Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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be retained for further examination as time passes or for reference should a problem arise in the customer's usage. Record keeping on tests should be com- pletely detailed in a bound laboratory notebook, signed by witnesses who have read and understood the test procedure and results. These are legal documents that can be of great importance for a variety of reasons (customer complaints, user litigation, patent applications, etc.). Review of such test records can lead to product/process improvements by noting superior/inferior performances and relating them to supplier or process details. For instance, a coating did not yellow as much on aging when one supplier's tri- ethanolamine lauryl sulfate was used compared with any of four others used (a mi- nor but important detail in the formulation). There is substantial argument for standardized testing. Testers and test spec- ifiers should be intimately familiar with ASTM (ISO, DIN, etc.) standards per- tinent to the industry. Indeed, they should be participants in the formulation and monitoring of such standards to ensure that they are meaningful. It does no good to have a standard test within your organization that exists nowhere else in the world. An alkaline salt fog coating test on steel siding may be a barrier to communication to potential suppliers. Designing a unique test sled and speci- fication for coefficient of friction may be entertaining but has little relation to communication with other labs, be they customer or supplier. If it is that im- portant, have it adopted by a standards organization. Assessment of the testing facility's accuracy may require a collaborative test- ing program. Some collaborative programs are done intermittently by profes- sional associations and the ASTM, but there is one source available at all times. Collaborative Testing Services (Herndon, Va.) has a program that uses ASTM tests twice annually as a measure of how your results match up with other testing professionals. BASIC PHILOSOPHY OF TESTING Tests may fall into two classes. The Class 1 tests are the tests run on every batch or sample because they are crucial to performance or processing. These tend to be simple and quick. Examples may be viscosity or total solids content (and pH for aqueous coatings) for the fluid coatings and hardness, gloss or color on the film. These should be performed in replicates for every batch as a precision check. The Class 2 tests are those run only on special occasions, as when a pro- cessing or formulation problem appears. These might include high shear rheology for the fluid or exposure tests for the film. These tend to take more time and cost more for equipment than the Class 1 tests. What is Tested? The material coming in the door may be accepted on faith and applied to a product that is then shipped out; but there are always slip ups somewhere in your supplier's process, in the materials or in your process. To ensure that the prod- uct you send out has the quality you intend, the testing should start on the ma- terials coming in (quality assurance, QA), on the materials in process (quality con- trol,QC), and on the products going out (QA again). Coating-Liquid Tests Coatings generally enter the user facility as fluids. The incoming QA lab should probably do about four liquid characterization tests on a small (about 4-oz or 100- 280

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