How do I avoid finger marks on passivated zinc plating of mild steel?

A. Fraser,

I don't want to sound like a smart-alec here.. but is wearing gloves MORE impractical, then paying someone to completely re-do your parts? Our company does a lot of work for the semiconductor industry, and we HAVE to wear gloves when handling our finished product. There are powder-free latex gloves on the market that conform to your hands, and don't limit dexterity...remember.. "An ounce of prevention is worth a pound of cure."

A. Not only that, but there is increasing suspicion (no hard evidence that I know of) that repetitive and prolonged skin exposures to chromates (as would be the case for these workers) may be carcinogenic. Wearing of gloves is NOT impractical, Fraser. I've heard it a dozen times, only to see the employees in the shop in question wearing them a few years later.

A. You can ask your supplier to use a water based lacquer after the final rinse as a topcoat over the blue passivation. This will reduce greatly but not eliminate the fingerprinting problem as most of these topcoats are removed by alcohols, oils, solvents. You've got to have clean perspiration-free hands and handle blue parts like photographs, only picking up by the edges.

A. Hi Mark. Thanks for bringing this topic back from hiatus. It has two components, the question of the wearing of gloves, and the question of anti-fingerprint technology.

As for the gloves, I continue to agree with Marc and Khozem, and to say "get used to it". We live in an ever more safety conscious, ever more germaphobic, ever more queasy society; ten times fewer workers go without gloves than a couple of decades ago, and the trend will probably continue until no employee goes without gloves. Most consumers would say "ooh, gross!" if they saw a fingerprint on a new item they purchased.

Anti-fingerprinting technology ranges from the basics to the newest patents. A satin finish on the steel goes a long way to conceal fingerprints; any lacquer or clearcoat that is rough rather than mirror-smooth does the same, as Khozem notes. There are alcohol-based single components sprays that purportedly are effective for a limited life, and presumably fluorocarbon sprays as well.

Manufacturers of display screens have it much harder in that the surface must remain smooth. They apply vacuum coatings like oleophobic fluorocarbon thin films which cause the finger oils to microscopically "bead", thus breaking up the pattern in a similar way to the satin finish. Apple has secured recent patents and the upcoming iPhone6 is rumored to have the best anti-fingerprinting technology yet. But in a way flat-screen manufacturers have it easier than chassis makers because the screen can use a line-of-sight process that won't work on a chassis.

It's probably not a huge technical hurdle to apply anti-fingerprint coatings to chassis, but it can be a cost and logistics issue.

Regards,

Hi again. Hopefully a reader will recognize the type of coating you have explained and was illustrated on letter 1027, and will be able to answer your questions.

Regards,

Looks similar to a "One coat Gray" Teflon to me, which is pretty fingerprint resilient, and can be easily cleaned.

But noticing the electrical properties you are needing, Teflon would not be conductive.