The pros and cons of powder coating

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alumioforte
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Joined: Sun Nov 27, 2016 8:08 pm

The pros and cons of powder coating

Post by alumioforte » Tue Dec 20, 2016 1:04 am

This is a helpful article i thought I would share, being that this is a highly discussed and often controversial topic...

https://www.linkedin.com/pulse/cons-pow ... le-publish

kmorin
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Re: The pros and cons of powder coating

Post by kmorin » Tue Dec 20, 2016 4:55 pm

alumioforte,
not much new in the article that hasn't been on the web for plural years in terms of hard facts and written by a vendor instead of comparison by service vendors- well it translates to an ad more than 'news' of some new development.

As noted the prep is almost assured to need sand blasting to develop any decent anchor pattern for a good bond- and zinc containing chemical bonding agencyare not really compatible due to their performance in the higher temp.s required by the oven melt-the-coating process.

What I think will be needed to make real headway in the market is some test panels using a Brinell or Rockwell hardness type of plunger and impact test of the bond to metals. By this I'm referring to the different 'points' used in hardness testing to dent the parent metal- but I'm suggesting that in the case of aluminum coatings... the tests be used in a slightly different way.

If a sharp center punch is used to dimple steel, and a specific round ball point is used to dent softer metals (hardness testing measures the diameter of the dimples made with a fixed impact energy) - What I'm suggesting is needed; is to use some already accepted aluminum hardness testing spherical point- to make a known force dent in 5052, 5086 and 6061 (as a suggest set of boat building alloys). Only in this case I'm suggesting the powder coating & paints should already be installed on the test panel to whatever spec. is 'standard' and with whatever anchor pattern is' standard' ?

Now the reason for these tests comparing powder coating to marine paint systems: The surface film, powder coat vs paint, is only as hard or durable as the underlying metal. So if a dock, or a rock, or a Glock impacts the hull material - how will the two films powder vs paint- STICK?

My reasoning is that as the impact dents/deforms/displaces the aluminum under the film(s)- their relative adhesion is the real test of useful coatings. It doesn't matter if the films are harder or softer than one another- the issue will be solely that film's adhesion to the metal's surface so there is not 'gap' or lifting of the film. It is under a lifted surface film that corrosion happens- and it therefore critical path to the boat owning public's understanding of the benefits of one film type over another that must be tested by impact tests vs adhesion.

I've mainly been involved with commercial welded aluminum boats, and only painted a few of my other projects; and they were small enough to fit in the ovens implied by your article and ad. But if I were to try to evaluate the paint vs powder coated films for 'value' - I'd want to spend the time to at least create a few test panels and hit them with a ball bean hammer to see which film system adhered to the underlying metal the best?

My view is that without this critical set of testing, without a 'hammer panel' for a potential client to come to a coaters' business and whack some dents? The assertion that this coating system adheres to aluminum "better than paint" will be doubted and growth could could remain very slow? I think President Ronald Reagan is credited with the quote "Trust, but Verify" ?

Just sharing what I'd want to know if I had an oven large enough to hold even a small skiff in my area. Adhesion in deflection NOT hardness/durability of the film seems most critical with an underlying soft metal? Hope I've been able to make the question neutral to explore, I have "no dog in the hunt" for the 'best' protective/decorative film for aluminum- the Miracle Metal is fine all by itself for me - but adding colors and designs is nice for many boats.

Cheers,
Kevin Morin
Kenai, AK
kmorin

kmorin
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Re: The pros and cons of powder coating

Post by kmorin » Wed Dec 21, 2016 2:20 pm

alumioforte,
talking about this question - adhesion of coatings to aluminum in general use and specifically in impact areas- I was reminded that another good test would be to have a panel of each alloy coated for comparisons and bend those panels.

That test, of bending in a leaf fold type brake and in a press brake, would not have to be a full 90 deg bend to make the test valid to compare the two groups of coating films' performances. Just a 10 deg or 15 deg test would simulate what a rock impact, dock impact, too-hard bounce on the trailer or any other rough treatment of the coating that might result in separation from the metal.

Anyway, just another builder's opinion of how you might test adhesion in the 'worst case' of dents, dings and damage locations on a welded aluminum boat.

Cheers, and Merry Christmas

Kevin Morin
Kenai, AK
kmorin

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