FASTENERS • SEALING
STAINLESS STEEL
Michael Pasko explores the advantages of employing 420 chrome stainless steel coiled spring pins across diverse applications
pirol invented the Coiled Spring Pin in 1948 and are used in companies developing automotive, medical, heavy
S
WONDERS Oiled Spring Pins are
off ered in light, standard and heavy duty to meet application-specifi c requirements
are inherently corrosion resistant. Platings
equipment, military, aerospace, and consumer products. In applications requiring a combination of high strength, superior fatigue life, and corrosion resistance, 420 martensitic chrome stainless steel off er a host of technical benefi ts and provides an overall robust cost-eff ective solution.
HIGH STRENGTH Spirol’s 420 stainless steel Coiled Spring Pins are hardened to values approximating their high carbon steel equivalents and share the same minimum rated shear strength. This process also develops desired spring properties and fatigue resistance. Chrome stainless steel Coiled Pins
also off er good corrosion protection against most common atmospheric and environmental conditions without the risk of rapid work hardening associated with 302/304 austenitic stainless steel. In most cases, companies may use 420 chrome stainless steel Coiled Spring Pins as drop-in replacements for high carbon steel pins assuming galvanic potential has been considered relative to the host material.
CORROSION RESISTANCE When companies require corrosion resistant Spring Pins, there are two common options: carbon steel with a sacrifi cial protective plating or coating or stainless steel alloys which
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and coatings provide excellent performance though they are consumed over time, whereas stainless steel provides a lifetime of protection providing free oxygen is available in the environment (free oxygen allows the fastener’s protective chromium oxide layer to reform if damaged). For plated and coated parts, once the plating or coating is depleted, the carbon steel is left unprotected and rapidly corrodes. 420 martensitic chrome stainless
steel also provides good corrosion resistance in environments, including, but not limited to, normal
atmosphere and humidity, steam, fresh water, alcohol, ammonia, alkalis, mild acids (e.g., carbonic), petroleum products
such as gasoline, oil, crude, and mild detergents and sterilising solutions. While 302/304 austenitic stainless
steel Coiled Pins provide excellent corrosion protection, this material is not an appropriate solution when the pin will be subject to dynamic loads, or where strength and fatigue resistance must equal or exceed that of high carbon steel. Alternatively, 420 martensitic chrome stainless steel provides an exceptional combination of strength and fatigue resistance – in addition to its inherent corrosion resistance.
This graph shows how time impacts the corrosion resistance of coated steel compared with stainless steel
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