Relating Test Results to Exposure Conditions

Ask an Expert From: Products Finishing, ,

Posted on: 11/1/2003

Question: In the August 2003 issue of Product Finishing you answered a question on Salt Spray/QUV results.

Question:

In the August 2003 issue of Product Finishing you answered a question on Salt Spray/QUV results. Your answer was 100% on target. Degradation is both material specific and location specific and if anyone tells you there is a universal acceleration factor they are mistaken.

I would be happy to talk with you on how we suggest companies can better determine an answer to that question. If ever you need assistance please do not hesitate to contact myself or anyone on my staff. It is always a pleasure to help an individual who understands our industry. Thank you. J.Q.

Answer:

Thank you for writing, J. Q. It’s reassuring to know that someone beside my son-in-law reads the Painting Clinic. It’s also reassuring to know that someone agrees with me. And since we agree, it would be pointless to discuss this issue. Instead, I will take you up on your offer and refer future questions regarding testing using your equipment to you folks.

J. Q. is referring to the question asked by M. H. titled Salt Spray/QUV Test Rersults that appeared in the August 2003 Painting Clinic. M. H. wanted to place a warranty on his product and asked the inevitable question “...Is there a cross reference which relates the hours tested for salt spray/ QUV to the years the product can be expected to last in the field?...”

I’m good, but not that good. So I explained to M. H. “...Unfortunately, I have no references that relate hours in salt spray or QUV to actual hours of real time exposure nor do I know how long 2,000 hours of testing relates to how long a coating will last in the field. One reason is the vast difference in exposure conditions from one locale to another. Another reason is the different effects accelerated tests have on different coating systems....During nearly fifty years of testing industrial finishes, I also noticed that failure modes after exposure to accelerated testing did not always agree with those of actual exposures...” I also suggested to M. H. ...”You may want to ask the suppliers of accelerated testing equipment if they have data relating test results to real time exposure. On the other hand, you can make your own judgment of life expectancy of specific finish systems with relation to accelerated tests if you have actual real time exposure data....”

 



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