Electroplate.
 
 
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