Problem Solving Forum
March 13 - March 19, 2016
On a recent project, complex pre-fabricated, hot-dipped galvanized panels exhibited thicknesses in the range required for the entire subsequent coating system. It was not practical or possible to accurately map the thickness of the galvanizing across all the various parts, and DFT gauges available only measure the entire non-ferrous coating, including the galvanizing. How should thickness-per-coat minimums and maximums be controlled and verified for subsequent coatings?
Robert Kincheloe of NACE Independent QA Inspector on
March 17, 2016:
HDG is applied by weight not thickness. Dipping te ...read more HDG is applied by weight not thickness. Dipping technique is also a variable. In my experience I've seen DFT thicknesses from 2.0 to 18.0 mils per item. Therefore, a DFT base-line test should be performed on galvanized items prior to additional coating applications. Each application should be DFT-tested. Proper wet film thickness testing during coating applications also can help to verify that coating thicknesses are correct.