powdery salt or mineral deposits that form a crust on wall surfaces due to moisture seepage

地下室的墙面出现了大面积的壁癌，白色粉末掉了一地。

persistent mold growth on walls, typically caused by chronic dampness or water leakage

浴室的墙角因为长期潮湿，已经长出了不少黑色的壁癌。