Dacromet is actually a trademark of Metal Coatings International, and it describes Dacromet coating Supplier. It is a way of applying a sacrificial coating of zinc. My understanding is it offers higher corrosion resistance than zinc electroplating (probably because it’s thicker).
Salt spray tests are not a meaningful approach to predict the lifestyle of zinc-based coatings though. The security they afford in the real world comes from the development of stable and insoluble zinc carbonate corrosion items that develop with time with contact with the carbon dioxide inside the outside.
“The Ideal Finish” is something the market has sought for many years. It is really an elusive concept where vast amounts of money have already been spent developing, testing and qualifying possible alternative finishes, but most of these efforts have been futile. Each finish, from phosphate to cadmium, has strengths and weaknesses that must be weighed for each application. By using these considerations, progress can be created toward utilizing the materials who have the closest resemblance towards the strengths of cadmium which can be required and, in turn, accepting their weaknesses.
This paper describes a research study conducted on eight finishes which can be potential replacements for cadmium. Details are specific to fasteners in terms of clamp load and corrosion, both cosmetic and galvanic. The scope was broadened to comprehend many elements of each finish to provide engineers information vital to recommending their use as cadmium substitutes and exposing weaknesses of every finish. One inorganic alternative was discovered to be a drop-in alternative to cadmium, and another two were found to closely resemble cadmium’s performance in most respects aside from electrical conductivity.
Because cadmium offers excellent corrosion resistance, consistent torque-tension, bimetallic compatibility and thickness within standard thread tolerances, it has been most engineers’ finish preferred by many years. It really is still utilized in many applications that cannot sacrifice some of the qualities that Zinc Flake Coating offers.
Initially, automotive OEMs established a deadline to eliminate cadmium by 1995. Chrysler enacted testing programs to fill the hole in their fastener finish requirements.1 Chrysler conducted a Form of Experiment (DOE) to qualify alternatives that met strict performance requirements and also followed OSHA and EPA regulations. This DOE led to the selection of the Dacromet 320® L coating system because it closely resembled cadmium in fastener applications. As a result, Chrysler was compliant with OSHA and EPA regulations ahead of the established deadline. Metal Coatings International Inc. (MCII) was involved with this DOE.
Because of the extreme utilization of its equipment in critical situations, the military continued to utilize cadmium for most applications. The delay in switching from cadmium-plated hardware proved beneficial because automotive OEMs compiled much information in that time. The military sorted with the data produced by automotive qualifications and selected zkqjlg coatings that performed well inside the predetermined areas, which in-turn resulted in a substantial cost benefits.
3 years ago, the Army embarked over a cadmium replacement journey, testing numerous finishes as potential candidates.2 Although no “perfect finish” was discovered, this testing resulted in the qualification of a solvent-based coating that closely resembled Coating equipments Manufacturer with regards to corrosion protection, bi-metallic compatibility and clamp load retention. The weaknesses exposed were lack of conductivity, high coating thickness as well as the reliance upon a supplemental lubricant to fulfill Army torque charts. Another attribute that must be considered is the fact this coating was solvent-based and for that reason loaded with volatile organic compounds (VOC). Because of the VOC content, application facilities required expensive air treatment equipment to minimize pollution that otherwise might have escaped in to the environment.