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Conforming to 300 hours salt spray test for sheet metal items


Q. We manufacture Fuel Tanks of 165 Ltrs to 350 Ltrs capacity for Commercial Vehicles. We wish to make our Products conform to 300 Hour Salt Spray test conditions. The material used is CR steel sheets of 1.6 mm thickness.

1.What is the finishing process that we need to implement that would ensure conformation to 300 hours salt spray test?
2. Our products being bulky, is the 7 tank process feasible?
3. Are there alternatives to the 7 tank process?

Suresh Narayan
Sheet Metal Fabrication - Chennai, TamilNadu, India


? Hi Suresh,

You need to provide more information. Are these tanks painted or unpainted? That makes a big difference.

George Gorecki
- Naperville, Illinois


A. Suresh

If you wish to plate zinc both inside and outside the fuel tanks and then chromate the zinc I would suggest looking at the Zinc Iron alloy, provided your specs permit Zinc Iron Plating.

Zinc iron alloy lasts in excess of 300 hours to white rust and can be plated inside hollow preformed and welded shut articles having small openings.

Zinc Iron is certainly better than Zinc Phosphate for corrosion resistance.

Zinc Iron alloy accepts paint too. The materials are locally available and a plating plant can be sourced domestically for this job.


Asif Nurie [deceased]
- New Delhi, India
With deep regret we sadly advise that Asif passed away on Jan 24, 2016

July 24, 2008

Q. Spec ZnPh r10f - Phosphating to be done on the casting and it should confirm to 300 HSS/RR.

Is it possible to achieve this spec. Please advise.

sankaran saravanan
- - Chennai, India

Hi Sankaran. I don't know what "ZnPh r10f" means. George previously noted that you must clarify whether you are painting this item, or what. Most paints or powder coatings on zinc phosphate will pass a 300 hour salt spray test. But bare zinc phosphate is not intended as a finish and you would be lucky to reach 300 hours to red rust if the parts were just sitting on an inspection desk :-)


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