The principle of galvanizing technology overview and main classification
(a) overview
Compared with other metals, zinc is relatively cheap and easy to a metal plating, belongs to the low corrosion electric plating. Is widely used to protect steel parts, especially from atmospheric corrosion, and used for decoration. Plating technology including tank (or hang) plating, barrel plating plating (suitable for small parts), automatic plating and continuous plating (suitable for wire, strip).
At present, the domestic classification according to the plating solution, can be divided into four categories:
1. The cyanide zinc plating:
Because (CN) is a highly toxic, environmental protection for cyanide used in electric galvanized puts forward strict limits, constantly promote reduce cyanide and to replace cyanide plating solution galvanized system development, requires the use of low cyanide plating solution (micro cyanide).
Adopting this process after the plating, product quality is good, especially the color plating, after passivation colour keeps good.
2. The zincate galvanized:
This craft is evolved by cyanide zinc plating. At present domestic formed two factions, respectively is:
A) wuhan material confirmed by "DPE" series
B) radio and television of the "DE" series
Belong to alkaline zincate galvanized additive; PH value of 12.5 ~ 13.
Adopting this technology, coating for cylindrical lattice structure, good corrosion resistance, suitable for color galvanized.
Typical formula:
NaOH -- -- -- -- -- -- -- -- -- -- -- -- -- 110 ~ 120 g/l
ZnO -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 11 ~ 12 g/l
94 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 5 ~ 7 g/l
For the product code 94 is "DPE - Ⅱ" and the combination of ethanolamine.
Note: the product out of the groove - > wash - > after the light (nitric acid and hydrochloric acid) - > wash - > passivation - > washing - > washing - > hot dry - > drying - > aging treatment (oven within 80 ~ 80 oc.
3. The chloride galvanized
This technology is widely used in electroplating industry, the proportion is as high as 40%.
Generation after passivation (LanBai) can zinc chrome (equivalent to that of chrome plating), especially after plus water soluble varnish, it is hard to recognize the layman is galvanized or chrome plated.
This process is suitable for white passivation (LanBai, silvery white). When customer has no special requirements, it is best to choose silvery white passivation (color keep relatively stable).
Typical formula:
KCl -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 180 ~ 220 g/l
ZnCl -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- - 65 ~ 75 g/l
H3BO3 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 25 ~ 30 g/l buffer (PH) : 5 ~ 5.5
CI - 87 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 15 ~ 20 g/l (brightener)
4. Sulfate zinc
This process is suitable for continuous plating (wire, strip, simple, rough large parts and components). Low cost.
Typical formula:
ZnSO4 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 300 ~ 500 g/l
H3BO3 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 25 ~ 30 g/l. PH value: 4.5 ~ 5.5
Sulfur, zinc -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 15 ~ 20 g/l (brightener).
