221 bright alkaline cyanide-free zinc plating process
2017-12-05
code：221
name：221 bright alkaline cyanide-free zinc plating process
221 process is the newest cyanide-free zinc plating technology, it overcomes the problem of embrittlement even in mirror bright and thicker deposits. the metal distribution and the temperature tolerance of the electrolyte are more perfect .
①mirror bright coating
221 brightness is higher than the cyanide zinc plating process and conventional alkaline zinc plating process, and comparable to acid zinc. passivating without fogging haziness.
②avoids yellowing problem of blue chromate
221 alkaline zinc after blue chromate, the coating is deep blue, comparable to acid zinc.
③not hazy of yellow trivalent chromating
221 alkaline zinc coating is clear and transparent; the cyanide zinc plating coating is tend to fogging be hazy.
④high bright deposit without embrittlement
⑤high throwing power and even metal distribution
high throwing power, and even thickness of coating, greatly saves the consumption of zinc ingot, saving 25-40% than acid zinc, 15-30% than cyanide zinc plating.
left fig: the thickness of outer coating is 25μm, inner is no less than 17μm221工艺
221 process
⑥ tolerance to high temperature
when the bath temperature is 50℃, the coating is still mirror brightness bright.
⑦ excellent covering power
the covering power is superior to cyanide zinc plating and acid zinc.
⑧super adhesion to passivation film
the adhesive force of 221 alkaline zinc coating is greater than acid zinc, and is comparable to cyanide zinc plating.
⑨wide current operating range
when the current is 6a in the hull cell, the whole specimen panel only has 0.5 cm burnt, when 0.2a, the specimen panel can be bright.
⑩strong impurity tolerance
□the bath can be prepared with ordinary and tap water ,no need for 99% high purity alkaline hydroxide and pure water.
□strong tolerance of impurity from pretreatment, the test is as follows:
comments: it is better to carry out the pretreatment completely, and use high purity alkaline and pure water to prepare the cell bath.
⑪stable bath
⑫key points of maintenance
make-up:
221 a brightener 5-25ml/l,
221b carrier 0.5-1.5ml/l,
221c purifier 0.5-1.5ml/l.
consumption:
221a brightener 100-200ml/kah,
221b carrier 20-70ml/kah,
221c purifier 10-20ml/kah.
