Black boiled bolts will not rust in general, because black boiled treatment will form an oxide film on the surface of bolts, which will increase the anti-rust function. However, if the bolt meets water, a chemical reaction may occur. If salt, acid or other chemicals are dissolved in water, the oxide film may be destroyed, resulting in rust of bolts. At the same time, if it is placed in a humid environment for a long time, water will gradually penetrate into the bolt, leading to corrosion.
The above information is for reference only. For more accurate information, please consult professionals.