CoatingsPro Magazine

MAR 2018

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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16 MARCH 2018 COATINGSPROMAG.COM Notes From the Blog Editor's Note: Looking for " in the field " information about the latest coating application techniques? We invite you to join the discussion through NACE's new Communities initiative. e following are excerpts from the NACE Corrosion Network 's (NCN) and NACE Coatings Network 's discussion groups for corro- sion professionals with more than 1,000 participants. e following excerpts have been selected for their potential interest to CoatingsPro readers. ey have been edited for clarity and length. Authors are kept anonymous for publication. Please be advised that the items are not peer-reviewed, and opinions and sug gestions are entirely those of the inquirers and respondents. CoatingsPro and NACE do not guarantee the accuracy of the technical solutions discussed. You' ll enjoy a variety of opinions in this practical information exchange forum. To see related discussions from these free list servers, visit volunteer.nace.org/ communities. Erosion-Resistant Lining for Slurry Tanks Q: Does anyone know of a suitable liner for abrasion and corrosion resistance on a very high-solids content slurry composed of fine mineral parti- cles, less than 0.25 mm (0.01 inch) with approximately neutral pH? A rubber lining seems to be the way to go to me, but perhaps someone has experience that says that a spray applied polyure- thane or polyurea could do the job. e substrate is a large steel tank. A: e service history of rubber in abrasive service is hard to beat. at's why tires are made of the same stuff in one of the most abrasive services I might consider. I would add in more detailed definition from soft natural rubber and would add 0.64-cm (0.025 inch) thickness minimum for severe abrasive service along with a double layer at the most abrasive locations. If the water contains even trace amounts of organic chemical compounds, other choices may provide optimum performance, such as a semi-hard rubber or maybe a plasti- cized urethane or polyurea. Keep in mind that the plasticizers often mimic rubber in resistance to the organics that attack rubber. If this latter is a concern, I would recommend acceler- ated chemical resistance immersion tests with cold wall (Atlas cell, and raise the temperature a few degrees). en observe conditions before and after, including the Durometer hardness change, substrate appearance after exposure, and micrographs of a coating cross section to aid in a final decision. A: e only other issue to guard against are the seams. Rubber being an organic material, it could be attacked by organics. Small Bore Pipe Coating Q: For a small pipe that is to be internally coated, how do you confirm the surface roughness and salt level in the middle of the pipe length? Is there a standard that addresses these issues? Do we just rely on the measured values we can get at the ends? A: You have to ensure that your blasting process parameters are the same for the full length of each pipe, then you can be reasonably assured that the surface roughness will be consistent. If you're in doubt about salt level, flush the pipe with potable water then dry before blasting. Airless Spray Equipment Q: We need to buy one piece of airless spray equipment. We got a price quotation of airless spray equipment with a motor-operated type, but some are telling us that it is not advisable because of fire hazards. Can we go with that, or should we buy air-operated? A: Many paint products are designed specifically for airless application. For large surfaces, it is much more efficient to attain the required DFT (dry film thickness). I'm not sure about fire hazards, but the pressure at the spray gun is the pressure of the driving air pressure to the pump multiplied by the pump ratio. is can result in pressures that can penetrate the skin, requiring a safety catch on the trigger to prevent accidental release. Check the paint manufacturer's product technical data sheet for recommendations. A: I imagine you are talking about a gas motor airless spray pump. Yes, that equipment is not suitable for high-solvent coatings. It is a lot safer to use an air-driven motor. Since you usually have compressed air at the site, it is easier and safer to use air than gas or electricity. An intrinsically safe electric pump would be three or four times more expensive than an air pump. Polysulfide Sealants Q: We are in the process of speci- fying a 30- to 40-mil (762.0 to 1,016.0 microns) coating system for Coating DFT and Applying Solid Epoxies

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