Brief answers using bullet points

Briefly explain how the balance between the rate of production of metal ions within a pit and the rate that they can diffuse out of the pipit affects whether a pit will continue to grow or repassiveate ("die") 2 Marks (b) An architect worked with a stainless steel company to develop decorative patterns on the surface of stainless steel sheet by abrading the surface with hard steel brushes to make directional patterns. However, when the sheet was put on the outside of the building, which was near the sea, obvious rust spots developed in the abraded patterns but not on the smooth parts of the steel sheet. In addition, when cleaning cloths were used to attempt to remove the rust stains, they would catch on the abraded regions and tear. They found that using a hard plastic scouring pad on the surfaces gave a smoother finish that retained the directional patterns and was more corrosion resistant. Briefly explain why the pattern produced by the steel brush led to pitting corrosion, while patterned regions treated with the plastic scouring pad and the original smooth surfaces did not show signs of pitting. 3 marks