Global Fastener News

1997 FIN – Lowry: No Panaceas in Coatings

April 30
00:00 2012

July 15, 1997 FIN – New requirements for engineered coatings will exclude most conventional finishes, Brian Lowry predicted at an International Fastener & Precision Formed Parts Manufacturing Exposition conference session.

“Today’s fastener requirements in all segments of the industry have become so advanced that traditional finishes such as zinc plate, phosphate & oil and even longtime standard coatings such as black organic and oil can no longer meet expectations,” said Lowry, vice president for technical services at Curtis Metal & Finishing Company.
Corporate mandates include “extreme durability, friction-modification, galvanic protection, versatility, cleanliness, cost effectiveness and environmental friendliness.”
Lowry said, “there is not one single product that will meet all the needs that may be desired in any industry. There are no panaceas.”
Most new finishes “have been born out of the automobile industry,” Lowry reported. “This industry provides the most diversity of environments that a fastener may be exposed to-cars run in the sun, rain and snow. Cars run on clear pavement, dirt roads and mud,” Lowry noted. “Chassis components are exposed to dirt, road salt and gravel, underhood components see elevated temperatures and exposure to various automotive fluids.”
Even interior fasteners “see swings in atmospheric temperatures and humidity, and mate to a variety of materials including many types of plastics.”
The three driving forces behinds automotive coating changes are torque/tension assembly performance, corrosion resistance and cost effectiveness.
“When any joint is designed, the primary consideration of the fastener engineer is that the proper amount of load is applied to the fasteners,” Lowry said. Finish affects the amount of friction, protects the bearing surface and provides any barrier between the fastener and material it mounts against, and protects the metal fastener from the surrounding environment.
The newest automotive standards include test procedures and windows for torque/tension performance. Lowry pointed out.
Corrosion resistance requirements such as Ford’s 4-6-10 (4 years cosmetic, 6 years serviceability- and 10 years minimum joint protection) “have elevated performance standards to all-time highs,” Lowry finds. New products are evaluated using methods beyond ASTM B117 salt spray testing. Testing is designed to simulate actual vehicle life.
“A likely correlation can be made that any finish that could survive the severity of this type of testing could be used in any number of industrial applications with similar exemplary performance,” Lowry said.
Several zinc-rich and aluminum-rich coating products applied to fasteners used in chassis applications have passed the tests, Lowry said.
Zinc alloy electroplated fasteners perform well in salt spray but fail in underbody applications due to chipping potential. Paints, oil and phos/oil products “meet a similar fate due to the wash-away of the oil protectant.”

Cost Effectiveness
Meeting “any and all performance requirements” doesn’t automatically grant the supplier “a blank check for pricing,” Lowry said.
The highly competitive, now global” automotive industry has suppliers “working under significant price restraints.”
“Selection of a particular finish may hinge on its cost stability as opposed to competing processes,” Lowry said. “When factoring in all the costs of zinc electroplating fasteners- plate, bake or chromate-engineered coatings are very competitive and offer more ‘bang for the buck'”.
“Never before has there been as much cooperation in North America and Europe in the development of common specifications,” Lowry said.
The United States Coalition on Automotive Research (USCAR) and the Automotive Industry Fastener Group (AIFG) “are seeking to rationalize the specification and use of fasteners for automotive use.”
Organic coatings have the advantages of durability, torque consistency and freedom from hydrogen embrittlement but are unavoidably thicker. The newest engineered coatings “offer thickness only moderately heavier than their electroplated counterparts,” Lowry said.

Environmental Friendliness
“Environmental regulations are spurring the growth of engineered coatings,” Lowry explained.
The elimination of cadmium at automotive and the continued replacement of this workhorse finish in other industries, including the military, will have a profound impact on the types of products specified for the future.”
Environmental standards vary between nations. Cadmium concerns began in Sweden in the mid-80’s and didn’t take hold in the U.S. until the early ’90’s.
Today aerospace and the military still use cadmium, “but you won’t find it in a car,” Lowry said.
There is “potential for a call for the elimination of chrome and chromates worldwide,” he added. ©1997/2012 Fastener Industry News
For information on permission to reuse or reprint this article please e-mail: FIN@GlobalFastenerNews.com

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