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CL BLOG Continued from page 51 where base metal is severely corroded. As a technology for the thicknesses and the temperatures described, it would be less sensitive than ultrasonic means for thick- ness measurements. A It is unlikely that thermography would be of any real help other than to identify hot spots where the lining has already failed and There are a number of in situ devices that might be used to test the integrity of critical areas of your lining as an online indication; these would only have mean- ing if supported by regular inspection. A Thermography depends on tem- perature differences to visualize differences in coatings or other substrates such as concrete, over- laid decks, etc. If the system is isothermal, or close to it, very little will be visible. If the system is being heated—for example, ÅTTML _Q\P PW\ TQY]QL¸LMTIUQVI\QWV QV the coating system should be visible on the outside if you can gain visual access. The "resolution" of the system will likely be two or three times the thickness of the substrate. It depends on the thermal conductivity of the substrate and the amount that the thermal conductivity is UWLQÅML Ja \PM LMTIUQVI\QWV AW] _WV¼\ see small delamination very well. Looking from the inside, it would be VMKM[[IZa \W KZMI\M I PMI\ ÆW_ \PI\ KW]TL JM IZ\QÅKQIT WZ [WUM\PQVO I[ KWUUWV as sun, shade, or sprinkling with water. Tank thickness/lining thickness can be JM\\MZ R]LOML ][QVO ]T\ZI[WVQK \MKPVQY]M[ some of which may pick up delamination. The downside to this is that the readings are spot readings, which means taking a large number of them. We did some brief experimentation with a thermal imaging camera for a similar application. We wanted to track the ongoing deterioration of the ce- ment mortar lining on a large-diameter aboveground pipeline. Discrete areas of the lining were known to have delami- nated from the pipe wall and we wanted to devise a way to monitor this deteriora- \QWV 7]Z Y]M[\QWV _I[ ¹,QL \PQ[ WKK]Z immediately after installation or was it an ongoing deterioration?" If it was an ongoing process, we wanted to learn the rate of deterioration in order to plan and budget for the eventual (and expensive) relining of the pipeline. We had noticed that on rare occasions, the pipe would sweat in a pattern that ex- actly corresponded to the shape of the de- lamination beneath the steel. This ghostly phenomenon was apparently due to air and steel temperature, humidity, and dew point. Our thinking was that there must be a way to visualize these temperature zones to track the advancement of the lining delaminations. The lining would fail in large sheets that theoretically could be "seen" from the outside. The thermal imaging did not work— VW\ JMKI][M \PMZM _MZMV¼\ \MUXMZI\]ZM 52 MATERIALS PERFORMANCE November 2012 NACE International, Vol. 51, No. 11