Paint is Fading Looking for Test
Paint is Fading Looking for Test
(OP)
I have been asked to investigate a problem that involves fading of paint when exposed to sunlight for longer than 3 weeks. The surface material is Aluminum. The paint color is black. The product comes in already painted, and we affix it to another part. But after 3 weeks the painted surfaces changes from Black to Grey. We suppect that the UV additive was not used, but we can't figure out how to tell with a simple quick test. We have a UV chamber, but this test is 500 hours or 20 days. Any IDEAS on how to test a painted surface for UV protection quickly.
I thought I would use the most powerful tool in the universe, ENG-TIPS.com to find a conclusion to this conundrum.
Best,
Cervantis
I thought I would use the most powerful tool in the universe, ENG-TIPS.com to find a conclusion to this conundrum.
Best,
Cervantis





RE: Paint is Fading Looking for Test
RE: Paint is Fading Looking for Test
If you have the UV Fadeometer there are accelerated tests that you can use.
http://www.glossmeters.com/
http://acceleratedclimate.com/equipement.htm
Is the paint chalking or just turning gray.
RE: Paint is Fading Looking for Test
Thanks,
JOHN
RE: Paint is Fading Looking for Test
Presume that exposure is to sunlight if UV is causing the fading. What type of coating is your supplier using? If you have the ability to specify the coating it could solve the problem.
Yosh
RE: Paint is Fading Looking for Test
RE: Paint is Fading Looking for Test
RE: Paint is Fading Looking for Test
Confirm with the paint/coating manufacturer than an inorganic black is being specified.
Also, if your aggregate material is Al, make sure that a zinc binder or cobalt drier ingredient in the coating is not galvantically acting to create the oxidization.
RE: Paint is Fading Looking for Test
Best,
Cervantis
RE: Paint is Fading Looking for Test
RE: Paint is Fading Looking for Test
I have used it exposed to high intensity arc lamps illumination at a few solar constants for over 10,000 hours with "no change".
I suggest you look at this type of source for the paint.
RE: Paint is Fading Looking for Test
I don't know your end use, but powder coatings (PE) show very good resistance to natural sunlight. I am referring to architectural grades.
For future reference, you may check the 'fingerprint' of the material using FTIR analysis methods, however, i'm not sure how good this would be for an anodised finish.
RE: Paint is Fading Looking for Test
RE: Paint is Fading Looking for Test
Have you ever heard of 'Qualicoat'? This is an accepted standard in Europe & M.E. for architectural specifications. Some of the biggest manufacturers of PC are members, i.e. Jotun Powder Coatings UK/Thai/Dubai, Akzo Nobel Powder Coatings UK/Turkey/Egypt/Dubai, Sonneborn & Rieck etc.
Maybe it's worth looking at their spec for their benchmarks on anodising (chrome free) and powder coatings.
The latest spec is edition 12.
RE: Paint is Fading Looking for Test
I am familar with AKZO NOBEL POWDER COATINGS. We should be getting in the new product soon, and I will give all an update on our findings. The preliminary testing was very favorable for this "new" style we are going to. I have moved on to other issues/head aches like inconsistencies in DYE pressed parts. I am sure there will be a post sometime in the future on this "diddy". Thanks to all again for your time shared on this concern and for all the great information.
Cervantis
RE: Paint is Fading Looking for Test
I have used "black stove paint" for the interior and exterior walls of our solar simulators that use 4200 Watt xenon lamps, a type used in theater projections systems. The walls are about 15 to 20 inches from the lamp and show minimal discoloration after 15 years of operation of 50 hours per week.
The choice was somewhat accidental but was selected for high temperature stability- based on home use on a wood stove.
RE: Paint is Fading Looking for Test
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RE: Paint is Fading Looking for Test
I suppose the end use and type of paint used is feasible. Did you calculate the CIELAB or are you making a visual comparison? What was the gloss retention of the coating like? Apologies for being so dismissive, I have a tendancy to focus on the abilities of powder coatings only, as per experience.
RE: Paint is Fading Looking for Test
-visual estimate, reflectivity went from about 10% to perhaps 40% over the full time period.(>80,000 sun hours).
-this is a very extreme exposure.
- using Z306 or L300 could be considered but probably out of the question by cost reasons. Stuff is for thermal control of spacecraft.
RE: Paint is Fading Looking for Test
Our new upgraded material is now in house. We begin our QUV testing today. I will have results on this new lot in 22 days and let the group know where we stand.
PS..I have a new post in Polymer Eng if anyone wishes to chime in.
Thank you again to all for your kindness, interest, and willingness to share the vast wealth of collected combined knowledge.
Cervantis
RE: Paint is Fading Looking for Test
As the base color is black, the most likely pigment is going to be carbon black. In general, carbon black is very UV stable and is used as a UV stabilizer.
What you are describing seems more like chalking, which is typically a breakdown of the resin, which turns light colored and powdery.
There are ASTM tests to measure chalking.