Yes, it can! Although the oil coated on the pan makes a huge difference with the initial use, a carbon steel pan can definitely still rust with time—turning much browner than it was before and being not as effective as it was initially. Washing the carbon steel pan with regular dish soap can inhibit rust—water and other fluids will cause a reaction in iron and the drinking water will actually become contaminated. So, in other words—stay away from regular dish soap, water, and liquids!