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Zinc and Chromium Analysis

2007

I received a chemical analysis for (Zinc clear Plate Type II class 1)ASTM B633 (tank test)
ZINC Analysis
Parameters Results
Zinc 2.5
NACN 6.96
NAOH 10.48
RATIO 2.57

Chromium TRI Results
Cromium 12.1%
PH 2.2

I need to know the chemical spec on tanks for this standard.

Dionelly de Juan
Quality Control - P.R.

Dionelly, the ASTM standard and the chemical composition of the tank are two different issues.

The ASTM standard specify the thickness of the deposit, and the chromates to be used. And it can be achieved by different bath compositions: zinc chloride or cyanide zinc alkaline, or cyanide free zinc alkaline.

The chemical composition you mention is a cyanide zinc alkaline bath. I wonder if the numbers you provide are in oz/gal or gr/lt. And if the ratio you mention is NaCN/Zn or NaOH/Zn.

The point is that the ASTM standard only specify thickness and chromates to be used, also salt spray hours regardless the chemical composition of the bath.

Guillermo Castorena
- San Luis Potosi, Mexico
2007

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