[kavin011]

Dear All,

      Iron wire has zinc coating ( safe from rust),how we  can measure the Zinc coating percentage of that wire. The procedure as follows(gravimetric method): In internet i searched some procedure as below.

Reagents:
The stripping solution shall be hydrochloric acid with a concentration of 1.13 g/mi to 1.19 g/ml by density to which an appropriate inhibitor is added.Dissolve 3.2 g of antimony (III)Chloride or 2 g of antimony (III)oxide in 500 ml concentrated hydrochloric acid (1.19 g/ml).Dilute this solution with distilled water to 1 litre.Hexamethylenetetramine,formaldehyde or any other suitable inhibitor may be used.
Note: It is recommended that preference be given to inhibitors which do not contain antimony.


1) actually Zn coating  is dissolved in Hcl acid (37 %) ,but why these many compounds we need to use like SbCl3 /Sb2O3/C6H12N4/HCHO ?

2) My another doubt is after removing the Zn coating from iron , that iron also will dissolved into Hcl? thats why they using these many compounds? please clarify because Fe also easily dissolved into Hcl. If yes means kindly let me know  the occuring chemical reactions from that procedure.

[chenbeier]

The inhibitor is only one compound, either antimony , hexamethylentetramine or formaldehyde, it prevents the iron to dissolved in my understanding.
The result is then: weight before stripping zinc and weight after.

More acurate would be to dissolve a weight piece of the wire without adding inhibitor and do an analyse  for zinc.

If the thickness is important then prepare a micro section: mould a piece in a resin and grinde and polish it . Check with a microscope.