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Lasting Fastening

About Stainless Steel Screws, Nails, and Staples from Columbia Fasteners

AISI 304, 305, and 316 Stainless Steel

Beyond Appearance

The upgrade to stainless steel fasteners is a minor consideration to the total materials cost of your building project! Protect your investment with premium high quality fastening products from Columbia Fasteners. Quality stainless steel products provide cost effective insurance and improve the aesthetic value of your craftsmanship. Exposure to extreme weather conditions, high moisture levels, salt air or other caustic conditions pose a serious threat to both wood–and wood substitute–based construction applications alike. Solid stainless steel fasteners are not subject to corrosion most commonly caused by breaches or failures in surface finishes found on galvanized and coated fasteners. In addition to corrosion of fasteners that weakens structural integrity, unsightly staining, streaking and discoloration of galvanized and coated fasteners devalues the quality of the workmanship. Given the high costs of labor, lumber and other building materials, the inconsequential cost of top quality stainless steel fasteners insures greater protection for your investment.

Graded Stainless Steel Alloys

Top-grade stainless steel alloy fasteners (as designated by the American Iron and Steel Institute, AISI) is considered the standard of the construction industry. The products labeled with specific alloy grades in Type 316, 305, 304 are the industry’s stainless steel standards to help users determine the ideal grades specific to the job requirement. Stainless steel is comprised of iron base alloys containing a minimum of 11.5% chromium. This presence of chromium is key to stainless steel’s corrosion resistant qualities–as it combines with oxygen to form a tough, thin, clear passive film of chrome oxide on the metal’s surface, insulating the alloy against caustic attack. Even when the metal is cut or scratched, the oxide is quickly formed and recovered to protect against oxidative corrosion. Iron, on the other hand, does not have this self-repairing passive film, and will lead to degradation and oxidation—resulting in rust.

Type 304, 305 and 316 grade stainless steel are inherently non-magnetic, nickel/chromium Austentic grades. The varying composition of the alloys determines its grades and mechanical properties. The mechanical properties of these alloy grades are enhanced through wrought processes such as cold heading and roll threading. Types 304 and 305 provide adequate corrosion protection for most construction applications. Type 316 contains slightly more nickel than 304 and 2-3% more molybdenum, giving it extra resistance to corrosion, especially in high chloride, salt-environments to protect against pitting. Type 316 offers superior performance when exposed to sea water and high sulfuric acid environments. In general, Type 316 fasteners is strongly recommended for exposed seaside applications.

Nail Strength

Carefully controlled tests of nail strength and shear loading properties show that stainless steel and plain steel nails have about the same stiffness (+/-5%), although the ultimate lateral loads for stainless nails are about 20% higher than comparable plain steel fasteners.

The following table presents main elements (forming the Chemical composition) of AISI 316, 305, and 304 Grade Stainless Steel as compared to other cheaper grade steel such as 302 and 200 that exist in the market as “stainless steel” and its significance.

Nominal Composition of Stainless Steel

CHEMICAL ELEMENT201 SS302 SS304 SS305 SS316 SSSIGNIFICANCE
Ch - Chromium 16-18% 17-19% 18-20% 17-19% 16-18% * +11.5% forms stainless steel from ordinary steel, neutralizes the corrosive effect of carbon* Ch forms a passive film which prevents oxidation & corrosion
Ni - Nickel 3.5-5.5% 8-10% 8-12% 10-13% 10-14% * Nickel provides corrosion resistance, increases strength in both high & low temperature, increases toughness in low temperature and lowers the effects of work hardening * Higher Ni % makes superior quality steel
C - Carbon .15% Max .08-.15% .08% Max .08% Max .08% Max * Higher carbon % decreases corrosion resistance
Mo - Molybdenum (Moly) X X X X 2-3% * Moly helps resist corrosion to chlorides & sulfates found in sulfurous acids used in pulp industries * Has a superior tensile strength at high temperature as compared to 304 Grade steel * Moly can resist corrosion by major chemical reaction, but can be costly
Mn - Manganese 5.5-7.5% X X X X * Increase in Mn ratio decreases the corrosion resistance
Fe - Iron Balance Balance Balance Balance Balance * Increase in iron ratio decreases corrosion resistance

 

To summarize, fastener selection is critical in matching the correct alloy with the application. Stainless steel is corrosion resistant, not corrosion proof. AISI 304, 305, and 316 Grade Stainless Steel provides the best in corrosion resistance in most outdoor applications. The lower grades like 302 and 200 series are stainless steel by name, but do not provide adequate resistance to corrosion. The least expensive type 200 stainless steel has inferior corrosion resistance and material durability. Columbia Fasteners carries quality stainless steel products of the highest industry standards.