Knowledge Base

Stainless steel fasteners are made from a steel alloy that contains a minimum of 10.5% of Chromium and is also referred to as Inox steel. There are over 150 different grades and surface finishes of stainless steel fasteners and stainless bolts that are available. The type of stainless steel fastener used should be engineered for the application/environment that it is being used. However, the two most common grades are 304 stainless fasteners (commercial grade) and 316 stainless fasteners (marine grade). For simplicity sake, many treat type 304-ss fasteners and type 18-8 ss and A2 ss fasteners as nearly identical materials and are often used interchangeably / synonyms.

Glossary of terms for screws & fasteners

Learn key differences between fine thread and coarse thread screws to distinguish your preferred option

Corrosive damage is pertinent to all construction jobs and should therefore be accounted for during the design phase of any project. Often observed as “rust”, corrosion is the progressive deterioration of metals through an oxidation process. In practice, corrosive damage results in an unpleasant building appearance, compromises structural integrity, and damages internal building structures. Fortunately, proper project planning can absolve architects, designers, and contractors of these potential issues

Rivets offer contractors numerous benefits: easy and efficient installation, lasting durability, and lower costs. However, when it comes to selecting the best rivets for your project, there’s no room for error. Choose the wrong size, and it will be impossible to install or the strength of the connection will be compromised. Choose the wrong material, and the rivets’ integrity may diminish with time. Below are points to consider when determining ones to buy

Fasteners come in all shapes and sizes, and it’s a contractor’s responsibility to identify the optimal screw length for the specific job. The following guide will help you determine the correct length based on the type of connection and depth of the material

Metal roofing is typically installed in either a standing seam or exposed fastener configuration. Although both systems provide the advantages of a metal roof, each respective system has distinct pros and cons

When stainless steel is seen in a specification or recommendation for fastener applications, it’s most likely referring to 400-series or 300-series alloys (most commonly, 410 and 304).  Both are incredibly strong and offer respectable rust resistance, there are game-changing distinctions between the two. In this article, we’ll highlight how 300 and 400 stainless steels compare regarding composition, performance, and pricing to help you ultimately determine the best option for your next build. What defines 300 vs 400 stainless steel series?    You may also see 400-series be referred to as martensitic stainless steel and 300-series referred to as austenitic stainless steel. The biggest difference between these groups of alloys is the chemical composition (the ratio of different elements that create the metal).  More specifically, the two groups of alloys have varying amounts of chromium and nickel.   304 stainless steel, the most common alloy for 300-series fasteners, contains around 50% more chromium than 410 stainless steel, the most common alloy for 400-series stainless steel fasteners. And while 410 stainless steel does not contain any nickel, nickel makes up around 10% of the total composition of 304 stainless steel.    While chromium and nickel are the primary differentiators of 400-series and 300-series stainless steels, molybdenum can be added to 304 stainless steel to create 316 stainless steel, making up around 2.5% of the total composition.   The important thing to remember is that both chromium and nickel work together in stainless steel to increase corrosion resistance! How 300 series screws compare to 400 series for corrosion strength   410 stainless steel offers mild corrosion resistance thanks to its chromium content, and is commonly used in applications where the fasteners will not be exposed to constant moisture or any chemicals. An example of an application where 410 stainless steel may be used is metal wall panel attachment.    However, 304 stainless steel offers some of the best corrosion properties that are available for fasteners thanks to the amount of chromium and nickel that are in the alloy. 304 stainless steel can be used in the presence of a variety of chemicals and acids; including lower concentrations of chlorides (salt). When choosing a fastener that will regularly come in contact with moisture, chemicals, animal waste, and low concentrations of salt, 304 stainless steel is the best option!   With the addition of the molybdenum, 316 stainless steel becomes much more resistant to chlorides and harsher chemicals. When choosing a fastener that will come in contact with chemicals such as sulfuric acids and higher concentrations of salt that are present within 1km of the ocean, 316 stainless steel is the best commercially available option!   Which type of stainless steel is stronger – 300 or 400?    Because of the differences in composition, 400-series stainless steels can be heat treated to higher hardnesses while 300-series stainless steels cannot. This enables 410 stainless steel fasteners to be much harder than any 304 stainless fastener, and thus stronger. In applications where ultimate tensile or shear strength is critical, 410 stainless steel fasteners may be preferred.   How does pricing compare between 300 series stainless vs. 400?    Simply comparing raw materials, 304 stainless steel is around 50% more expensive than 410 stainless steel. In turn, this often results in most 300-series fasteners being more expensive than their 400-series counterparts. Therefore, we often direct customers towards 400 stainless steel if the anticipated exposure to corrosive elements is low. However, in scenarios in which external corrosive elements will be high, we encourage buyers to think of the long-term savings that come from fasteners with inherent resistance to rust (300-series) rather than those which will compromise the integrity of the build.    Don’t forget about galvanic corrosion when choosing a stainless steel screw   One topic that is often overlooked during fastener selection is galvanic corrosion, specifically when aluminum is used. When a fastener is being used in an application where aluminum is present, extra caution needs to be taken to limit galvanic corrosion within the connection. Galvanic corrosion is caused when dissimilar metals come in contact with an electrolyte, like water. If this is not prevented, a phenomenon called hydrogen assisted stress corrosion cracking can occur which essentially causes cracking of hardened steel, like hardened 410 stainless steel. Due to the lower hardness of 304 stainless, which may have seemed like a hindrance, actually means that it is immune to this phenomenon. Therefore, when aluminum is present in an application, 304 stainless steel is the best choice for fastener material!

Stainless steel (SS) fasteners are utilized in the construction industry to satisfy corrosion resistance and strength requirements. This document analyzes the properties of two popular types of stainless steels—304 versus 316—as well as which materials are best suited for metal-to-metal connections Stainless steels are commonly offered in nine grades categorized by materials added to the steel during production. The resulting alloys have different materials, strength, and corrosion properties. Alloy grades 304 and 316 are by no means the only steels featured within SFS’s line of fasteners, but they are some of the most in-demand amongst builders. 304 versus 316 stainless steel: differences in composition 304 SS is considered a “general purpose” stainless steel and is characterized by the inclusion of 18% chromium (Cr) and 8% nickel (Ni) in its’ alloy composition. In contrast, 316 Stainless steel is characterized by the inclusion of 16% chromium (Cr), 10% nickel (Ni), and 2% molybdenum (Mo). The presence of molybdenum provides added strength, as further explored below. 304 versus 316 stainless steel: differences in corrosion Stainless steel in general offers significant corrosion resistance when compared to standard carbon steel materials. Within the stainless steel classifications, there are grades that will outperform others. The Increased nickel content in 316 SS contributes to its improved corrosion resistance compared to 304. As such, 316 is recommended for use in coastal regions where there is an increased salt content, or in areas where there are higher levels of pollution or corrosive chemicals, particularly chloride. 304 versus 316 stainless steel: differences in strength While both 304 and 316 stainless steel are strong, the addition of the Molybdenum in the 316 gives it a small advantage in strength over the 304. The following table displays the characteristics of the two materials. From Table 1, it can be seen that the 316 stainless steel offers greater yield strength (where the material becomes permanently deformed) and decreased elongation and tensile strength. There is little difference between alloys when it comes to strength, but corrosion resistance is where the 316 truly surpasses the 304. Table 1: Displays the strength characteristics between 304 and 316 stainless steels. Note that the information in this table does not represent the strength of SFS fasteners, but rather the raw material properties. Cost analysis Another difference between the 304 and 316 is the cost of the material. When made into fasteners, the 304 SS tends to be more affordable. For this reason, 304 SS products are more popular among consumers. It meets standard corrosion requirements at a lower cost than the higher grade material.  Alternatively, 316 SS fasteners tend to be used by contractors who operate in highly corrosive environments.  Other stainless steel grades 304 and 316 stainless steel fasteners are not the only material options available for consumers. While the 300 series offers superior corrosion resistance, the 400 series provides an elevated hardness. For example, 410 SS has a low alloy content, meaning that there are fewer materials added to its composition, resulting in a higher carbon content. This increased amount of carbon gives the 400 series of stainless steels increased strength characteristics as well as better performance at elevated temperatures while still maintaining some corrosive resistance. Due to the lower alloy content in the 400 series of stainless steel, fasteners made from this material tend to cost less than the 300 series parts. Material selection guide Review the tables below to learn more about 304, 316 and other popular SS grades to determine the optimal choice for your upcoming project. Environmental Conditions The following chart describes the environmental conditions in which certain grades of stainless steel are appropriate. All environmental conditions are based on EN ISO 12944 Exposure Categories. Results based on SFS internal testing and supplemented by The Nickel Institute, “Design Guidelines for the Selection and Use of Stainless Steel” (Released by AISI). Table 2: Material selection based on environmental conditions.  ✔ indicates fastener material is recommended for the described environmental conditions ✔* indicates faster material is recommended with explicit approval of specified application Environmental condition explanation Environmental grades are taken from ISO 12944. They do not describe specific quantitative criteria for pollution levels, but are instead meant to be standard guidelines for generalized environmental conditions. Material connections The following chart describes the situations in which a fastener of a particular material can be installed into a surface of a particular material. The information from this chart is derived from the MCA technical document, “Fastener Compatibility with Profiled Metal Roof and Wall Panels”.  Table 3: Material selection based on cladding material being used.  ✔ indicates fastener material is recommended for the described Cladding Material   Summary of 304 vs 316 Stainless Steel Stainless steel fasteners can offer a wide variety of strength and corrosion-resistant properties to meet your requirements. Each grade of stainless steel will have different properties and provide advantages in particular environments. It is important for contractors to choose the correct material for their fasteners based on their job site environment. This document serves as a tool to help effectively make the correct fastener selection based on your needs.

The many unique benefits of stainless steel make it a powerful candidate in materials selection. Engineers, specifiers, and designers often underestimate or overlook these values because of what is viewed as the higher initial cost of stainless steel. However, over the total life of a project, stainless is often the best value option. What is Stainless Steel? Stainless steel is essentially low-carbon steel that contains chromium at 10% or more by weight. It is the addition of chromium that gives the steel its unique stainless, corrosion-resisting properties. The chromium content of the steel allows the formation of a tough, adherent, invisible, corrosion-resisting chromium oxide film on the steel surface. If damaged mechanically or chemically, this film is self-healing, provided that oxygen, even in very small amounts, is present. The corrosion resistance and other useful properties of the steel are enhanced by increased chromium content and the addition of other elements such as molybdenum, nickel, and nitrogen. There are more than 60 grades of stainless steel. However, the entire group can be divided into four classes. Each is identified by the alloying elements which affect their microstructure and for which each is named. Stainless Steel Grades and Applications 400 Series Martensitic – Typical grade: 410 Straight chromium (12 – 18%); magnetic and can be hardened by heat treatment. Typical use: Fasteners, pump shafts. 400 Series Ferritic – Typical grade: 430 Straight chromium (12 – 18%); low carbon, magnetic, but not heat treatable. Typical use: Appliance trim, cooking utensils. 300 Series Austenitic – Typical grade: 304 Chromium (17 – 25%), Nickel (8 – 25%); nonmagnetic, not heat treatable. Can develop high strength by cold working. Additions of molybdenum (up to 7%) can increase the corrosion resistance. Typical use: Food equipment, chemical equipment, architectural applications. Precipitation Hardening – Typical grade: 17-4 Chromium (12 – 28%), Nickel (4 – 7%); martensitic or austenitic. Develop strength by precipitation harden reaction during heat treatment. Typical use: valves, gears, petrochemical equipment.   The Many Benefits of Stainless Steel Corrosion Resistance – Chromium is the alloying element that imparts to Stainless Steel their corrosion-resistant qualities. Lower alloyed grades resist corrosion in atmospheric and pure water environments; high-alloyed grades can resist corrosion in most acids, alkaline solutions, and chlorine bearing environments making their properties useful in process plants. Fire and Heat Resistance – Special high chromium and nickel-alloyed grades resist scaling and retain high strength at high temperatures. Stainless Steel is used extensively in heat exchangers, super-heaters, boilers, feedwater heaters, valves, and mainstream lines as well as aircraft and aerospace applications. Hygiene – Cleanliness is a matter of high importance. The easy cleaning ability of stainless makes it the first choice for strict hygiene conditions, such as hospitals, kitchens, and food processing plants. Aesthetic Appearance – The bright easily maintained surface of stainless steel provides a modern and attractive appearance. Strength-to-Weight Advantage – The work-hardening property of austenitic grades results in a significant strengthening of the material from cold-working alone, and the high strength duplex grades, allow reduced material thickness over conventional grades yielding considerable cost savings. Ease of Fabrication – Modern steel-making techniques mean that stainless can be cut welded, bent, formed, machined, assembled, and fabricated as readily as traditional steel. Impact Resistance – The austenitic microstructure of the 300 series provides high toughness at elevated temperatures ranging far below freezing, making these steels particularly suited to cryogenic applications. Long-Term Value – In considering total cost, it is appropriate to consider material and production cost AND the life cycle cost. When the total life cycle costs are considered, stainless is often the least expensive material option. The cost-saving benefit of a maintenance-free product having a long life expectancy. 100% Recyclable – Over 50% of new stainless comes from old remelted stainless steel scrap, thereby completing the full life cycle.