Презентация на тему Zinc coatings

present is practicaly based on the research work I’m

going at the department of “Innovation materials and corrosion protection”. The research in this field is of great value for corrosion protection of steel and iron constructions. I’m particular interested in zinc coatig for corrosion protection.

of metal (usually iron or steel) with zinc coating

to protect against corrosion by dipping the product in a bath of molten zinc at a temperature of about 460 °C.

Electrochemical method
application of zinc on the surface was done under the current from solutions

galvanizing process, also known as general galvanizing, produces a

zinc coating on iron and steel products by immersion of the material in a bath of liquid zinc. Before the coating is applied, the steel is cleaned to remove all oils, greases, soils, mill scale, and rust. The cleaning cycle usually consists of a degreasing step, followed by acid pickling to remove scale and rust, and fluxing, which inhibits oxidation of the steel before dipping in the molten zinc.

sodium hydroxide)
Rinsing in water
Pickling
Rinsing in water
Flux solution ( NH4Cl,

ZnCl2, glycerin)
Drying
Zinc bath
Cooling and inspection

method of zinc coating. Well known two groups of

electrolytes for electrochemical zinc coating.
Zinc is anodic protector to steel or iron surface, because it has small compared to steel electrochemical potential. Zinc has good protection properties for steel constrictions in soft atmospheric envirament.

g/l
NH4Cl (NaCl) 1-3 g/l
(NH4)2SO4 10-12 g/l
H3BO3

15-25 g/l
brightening agent additives
рН 4,5÷5,5
ZnS04 80-120 g/l
NH4Cl (NaCl) 180-220 g/l
H3BO3 15-25 g/l
brightening agent additives
рН 4,5÷5,5

Alkaline electrolyte
ZnO 40-80 g/l
NaCN 80-90 g/l
NaOH 40-50 g/l
Brightening agent additives
pH 10-11

the preparation, high allowable current density and the current

output,
coatings with high gloss, low nastorajivaet steel base

high concentration of chloride ions is highly corrosive electrolyte

Alkaline electrolytes
Very toxic electrolytes
A serious disadvantage of cyanide electrolytes galvanizing (without additives)
is significant hydrogenation of steel parts, which leads to a sharp deterioration
mechanical properties of parts after coating: reduces the ductility, increased fragility

zinc coatings in sleel surfaces and constructions are very

interesting and have a great value for specialists from galvanic plants, professors from our university and students from departments of electrochemical industry and corrosion protection.