The GILDES computer model has been used to simulate the exposure of copper at room temperature to ammonium sulfate particles at 93% relative humidity. The dominant corrosion products formed are cuprite and the basic copper sulfate antlerite. The amount of antlerite depends only on the original amount of ammonium sulfate. The effect of drying has been included in the model for the first time; it influences the amount of cuprite formed, as does the presence of metastable corrosion products. Variations in pH during the calculations can be attributed to specific events corresponding to starting or ending points for the dissolution or precipitation of corrosion products.