Water Immersion Testing ASTM D870

Ron Rompen

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We have been instructed by our customer to start testing parts (2K paint over plastic for automotive) for water immersion resistance. The standard is TSH1505G (Toyota) which is derived from ASTM D870.

The test standard is pretty basic, and I understand what is required. However, what I am unable to get clarification on is how long to let the part age before conducting the testing. We cure the parts at 180? F for 30 minutes (paint supplier recommendation) but this is not a 'full cure', and the topcoat will continue to outgas and convert for some time.

Does anyone have any experience with this test standard, or with something similar, that can provide guidelines that I can show to my customer to validate my rationale for not going direct from the line to immersion testing?
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