Understanding stainless steel and the different grades.

In this blog we will investigate the differences between 304 & 316 grade stainless steel in relation to structural and standard rivets. To the naked eye, you are not able to see the different grades of stainless, however the difference will make itself more apparent over time. In this beginner’s guide to Rivets - Stainless 304 Vs 316, we will investigate the differences between the grades as well as suitable applications. Before we begin, let’s start with the basics. 

Stainless steel is an iron-based alloy containing chromium, which forms a thin, protective oxide film on the surface that helps resist corrosion. However, stainless steel is not completely rust-proof. Its corrosion resistance depends on several factors, including exposure to salt and chlorides, temperature, crevices, surface contamination and maintenance. Other alloying elements, such as nickel and molybdenum, contribute to the different properties of stainless steel grades, including 304 and 316.

The most basic difference between grade 304 and grade 316 stainless steels is that 316 tends to have more nickel and a bit of molybdenum in the mix, which makes it considerably more expensive. The increased nickel content and the inclusion of molybdenum allows for grade 316 stainless steel to have better chemical resistance than the 304 stainless steels. Its ability to resist acids, chlorides, including salt, makes grade 316 ideal for numerous chemical, food, and marine applications. Most of the Huck Aerobolt range of fasteners indicate the grade of stainless including rivets, nutserts, rivnuts and so much more. The structural rivets range with more than one grade of stainless includes Magna-Lok, Allok and Orlock rivets.

What Are the Benefits of Stainless Steel? 

Stainless steel has numerous advantages over other metals including corrosion resistance, durability, aesthetics and so much more.   

• Corrosion Resistance: Especially when you are using products that come into regular contact with water both in liquid and vapour form, inclusive of fresh and sea water, corrosive chemicals, food preparation or medical applications. This includes sterilization processes that involve heating with disinfectants and other cleaning chemicals. 

• Hygiene: This a high-stakes benefit, especially when it comes to restroom / bathrooms fixtures, food preparation areas, food display cabinets, and associated accessories like water coolers/bottle fillers. 

• Durability: Stainless steel offers excellent durability, strength and corrosion resistance when the appropriate grade is selected for the application. Its long-term performance depends on environmental conditions, surface preparation, maintenance and the specific fastener design.

• Aesthetic Appearance: This metal is attractive on its own, whether it’s polished to a high shine or has a satin finish. 

When to use stainless steel 316 over 304? 

If your application involves corrosive substances such as chloride, marine, or medical environments then paying a premium for grade 316 stainless steel is worth it. In such work applications, the 316 stainless steels will last longer than 304 stainless steels—this means many extra years of useful life. For other applications where salt or water exposure isn’t a concern, the stainless steel 304 alloy can work just as well. Just be sure you’ve accounted for all processes and environmental factors when choosing the material. For instance, if the application is located on or near the coast, salty sea air can corrode metals. Overall, 316 can be worth the expense if you need to have superior corrosion resistance. For many other applications, grade 304 stainless steel will serve perfectly fine.

Another key difference between the different grade stainless steels is the melting point of grade 304 stainless steel is a bit higher than that of grade 316. The melting range of grade 316 is 1,371 °C – 1,399 °C, roughly 50 degrees lower than the melting point of grade 304 stainless steel. Plus the tensile strength of 304 stainless steel is a little better than the 316 grade.  

What are the stainless-steel applications? 

Common applications for stainless steel: Cisterns and piping used in chemical applications, Commercial kitchens and appliances, Containers used to hold pressurized gasses or liquids, Equipment for chemical storage and processing, Equipment used for industrial and chemical transportation, Marine components, Marine settings, Medical devices and equipment not requiring surgical steel, Outdoor electrical enclosures, Outdoor furnishing, Pharmaceutical manufacturing, Refinery infrastructure, Seafood production and other food processing in saline environments. Stainless steel floats. 

What are the benefits of 316 stainless steel? 

316 grade stainless steel has several advantages over 304 stainless steel this is due to the 16% chromium, 10% Nickel and 2% molybdenum composition. The benefits include.   

Better Corrosion Resistant Properties.  

Due to the addition of molybdenum, grade 316 stainless steel is more corrosion resistant than similar alloys, such as 304 stainless steel. This reduces pitting from chemical environments and allows grade 316 stainless steel to be used in highly acidic and caustic environments that would otherwise eat away at the metal. For instance, grade 316 stainless steel can withstand caustic solutions and corrosive applications such as vapor degreasing or many other parts cleaning processes.

These properties also make grade 316 stainless steel ideal for pharmaceutical and medical applications. Since sterilization processes in these industries combine both strong disinfectants and or with high temperatures to prevent contamination, a resistant alloy such as grade 316 is ideal. 

Superior Resistance to the Effects of Salt Water.

Seawater and salt air can be especially damaging to metals. Besides the rough environment of the marine applications, chlorides, such as salt, can eat away at even the toughest metals. Salt will even compromise the protective oxide layer of grade 304 stainless steel, resulting in rust.  For marine applications, or processes involving chlorides, grade 316 stainless steel is ideal.

Grade 316 has especially better resistance to salt and chloride pitting. Pitting corrosion can occur when stainless steel alloys, such as grade 304 stainless steel, meet salt-rich sea breezes and seawater. Chloride resistant metals, like grade 316 stainless steel, are essential to use for naval applications or anything involved with chloride. 

Long Lasting Durability.    

Grade 316 stainless steel is both tough and versatile, designed to even survive repeated exposure to high impact processes.

Frequently Asked Stainless Steel Rivet Questions.

How do I order rivets?

There are number of different type of rivet code formats. At Aerobolt we use the same product code as "Marson® Rivets" which is a division of Howmet Aerospace.  Rivet code begins with the "body material", followed by the "head type","body diameter" dash & then "grip range" (both of which are representive numbers, rather than actual measurements). The code concludes with the pin material. 

In the above product code example (in the red box), beginning from left to right we have:

A = Aluminium body material. Other options include (S = Steel, SS = Stainless, etc.).
B = Button / Dome Head. Or you can select (T/LF = Truss/Large Flange, C = Countersunk) 
6 = 4.8mm (3/16") body diameter. Other options are; 4 = 3.2mm (1/8"), 5 = 4.0mm (5/32"), 8 = 6.4mm (1/4").
6 = 7.9 - 9.5mm this is the material grip range. See grip codes number table in previous section. 
S = Steel pin/mandrel material. The other options are (SS = Stainless, A = Aluminium etc.).

How do I remove a rivet?

Rivet removal is straight forward with the right tools. This requires the destruction of the rivet, and the best method is to drill it. You will need, a drill, drill bit, long nose pliers, & safety accessories such as glasses and gloves.

Steps: Use your safety glass & gloves before starting the drilling process. Place the drill bit against the rivets’ center pin and drill through the body at a low but steady speed. Once drilling is completed, pull the rivet off with your long nose pliers. How easy was that!  

How do I install a rivet?

To install a rivet is simple with practice, pre drilling of holes is required. Load rivet’s pin tail section into rivet gun. Insert rivets body into hole and activate gun. Upon activation the head of the rivet is pushed against the outer surface of the tool, whilst the tool pulls up the central pin. As a result, the bottom portion of the rivet compresses, and expands on the blind side. This expansion increases until it reaches approximately one and a half times the size of the original diameter. Resulting in a larger surface in which the two materials are effectively fastened together.

How does a rivet work?

How rivets work is ingenious. Essentially a rivet is composed of two components, a metal tube (body) & pin (mandrel). The pin is normally longer than the tube and designed to be pulled up through the tube whilst enlarging it in the process. This results in the expanded tube clamping the material between the two ends of the tube. See the image below to better understand how a rivet works.

 

Which is the best rivet gun?

Selecting the correct rivet gun depends on several factors that relate to your specific requirements, rivet gun section is covered in the blog; Ultimate Guide to Rivet Guns.

Which is the strongest rivet? 

Structural blind rivets are the strongest option on the market due to the unique combination of internal pin retention & locking mechanism that creates their inner strength. Aerobolt has the complete Huck Structural Rivet range including the original multi-grip rivet "Magna-Lok", the Huck Rivet "Magna-Bulb" with its superior installation values and the hybrid of the two "Hucklok Rivet". The strongest structural rivet option is  Huck Rivet "Magna-Bulb" refer to the table below to compare a range of structural rivet's lab results.

STRUCTURAL RIVET TYPE		KEY LAB METRICS FOR STEEL 6.4MM (1/4")
		Shear Typ. (kN)	Tensile Typ. (kN)	Grip Range (mm)
Magna-Lok® (HRDS-0806)		11.1	8.2	2.0 – 9.5
Hucklok® (HKLP-R8-6)		15.6	8.5	2.0 – 9.5
Magna-Bulb® (MBDS-0806)		16.0	8.9	5.8 – 7.8
Allok® (ARDS-08145)		13.7	7.9	5.0 – 8.5

Can I get coloured rivets?

Yes, painted rivets are available. They cost a little extra compared to the mill (raw) finish and are available in a wide range of colours. Refer to the Colorbond ® colour chart for your selection. 

Why Has My Stainless Steel Rivet Rusted?

Stainless steel rivets offer excellent corrosion resistance, but they are not completely rust-proof. Rust staining can occur for several reasons and does not necessarily mean the rivet has failed.

Mandrel Material: Some stainless steel blind rivets contain a carbon-steel mandrel, which may rust when exposed to moisture. For improved corrosion resistance, consider a rivet with both a stainless steel body and stainless steel mandrel, ensuring the selected materials suit your application.

Surface Contamination: Steel filings, drilling swarf or contact with carbon-steel tools can leave contaminants on stainless steel surfaces, causing rust staining.

Dissimilar Metals: Contact between different metals in the presence of moisture can cause galvanic corrosion, potentially affecting the rivet or surrounding materials, depending on the metal combination.

Stainless Steel Grade: Grade 304 stainless steel can develop surface staining or pitting when exposed to salt, chlorides or harsh environments. Grade 316 offers improved resistance to chloride-related corrosion, making it a better option for many coastal and demanding applications. However, neither grade is completely corrosion-proof.

When selecting stainless steel rivets, always check the material grade of both the rivet body and mandrel, along with the environmental conditions and installation requirements.

Explore our all-stainless steel rivets or 316 stainless steel body rivets with 304 stainless steel mandrels to compare available options.

If you're unsure why your rivets are showing signs of corrosion, contact Huck Aerobolt with the rivet part number, photographs and installation details. Our technical team can help review your application and discuss rivet testing laboratory services where appropriate.

When is it better to use a rivet rather than a bolt and nut?

Bolts & nuts offer a useful combination of strength & convenience, and are an ideal solution in static applications i.e. where movement is at a minmum. The disadvantage of these fasteners is their poor resistance to vibration, this means over time they loosen and lose their grip. Huck bolts and Huck's structural rivets have overcome the issue of loosening, so in this instance the right answer is in the application.  

Who invented the blind rivet?

In 1934 the George Tucker Eyelet Co. was approached by an aircraft manufacturer to develop a fastener that could be set from just one side of the material. This lead to the world famous POP® rivet—named for the “popping” sound it makes during installation—which is now owned by Stanley Engineered Fastening, a division of Stanley Black & Decker.

Whats the difference between a pop rivet & blind rivet? 

This is a popular question that many customers ask. The short answer is there is no difference between Pop® rivets, pop rivets, and blind rivets. These are different labels for the same item, a blind rivet means you do not need access to the other side of the material, or you can't see the other side of the material. Also known as pop rivets because this is the name of the original rivet company-Pop® and this is the sound rivets make when installed.   

Why are rivets used on airplanes?

Rivets are preferred for the construction of airplanes because they can withstand extreme stress. They are said to withstand extreme stress without breaking and they hardly succumb to damage. They are used in aerospace manufacturing because it simplifies both production and maintenance.  Another reason why rivets are used because aluminium materials used are intolerable to heat.

Can you assist me with rivet selection?

Sure, the Aerobolt team can assist with rivet selection and so much more. We are one of Sydney's leading rivet supplier with a comprehensive range of general rivets plus industrial strength structural rivets with a wide range of rivet guns. You can reach out to us by either telephoning us on 02 9755 3747 or email via the contact us page.  

Do you deliver rivets throughout Australia?

Yes, we can deliver Australia wide through our network team of courier companies. In Sydney we offer our customers same day delivery if you order before 10.00am or the next day. Deliveries to regional New South Wales or major Australian cities such as Melbourne, Brisbane including regional South Eastern Australia are either next day delivery or 2 days turnaround.

Do you deliver to New Zealand?

Yes, we deliver worldwide.  

Stainless Steel Rivet  Summary.

The key difference between grade 304 & grade 316 stainless steels is that the 316 has more nickel and a bit of molybdenum in the mix, which makes it a little  more expensive. The increased nickel content and the inclusion of molybdenum allows for grade 316 stainless steel to have better chemical resistance than the 304 stainless steels. Its ability to resist acids, chlorides, including salt, makes grade 316 ideal for numerous chemical, food, and marine applications. Most of the Huck Aerobolt range of fasteners indicate the grade of stainless including rivets, nutserts, rivnuts and so much more. The structural rivets range with more than one grade of stainless includes Magna-Lok, Allok and Orlock rivets.

Rivets offer superior fastening capabilities for both heavy-duty and light fabrication applications. A rivet in one form or another has been used by people for numerous centuries and it is hard to imagine a world without rivets. They are found in the metal roofing and guttering that protect our homes, to the air conditioners that make us more comfortable to the cars we drive, the planes we fly and the ships we sail. Wherever there is a construction site or a fabrication workshop there is bound to be a rivet in use. 

It is evident that rivets are important option in numerous building and manufacturing sectors. Irrespective of the rivet type or stainless steel grade required for your project, be assured with a bit of planning your project will end up as a successful one. Here at Aerobolt we have a comprehensive range of rivet products  and can assist in your application, simply call us on 02 9755 3747 or contact us for all your riveting requirements.