Fasteners and Finishes

Article From: Products Finishing, from Technical Presentations Co

Posted on: 10/1/1999

Automotive fastener finishing is a major market in the Midwest and globally, although there are many more non-automotive fasteners used every day than car fasteners.

Automotive fastener finishing is a major market in the Midwest and globally, although there are many more non-automotive fasteners used every day than car fasteners. While car and truck companies have their own likes and dislikes and dictate the market for their product, numerous other coatings and finishes exist and function very well, making life a bit better for a vast number of people who are basically unconcerned about cars.

I have been asked to review many coatings for fastener applications in markets other than automotive. Occasionally I will write about these, sometimes as a type or sometimes as a specific product that should have a closer or even a second look. While much of the information about these products will come from the manufacturer, I will review and write my opinion about them. The written pros and cons of these products will reflect my judgment based on more than 40 years of experience in the fastener-engineering field and, when required, whatever testing that I feel is necessary to prove a point. The necessary disclaimer is that the opinions stated are my own and do not necessarily reflect the thoughts or opinions of those working at Products Finishing magazine. With that done, let me ask that any coating manufacturer with a new idea or coating contact me at techpres@rust.net or fax me at 810-939-0032 with their product information.

I will choose the coatings that have potential for fastener use, represent a type of application or chemical that I feel should have a closer look at by the industry or is just an item that the readers may find interesting. Often ideas exist but never get their "15 minutes." I hope to air a few here from time to time.

With that introduction, I would like to comment upon a coating with great cost saving potential. Often I have watched parts come from the heat treatment furnaces, fall into the quenchant and mused that a lot of expensive energy was used to generate heat that was just lost. Several coatings use some residual heat to dry the coating, but a newer coating saves money by using the heat from the treated parts as part of its process.

Called Thermadepsm, and offered by The Egyptian Lacquer Mfg. Co., the coating has had use in a variety of applications, including castings, stampings, steel components like cabinets, furniture, aeronautical and agricultural equipment. Compression springs and some automotive areas have had particularly good success with it. The basic coating chemical is a waterborne polymer in which parts are quenched. Temperatures from 300 to 1,700F may be used. The part is quenched for 5 to 50 seconds and removed, allowing the retained heat to complete the process and dry the parts. No additional steps and no post-quench rinses are needed. I reviewed this process with some manufacturers of high-carbon spring steel clips that austemper their parts (quench in molten salt). They indicated that they saw no problem with this as the parts could be removed from the molten salt at about 600F, rinsed and finished by quenching in the Thermadep.

Water based in nature, the process is environmentally friendly, greatly reduces cleaning, degreasing, labor and handling of solvents and cleaning chemicals. It is relatively inexpensive to set up and run too. The basic equipment requires low capital investment, consisting of a tank to quench the parts, a removal conveyor and a secondary conveyor to allow the parts to dry 2-3 minutes before packaging. Process controls are simple and require that solids be maintained as the chemicals are formulated for extended use. The coating is available in 15 colors, including gold and clear. Yes, black is available as a low-gloss product free of runs, tears and sags and blisters.

Limited use has been made of the coating for fasteners so far, but the potential is there. One drawback is that the salt spray life is in the 48-72 hour range, which equates to about nine months real world. That is, if salt spray equates to any real condition Thermadep parts used in agricultural areas have shown little corrosion after two years in use. Humidity ratings of 200-300 hours protection are standard (ASTM D2247).

If you have an idea or an interesting coating or finish for fasteners, email me at techpres@rust.net or fax me at 810-939-0832. Include your address and if samples are available.

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