Materials Performance

DEC 2014

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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46 DECEMBER 2014 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 53, NO. 12 Continued from The MP Blog, p. 13. The following items relate to coatings & linings. Please be advised that the items are not peer-reviewed, and opinions and suggestions are entirely those of the inquirers and respondents. NACE International does not guarantee the accuracy of the technical solutions discussed. MP welcomes additional responses to these items. They may be edited for clarity. Protecting machinery foundation Q: We have a machinery foundation made from carbon steel (CS). The foundation is designed to be normally dry, but it might be in contact with salt water or oil at times. Once the machinery is mounted, it will be physically impossible to repair any corroded areas of this foun- dation short of dismantling the machin- ery, which is quite unpractical after installation. We are looking for more or less permanent protection (30 to 50 years). Some of us are considering stainless steel (SS) explosive cladding. Does anyone have any other suggestions for the clad metal and the method, other than explosion cladding? If we use SS, what grade should we consider? The foundation is not yet constructed. A lso, the base is CS. We do a signif icant amount of thermal spraying and are very familiar with the process; however, it may not be adequate for this particular appli- cation. The limited thickness and poros- ity of thermal spray metals may be a problem for this job. The machine is made of CS and is located on a ship. A: I would suggest metalizing with a seal coat of poly urethane (PUR) or poly urea. Te PUR seal will protect the metal from the salt water and oil. If the machine remains indoors and is usually dry, this method should easily qualif y for the 30 years of minimum protection. Make certain that the base is pitched downward from the geographic center to all of the edges so that condensation will run of and away from the steel. Be sure that maintenance of the drainage is built into the foundation and base. A: You will need to consider that if you use SS, the foundation will now be cathodic to the machine so any small defect areas in the machinery coating will be the anode and you'll now see high corrosion rates on the machine rather than the foundation. You could put a high-performance coating on the SS foundation but I think the thermal spray and sealer approach is your best bet. I've seen accelerated corrosion on both machine bases and CS foundations where base stainless shims have been used. If you have the entire foundation in SS, I think you will have real problems keeping a coating on the machinery. BLOG

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