Common high-activity activators are mineral acids, often together with halides, amines, water or alcohols:
* hydrochloric acid, most common
* phosphoric acid, less common, use limited by its polymerization at higher temperatures
Inorganic acids are highly corrosive to metals even at room temperature, which causes issues during storage, handling and applications. As soldering involves high temperatures, compounds that decompose or react, with acids as products, are frequently used:
* zinc chloride, which at high temperatures reacts with moisture, forming oxychloride and hydrochloric acid
* ammonium chloride, thermally decomposing to ammonia and hydrochloric acid
* amine hydrochlorides, decomposing to the amine and hydrochloric acid