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Best bolt finish

I am trying to specify a new finish for bolts going on our new product line. I have already chosen the grade and size of the bolts, 3/8-16 x 3.5. I am not sure as to what the best method of having the bolts finished is. They will be subject to salt water/salt air, hot, humid climates and hydrogen sulfide gasses. What is my best bet for a durable, cost effective finish?

Thanks,

Chris Yard
mechanical engineer - Watertown, Connecticut, USA
2004

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2004

Mr Yard.

You did not specify how long you expected the finish to last. We assume you have something like 5-7 years in mind....

In order of cost effectiveness here are suggestions

1) Make Stainless Steel bolts ..
2) Mild steel, with 8 Microns Zinc Nickel 12 percent alloy and Blue Chromate with topcoat.
3) Zinc Iron alloy plate 8 microns with a Black finish + topcoat over Mild steel Bolts for 3 years life expectation.

Regards

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

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2004

Hi Chris,

Mr Nurie is being conservative in granting life expectancy of your fasteners albeit in a corrosive environment. Zinc Nickel and Zinc iron should get you three to five times the above, much more in normal conditions.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India