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How to deliberately accelerate crazing and cracking problems of powder paint



November 24, 2008

Hello,

I would like to simulate the formation of crazing, checking, cracking problem with the powder coated steel surface. I will apply zinc-phosphate primer than polyester powder paint to the surface. Which conditions I have to try in order to get this surface problem. Poor curing?, weathering in extreme conditions too hot or too cold ? Humidity ? or any other conditions that will accelerate the formation of these surface problems.


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Thank you very much.

Kenan Aybasti
powder paint application - Turkey



November 28, 2008

At first glance it appears that the cause of the of the defect is the primer and the powder has followed its wrinkled profile. You do not state what the resin system is, only that it is a zinc/phosphate primer. Is it a resin/solvent type that depends upon its cure by air-drying? If you are environmentally conscious, then zinc containing primers are a no, no. The zinc will affect plant and marine life. It also affects animal/humans by attacking their internal organs. Try Anoprime which is both an environmentally and animal friendly primer, specifically formulated for PC.

Terry Hickling
Birmingham, United Kingdom



December 2, 2008

I have to dispute a statement Terry made. (We usually agree).

"The zinc will affect plant and marine life. It also affects animal/humans by attacking their internal organs. "

Anything will affect plant and marine life, but the implication here is that it will adversely affect them. In fact theres a huge volume of research on this, and adverse affect is minimal to zero. Zinc has been classified by the EU risk assessments on compounds as not harmful.
To say that it attacks animal/human internal organs is grossly misleading. Its like saying Oxygen is poisonous. It is, but only in certain concentrations, and without some of it we die.
So with zinc, it is an essential element for life, and without it you get very sick.
Its true that a gross overdose of zinc in some forms can harm a person, just like water, oxygen etc can harm.

The use of zinc as a corrosion protection system has not been shown scientifically by any reputable body to be harmful.

geoff_crowley
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
crithwood logo



December 2, 2008

My apologies to Geoff and other readers - after I read the original posting I then rightly or wrongly assumed that the zinc- phosphate primer mentioned was what we call etch primer and our American friends call wash primers. These were used for many years by powder coaters as a low cost, but effective alternative to chemical phosphating. The main anti corrosive ingredients are, zinc chromate or zinc tetraoxichromate (two pack) or a 50% substitution of the chromate portion using zinc phosphate (one pack etch for dip tanks). My mistake in my posting was that I missed the word 'chromate'. Therefore, all zinc references should have read 'zinc chromate'. Many years ago coating mf were asked to find suitable alternatives but these primers are still being manufactured using ZC/ZTC, however, the labeling now requires hazard warnings. Sorry for the misunderstanding and thanks to Geoff for quite rightly pointing this out.

Terry Hickling
Birmingham, United Kingdom



December 5, 2008

Now Zinc Chromate as with most Cr containing things is indeed a problem.
Thanks for clarifying Terry.

geoff_crowley
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
crithwood logo


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