Analysis of organic-coated steels by using small-angle neutron scattering

Small angle neutron scattering (SANS) was applied to analyze the degradation of an organic coating layer on steel and for the non-destructive evaluation of the corrosion behavior of the coated steels. The steel was a modified AISI 1004 steel with 1.2% aluminum and 0.8% chromium to improve corrosion resistance. The organic coating layer was epoxy primer, which was painted with about 250-mu m thickness on the steel. The organic-coated specimen was subjected to wet-and-dry cyclic corrosion conditions for 112 days in artificial sea water at 40A degrees C. The corrosion potential and the corrosion rate of the steel were -1.1 V-SHE and 8.8 x 10(-5) A/cm(2), respectively. SANS spectra showed that nano-sized defects were not formed in the organic layers after the 112-day wet-and-dry corrosion test. Artificial cracks of the organic layer by X-cutting made corrosion spots of submicron size after a 2-day wet-and-dry corrosion test, which were monitored by SANS.