Selective oxidation and reactive wetting of a 1.0% al-0.5% Si TRIP-assisted steel

The selective oxidation and reactive wetting behavior during hot-dip galvanizing of a 1.0% Al-0.5% Si TRIP-assisted steel was studied. The effect of process atmosphere oxygen partial pressure on selective oxidation was investigated with a focus on surface chemistry and oxide morphology. The oxide chemistry and morphology were then related to the reactive wetting behavior. Two process atmospheres will be discussed: a -53°C dew point (dp) with a N 2 - 20% H2 atmosphere and a +5°C dp with a N 2 - 5% H2 atmosphere. The -53°C dp resulted in good reactive wetting whereas there were an increased number of bare spots in the galvanized coating for the +5°C dp. The reactive wetting results will be discussed in the context of the effect of process atmosphere on the steel surface chemistry and microstrucrure.