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pfonline.com/experts 32 JUNE 2014 — pfonline.com PAINTING C L I N I C William H. GouGHenour Jr. Consultant paintingclinic@pfonline.com Cure Time for aluminum Conversion Coating Q. How long should I allow an aluminum conversion coating to cure prior to applying an epoxy primer and polyure- thane topcoat?—T.W. A. The short answer is to correctly follow the prototypical steps in the specific coating's preparation process. Your coating supplier or representative should be able to provide a technical data sheet with the exact specifics and parameters. Testing Standards for Coatings Q. We manufacture a wide range of metal and wood furni- ture. Can you help us identify any types of coatings performance testing that we should be conducting to insure we are meeting industry quality standards?—D.H. A. Product performance and liability are major issues for manufacturers today. Adopting proper coating perfor- mance testing using standards such as ASTM (American Society for Testing & Materials) will help to insure you are meeting the performance and quality challenges related to industrial coatings issues. There is a wide range of standards for finish performance, and consumers over the years have helped form what these should be. There are several things to consider as you set out to do ASTM testing. Testing equipment can in some cases be rather expensive and may require proper training to operate correctly. You may want to weigh purchasing equipment and conducting the testing internally verses sending it to an outside laboratory for evaluation. You may also find that your coating supplier can provide some of these services for you as well. If you belong to a particular manufacturing association, it may be able to guide you to a set of industry-related standards. I have compiled a short list of a few common ASTM standards that may be of help to you in evaluating what you may want to test for: • ASTM D1308 Chemical Resistance is a visual test to determine the affects of various household chemicals. • ASTM D3359 Cross Hatch is a common test that determines how well a coating will adhere to the surface after the coating has been scratched and pulled off with tape. • ASTM D3363 Pencil Hardness will determine how hard the coating surface is. • ASTM 4060 Abrasion Resistance will determine how well the surface holds up to abrasion, simulating a lifetime of service. • ASTM D 2794 Impact Resistance will determine how well a finish will adhere and hold up to a sudden impact. • ASTM D 2091 Print Resistance of Lacquers will help determine how well a finish will hold up when heavy items are placed on it for extended periods of time. Will it leave an imprint once the item has been removed? • ASTM D 523 Specular Gloss will help ensure you are shipping the same sheen level with every order. Pardon the pun, but I have not even begun to scratch the surface as to the myriad of ASTM physical property tests that can be conducted on coated surfaces. There are tests for the affects of boiling water, hot/cold cycles, UV exposure, color variance—on and on you can go. If you do not already have a quality assur- ance department, I would recommend that your organi- zation form one. Then, this internal department can identify what ASTM testing to adopt and build into manufacturing quality performance standards. This will help ensure that your customer is getting consistently manufactured products. Once you have adopted the ASTM standards for coating performance and implemented them into the quality standard, the next challenge will be to estab- lish accountability from the supplier all the way to your employees. Typically, once everyone sees the benefits of testing and quality policies, you will begin to see favor- able results. Paint Delamination issues Q. We manufacture molding for the RV industry using specialty laminated wood from China that has been extruded with "gesso" that we then coat with water-based paints. Next, we wrap the molding with various papers and veneers using PUR (polyurethane reactive) glue on a glue machine line. Lately, we have been experiencing some delamination of these materials down to the gesso layer. As we looked closer, at we noticed that the paint we are using is sticking to the PUR glue bond on the backside of the delaminated veneer/papers. In your experience, do you know what could be the issue?—B.L. A. This is not as uncommon a problem as you would think. First, you need to understand what "gesso" is. Gesso, by definition, means chalk, and it has been used for hundreds of years to size or level wood and metal for processes such as paint, gold leaf, etc. Many of today's gessos are made with materials ranging from calcium carbonate (CaCO 3 ) to kaolinite (Al 2 Si 2 O 5 (OH) 4 ). These powdered materials are typically mixed with aqueous or oil bases, then applied with an extrusion die machine process and allowed to thoroughly air-dry. 0614_PF_PaintingClinic.indd 32 5/16/2014 1:40:33 PM