Dacromet Plated Bolts and Nuts

Dacromet Plating is in fact a water based, environment freindly process of zinc and aluminum coating in chromate solution with low friction coefficient that facilitates bolts and nuts with the means to resist corrosion against high humidity and high temperature.

Dacromet Plated bolts and nuts dont face hydrogen embrittlement as opposed to hot-deep-galvanized bolts and nuts, since the coating temperature for Dacromet process is substantially lower than hot deep galvanization and is considered the best possible coating method for bolts and nuts. Further more, some standards of bolts such as ASTM A490 and ASTM A354 DB are prohibited to be hot deep galvanized due to the connection failure caused by hydrogen embrittlement.

Dacromat Plating was first patented by Dacral NDS Co. and the name has been driven from this company. the process involves submerging bolts and nuts in a water solution of zinc and aluminum - aluminum with substantially lower percentage - along with Chromate as solvent in 100 degrees Celsius, for zinc and aluminum particles to take position in layers on the surface of the fasteners. After extracting the bolts and nuts from zinc tub, they are usually centrifuged to lose the redundant particles and then are heated by 300 degrees Celsius so that the layers of zinc and aluminum are very well baked on the surface. in order to have a highly resistant layer the entire process is repeated once more to form a firmly thick, low friction coefficient, blurry silver layer on top of the bolts and nuts.

Dacromet Plating Thickness

Dacromet Plating provides a much thinner layer compared to hot deep galvanized plating. each micrometer of Dacromet layer resists 100 hours of salt spray - with high corrosion properties - which is almost 4-5 times higher than each micrometer hot deep galvanized plating. Dacromet plating is usually done in three different grades as follow

• Grade A 5-7 Micrometer 24 grams coating per square meter
• Grade B 8-10 Micrometer 36 grams coating per square meter
• Grade C 10-12 Micrometer 42 grams coating per square meter

Bolts and nuts and fasteners in general are usually manufactured having Grabe B of Dacromet coating resistant to 800-1000 hours salt spray. following is the salt spray test on three differently coated bolts and nuts for 360 hours. as you can see hot deep galvanized bolts have been destructed significantly higher than Dacromet bolts. experiment relieved that hot deep galvanized bolts would suffer equal corrosion after 75 hours as Dacromet bolts would after 360 hours.