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Salt spray life of lead plating?





June 20, 2012

Q. Dear sir

We are India's leading manufacture of fasteners.

We are doing lead plating on nuts and bolts, as demanded by our customers.

Can you tell me salt spray life of lead coatings?

Waiting for your early reply.

Thanks

Ravitesh Singh Kaloti
- India



First of two simultaneous responses -- June 21, 2012

A. That would depend on how thick the coating is. There is a high probability that the valleys in the threads will not plate very thick and or not at all, I would expect salt spray testing to have a few early failures.

James Watts
- Navarre, Florida



Second of two simultaneous responses -- June 22, 2012

A. Hi Ravitesh,

So many things can affect salt spray life, you are going to have to give us more details about your process.

How thick is the lead coating? This is probably the main factor in determining how long a part will survive a salt spray test.

Do you use any post treatments, such as clear coats or proprietary dips to improve corrosion resistance?

Are the parts plated all over or is there a possibility of bare areas, where the plating would not be protecting the base material.

And finally, what are you trying to show with the salt spray test? This test does not reflect in-service life and may lead to you making conclusions about the coating that are not valid for real time situations.

Brian Terry
Aerospace - Yeovil, Somerset, UK



July 9, 2012

Q. James Watts: Sir, thickness of the lead plating is from 20 to 25 micron. I have not done salt spray life test but I have tested my samples in Sulfuric acid (40-50% diluted) for 5 days; the result was ok as there was no sign of white and red rust.

Brian Terry: Sir, thickness is : 20-25 micron.

I am not doing any clear coats or proprietary dip in the process. As I think lead is a component that has high resistance to corrosion, so there is no need to do coats & dip. Please suggest, if you have any coats or dips as I want the best.

Yes, in fasteners the valleys in the threads are not catching proper plating. It is taking a long time to coat the inner thread valleys of nuts & bolts. Please give a solution?

I just want salt spray life test to compare between stainless steel fasteners and the lead coated fasteners.This is my main purpose. Which one is best as lead coating costs 1/2 price of stainless fasteners.

Ravitesh Singh
- India



July 12, 2012

A. Hi Ravitesh,

The thing is that it doesn't really matter what a predicted life of lead plating for a given plating is given that you are going to be doing direct comparisons to stainless steel.

I would be careful, as James noted you will get less coverage in the root of the threads and this will be a potential failure point.

I think that what you need to do is design an experiment, taking the thickest and thinnest expected plating and running the samples with stainless steel in salt spray. Keep an eye on the plated and unplated parts and look for red corrosion product (indication of base material corrosion). Your conclusions will be quite simple, either the lead plating will give you equivalent corrosion protection or it will not.

Brian Terry
Aerospace - Yeovil, Somerset, UK



July 13, 2012

A. Sir,

I will surely do the experiment in salt spray. To test whether the lead plating will give you equivalent corrosion protection to stainless steel or not.

As in this website there is no theory on the lead plating. So let me test and report you within 2-4 days.

Sir, please help me in finding proper post treatments, such as clear coats or proprietary dips to improve corrosion resistance after lead coating has been done.

thanks,

Ravitesh Singh
- India


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