Specification for powder coating so we can give 5 year Warranty

A. So then, this would make you the first person in the history of NY that has had a project like this? :-)
If this has never been done successfully, where are you going to find the magic dust that will give you the edge? If it has been done successfully, research the process and duplicate it.
The primer for powder coating is a properly pretreated substrate, if the powder coating on the product that you have now is flaking, the substrate was not pretreated properly (is it failing before it even gets installed?) or the paint is undercured.

A. Hi, Brian. Putting zinc on a steel item sacrificially protects it so it will not rust in a scratched area and will last longer. A zinc based primer is one way to do it, but is still easily scratched through to the steel, and not the equal of zinc plating under the paint, which is not the equal of hot-dip galvanizing under the paint -- primarily because of the weight/thickness of the zinc.

Regards,

A. Hi Paul. Warranties are a difficult situation. Get your powder coater to supply a non-revokable surety bond to pay the warranty costs if something goes wrong.

But I don't think the spec is adequate. I think you need e-coating after the phosphate. I'm not sure you need the zinc-rich primer. My e-coated & powder coated expanded metal patio set (see letter 34112 for photo) has lasted 13 years on a salt water lagoon with insignificant rusting (probably none at all for 8 or 9 years) and zero maintenance. [Update July 2020: that patio set sat in Superstorm Sandy flood waters for a week and is still in pretty good shape although over 20 years old. Zinc phosphatizing, e-coating, and powder coating can be fabulous]

Opinion! Although specs are important, I personally don't believe you can simply spec your way to quality. It wasn't a simple spec change that let my new Maytag dishwasher fail in a half-dozen different ways within 2 years after my old Maytag washing machine lasted 38 years without a single repair call; it was the company abandoning a former passion. I'm a dinosaur who thinks you can't get quality without taking it personally; I hope you're able to do that from thousands of miles away :-)

Regards,

A. We would not give a warranty on that coating spec. Powdercoating, like paints, is porous, so water will eventually get to the steel.
If it were galvanized first, then a single top coat of powder, it would be warrantable.

By the way, 2.5 wall thickness tubing would more normally be cold rolled, not hot. If it really is hot rolled, what do they do to remove mill scale? Or is the powder adhered to the mill scale, which itself has poor adhesion to the steel?

A. A vexed question.
As the powder supplier is apparently AKZO NOBEL why do you not specify that the applicator be a "Warranty Approved" applicator and for good measure accredited to ISO 9001.
You could then invoke Akzo warranty when your Chinese products fail.
Alternatively you could seek out a good local manufacturer use gal tube as a base and probably Si-Br consumables for any weldments. After that you could look at a similar spec to that proposed in the knowledge that your supplier is accessible and accountable locally.

I think a lot of us lose sight of the fact that quality is a very saleable product accessory.
Perhaps we also lose sight of the multiplier effect on our own economies?
Let us face it if the Steel is local then local people were paid to make it.
They bought local food & local real estate.
The local food suppliers also invested in the local economy and so it goes on.
In Australia we estimate that multiplier effect for manufacturing jobs at ~ 4:1.
Europe does not appear from OZ to be in really good shape economically?
Why not sell quality & patriotism rather than cheap dubious goods?
Regards,
Bill

A. Bill said...
"...You could then invoke Akzo warranty when your Chinese products fail...."

In the U.K. the Akzo Nobel warranty is only afforded to the applicator.
We are an "Akzo approved applicator" and the system here is that the powder manufacturers warranty is to the applicator, and only covers certain aspects (such as gloss and colour fading, resin breakdown etc - the powder itself), whereas the applicator is offering the warranty to the end user/ purchaser.

So the purchaser can't claim the coating manufacturers warranty directly.

Good points about local supply. We have a customer in playground equipment and he finds that buying local is a saleable attribute. He advertises that his products are made, coated, assembled within a 30 mile radius, and local authorities who buy see that as a value-added aspect.

A. Good point Geoff.
I suppose I was thinking more along the lines that to gain Warranty Applicator Status you have to be accredited by the Powder Supplier and subject to random check visits.
So, a combination of ISO 9001 (giving assurance of repeatability and record keeping) and warranty applicator status (giving assurance of performance level)would be comforting.
It is OK to perform cure, adhesion, impact resistance, abrasion resistance, salt spray et al once the goods arrive but what do you do if they are found to be defective?
It is a "slow boat to China" and slower returning.
Regards,
Bill