In the early days, many application scenarios in China required bolts with high corrosion resistance. Electrogalvanized bolts often failed to meet design standards; while hot-dip galvanizing had certain corrosion resistance, its thick coating (due to process characteristics) tended to damage thread precision, leading to difficulties in nut matching. Dacromet treatment perfectly filled this gap: its corrosion resistance is about 10 times that of ordinary galvanizing, and the treatment process does not damage threads, allowing normal matching with conventional nuts. It also has no hydrogen embrittlement risk and can withstand a certain high temperature (usually suitable for working environments below 300°C). Therefore, most bolts used in automobiles, motorcycles and other means of transportation currently adopt Dacromet treatment.

The Dacromet process was developed in Europe in the mid-20th century. At that time, some European regions had cold and humid climates, and chloride ions in the air (such as salt spray) easily corroded metal substrates quickly, causing severe damage to transportation tools. Scientists thus developed a water-based coating containing zinc powder, aluminum powder and chromate as core components. After applying this coating to the metal surface, it forms a closed zinc-aluminum-chromium composite anti-corrosion layer through high-temperature baking and curing. In the following years, this process was incorporated into the procurement system of the U.S. military and has been used as a national defense-level anti-corrosion technology to this day. After years of development, Dacromet has been fully civilianized and is widely used in multiple fields such as electric power, construction, automobiles, and engineering machinery.

The treatment process of Dacromet bolts is completely different from cold galvanizing (electrogalvanizing). Its core process is coating-baking curing rather than electrolytic deposition: first, thoroughly clean and dry oil stains and oxide scale on the bolt surface; then uniformly apply Dacromet coating (containing zinc powder, aluminum powder, binder, etc.) to the bolt surface (by dipping, spraying, or other methods); next, send the coated bolts into an oven at 180-250°C for baking for 20-40 minutes, allowing chemical reactions between components in the coating to form a dense composite anti-corrosion layer. After the process is completed, the bolts do not require additional polishing, brightening, passivation or other treatments, nor do they need a hydrogen relief process. Additionally, the coating does not contain heavy metal pollution (conventional Dacromet contains chromate, and chrome-free environmentally friendly Dacromet is now available), making it one of the mainstream surface treatment methods for export bolts.

Dacromet bolts have prominent advantages: compared with electrogalvanized bolts, they not only have significantly improved corrosion resistance but also a more uniform coating thickness (usually 5-15 microns) and strong adhesion. Even if slight friction occurs during logistics transportation or installation, the coating is not easy to peel off to expose the substrate, avoiding the formation of open corrosion points. Compared with hot-dip galvanizing, Dacromet coating is thin and uniform. When treating nuts, it will not cause internal threads to be filled due to excessive coating thickness, ensuring normal screwing and installation between nuts and bolts without the need for subsequent tapping correction.