| To examine the effect of acid fog on corrosion fatigue characteristics in SNCM steel and its weldment, fatigue test under acid fog environment was carried out in comparison with distilled water. The corrosive constituents in acid fog piled up the corrosion products on crack face and caused a crack branching and crack tip blunting. Therefore, crack growth rate under acid fog (pH = 5) was reduced by decrease the effective stress range in crack tip rather than that of distilled water. Also, it wart found that corrosion behavior was remarkably dependent upon not only pH and Hz but also constituents of acid fog. When the fatigue cracks are subjected to strong acidic solution and slow testing speed, the crack face dissolution was promoted and therefore crack closure was disturbed just as the stress decrease. Also, due to the detrimental effect of acid fog, the critical crack initiation stress, σ_i and crack growth rate, da/dN in early stage crack growth in weldment are slower than those in distilled water. Under the distilled water and acid fog environment, the weldment shows marked behavior that the crack growth rate is considerably low in heat affected zone but accelerated rapidly in weld metal region. |
|
