Assessing Coating Drying/Cure
{"Image DocumentName": "Assessing Coating Drying/Cure", "Image ImageDescription": "Pencil Hardness (ASTM D3363) Solvent Resistance (Solvent Rubs; ASTM D5402) for convertible coatings. Solvent Resistance (Solvent Rubs; ASTM D4752) for ethyl silicate inorganic zinc primers. Impressor Hardness. Barcol Hardness (ASTM D2583) Durometer Hardness (ASTM D2240) Dry Time Testing (ASTM D1640) There are a host of tests that can be conducted to assess the degree of drying or curing of an applied coating. One or more of these tests may be conducted by the quality control inspector to verify the coating has dried or cured adequately prior to application of subsequent coats, or prior to placing the coating or lining system into service. ASTM D3363 describes a test where pencils containing various hardness of lead are used to attempt to either scratch or gouge the film. The coating manufacturer or the specification would have to indicate a minimum pencil hardness value for this test to be meaningful, as there is no standard pencil hardness. There are two solvent resistance tests that can be used to assess the degree of coating cure; one is used on organic convertible coatings and the other is for use on ethyl silicate-type inorganic zinc-rich primers. Both employ the use of a solvent saturated cloth and finger pressure to conduct a series of double rubs. Resistance to the solvent rub is an indication of the degree of cure. Thick film coatings are typically assessed for the degree of cure using impressor or indentor-type instruments. These include the Barcol harness tester and durometer hardness. In both cases, hand pressure is used to push an indentor probe into the coating. The coating\u2019s resistance to this action is displayed on the gage dial in hardness units. Fiberglass reinforced plastic or FRP linings may be assessed for degree of cure using a barcol hardness tester, and a pipe coating may be assessed for durometer hardness prior to backfilling the ditch. Finally, dry time testing may include dry-to-touch, dry-to-handle, dry-through, and dry-to-recoat, which are all described in ASTM D1640.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}