Rivet materials 

In this guide, we’re focusing on metal rivets and the different materials available. But first, we’ll walk you through what rivets are, their advantages and disadvantages and finally, which metals are compatible and which aren’t. Specifically, we’ll cover:

What are rivets?
How do rivets work?
Advantages of rivets?
Disadvantages of rivets
Materials used for rivets
What materials can work together?

 

What are rivets?

 

A rivet is a cost-effective and straight-forward mechanical fastener used to join a variety of materials, such as metals, plastics and composites. If that sounds like the job of screws, it is, but rivets make more sense to use in certain circumstances. For example, you’ll want a rivet if you’re joining materials that are too thin or brittle for a screw. Also, rivets don’t require threads in the materials you’re joining, where screws do. 

These fasteners are ideal for supporting shear and tensile loads, and applications involving complicated or limited access. Rivet styles vary, as do the different types of rivets available.
 

Advantages of rivets

What are rivets used for? Anything requiring a permanent fixing. All rivet types are very similar to nuts and bolts, except that nuts are screwed in and can easily be unscrewed for disassembly and reassembly. If you want a permanent joint, then quality rivets have the advantage, as they have to be damaged or even broken to be removed. 

Rivet fasteners can also secure joints with short clamp length, and they don't loosen when exposed to vibration. This is why aircraft rivets, such as blind rivets, are used. When vibration is present, only rivets will do. 

How does welding compare to riveting metal? Riveted sheet metal is still more reliable when subjected to vibrations and impact forces. Riveted metal panels are also free from thermal after-effects, as no heat is required to form the joint as used with welding. 

Disadvantages of rivets

The clamping force of rivets is inconsistent, so it’s best to consider bearing capacity. 

Riveting is more time intensive than welding, as it requires laying out and drilling holes. Thus, the labour cost of riveting is higher. Stress concentration causes another concern. The holes in sheet metal with rivets can weaken the plate’s working cross section. This can be addressed with additional thickness and overlapping plates, but you’re looking at using more metal. Also, the strap plate and rivets add more weight compared to a welded joint. 

Of course, these are advantages and disadvantages of using heavy-duty rivets for structural applications. Lightweight rivets are available, even in metal, such as hollow rivets, which have an empty core, used for electronic applications. 

With so many types of rivets, you have a lot to choose from – but you’ll still need to weigh the advantages and the disadvantages to decide if riveting is the right avenue to take.
 

What materials are used for rivets?

Rivet material is critical and affects the strength, corrosion resistance and overall performance of the riveted joint. Your application will determine the material you should use. For example, riveting steel requires that you think about the strength of the rivet material. must be able to withstand the loads and forces that the joint will be subjected to. For example, steel rivets are stronger than aluminium rivets, but aluminium rivets (and stainless-steel solid rivets) are more corrosion resistant. 

Your rivets should have the same mechanical properties as the components you’re joining. Which metal rivets for steel make the most sense? Can you use aluminium rivets on steel? The short answer is no. Alumunium rivets in steel will cause corrosion to set in and destroy the rivets, leading to failure in the fastener. Likewise, it’s the same reason you can’t use steel rivets in alumunium. 

Preventing galvanic corrosion means choosing metals that are close together in the galvanic series. By selecting compatible metal materials, you reduce the risk of corrosion. Copper rivets for metal? Avoid aluminium sheets and look at stainless steel, brass or copper. 

Plastic rivets, of course, resist corrosion, so you don’t have these issues. Plastics are ideal as rivets for soft materials, from nylons to low density polyethylene. 

However, everything we’ve written thus far doesn’t tell you what the material is providing, so here’s a look at different rivet materials:

Aluminium

With added magnesium, aluminium is lightweight, corrosion resistant when used with a compatible material, and durable. Pure aluminium rivets are not strong enough for structural components, and will require the addition of alloying elements if used for that purpose. 

Most rivets used in aircraft construction have an aluminium base. A countersunk head is ideal for this application, as the lack of protrusions above external surfaces eliminate aerodynamic drag. For this reason, aluminium countersunk rivets, or flush rivets as they’re sometimes called, are also used in the automotive industry. It's also a popular material for HVACs that use rivets, whether using a dome shaped head or flush rivet. 

Brass

Malleable with high strength and low friction, brass rivets for metal do not create sparks, as welding does. For this reason, brass rivets are ideal for making a gas-tight joint, which is why the typical application is gas appliances.

Copper

Copper is ductile and offers high strength and decorative appeal. As an excellent conductor of electricity and heat, copper rivets for metal are well suited for electrical appliances.

Copper nickel

Often, these rivets are 80% copper and 20% nickel, which gives these fasteners high resistance to corrosion, stress corrosion and high temperatures. For these reasons, copper-nickel rivets are commonly used in ship manufacturing and appliances that operate in corrosive environments.

Steel

Good tensile strength, hard, durable and withstands wear, high-carbon steel rivets require more material while their moldability decreases. Low-carbon steel does a better job at fitting well in its application. While it’s weaker due to its lower carbon content, it still has good tensile strength. Both steels are used in aircraft, automotive and rail transport, while low-carbon steel rivets are also found in the construction and furniture industries. Both work well as structural steel rivets. 

Steel blind rivets – also known as pop rivets – with waterproof seals are popular in the oil & gas industry for their durability. 

Stainless steel

Strong, hard, withstands wear with very good corrosion resistance. Stainless steel rivets have good hygienic characteristics, strength-to-weight advantage and good impact resistance. Stainless steel rivets are used in aircraft, automotive and rail transport.

Plastic

Plastic rivets can be used to join non-plastic materials, such as sheet metals, rubber, urethane and other softer materials. You’ll find plastic rivets in consumer appliances
Electronics, construction and furniture. 

You can learn more in How to choose your plastic rivets: a guide. 

What materials can work together?

Choosing rivets for metal requires careful consideration, unless you’re going with plastics. 
When dissimilar metals come into contact within a corrosive environment, a galvanic action occurs which corrodes one metal at a faster rate than the other.

The rate of corrosion depends upon several factors:
●    Electric -- the difference in electrical potential
●    The conductivity of the electrolyte
●    The relative sizes of the contacting areas

This means that in applications high in moisture content, such as air conditioners, special care must be taken to lessen the effect of galvanic corrosion. To help you choose your metal rivet, here are the metals which should be used together and just as importantly, those that shouldn’t.

Rivet material selection

Rivet shell material	Metals being joined
		Aluminium	Al/Zn- coated steel	Zinc-coated steel	Stainless steel	Copper	Brass
Aluminium		Yes	Yes	–	No	No	No
Steel, zinc-plated		No	Yes	Yes	No	No	No
Stainless steel		–	–	–	Yes	Yes	Yes
Copper Nickel		No	No	No	Yes	Yes	Yes
Copper		No	No	No	Yes	Yes	Yes

Yes: Compatible
No: Incompatible
– : Compatible in mild environments, though some corrosion may occur. Paint both metals to reduce reaction.

 

Rivet coatings

Before installing rivets, you’ve thought about your metals and how they work together. If the sheet-metal rivets that you want aren’t as close on the galvanic scale as you’d like, consider coatings.

Coatings are often used for aesthetic purposes and also to add corrosion resistance. Zinc is a common coating for steel rivets. An Almac® coating combines aluminium and zinc for corrosion resistance and works particularly well with aluminium rivets and materials. Copper rivets with coated carbon steel add strength.

The point is, you can add more properties to your choice of rivet material and get the best possible solution for your application.
 

 

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