We use an iron phosphate pretreatment, and I need some help in finding an independent group that does coating weight samples on 4 × 12-inch flat panels. B.T.
I am not aware of any laboratories that specifically perform coating weight analysis on panels or product, although I would think that they must be out there. They likely do not necessarily advertise this as a specialty since this would not be a high volume business.
I would suggest you contact a local laboratory that you may currently work with for wastewater or other testing you may have done. Although I can't quote you a specific standard, the method I am familiar with involves weighing the test panel, immersing it into a hot chromic acid solution (about 20% by weight) for one to two minutes, rinsing, drying and re-weighing. This should be repeated until a constant weight is achieved (i.e., at least two consecutive final weights are the same which indicates all the coating has been removed). Since this method does involve chromic acid, it is advisable to have trained laboratory personnel working with proper ventilation perform this test.