5 of the Top-Performing Corrosion-Resistant Materials

Originally published on fastradius.com on September 9, 2020

How to Choose the Right Corrosion-Resistant Material

Material selection is a crucial part of any manufacturing process. Choosing the right material is so important because the material defines the chemical and mechanical properties of the component being manufactured, can significantly influence the longevity of the component, and ensures that part functions properly. Corrosion-resistant materials play a significant role in manufacturing because of their material properties and their lack of reactivity to harsh environmental conditions and chemicals.

For example, many aerospace components are manufactured using titanium, tungsten, and carbon fiber because these materials are very strong, yet lightweight and flexible. Unfortunately, these materials can react with one another and cause galvanic corrosion over time, localized corrosion where there’s an exchange of ions between materials. Here, corrosion-resistant materials preserve the integrity of parts in one of the most strictly regulated industries in the world.

From an environmental perspective, pollution-free solar and wind energy sources are vulnerable to harsh conditions and corrosion-resistant materials help protect their critical components from damage over time. This helps manufacturers safely build components for alternative energy sources and contribute to a more sustainable economy. For engineers looking to protect their parts from corrosive mediums like acids and salts, or UV degradation, here are the best corrosion-resistant materials to consider.

Examples of Corrosion-Resistant Materials

1. Stainless Steel

Stainless steel alloys are renowned for the corrosion-resistance, ductility, and high strength. Corrosion resistant qualities in stainless steels are directly tied to their chromium and nickel content — more of these elements correlate with increased resistance.

Most stainless steel alloys on the market today contain at least 18% chromium. When chromium oxidizes it forms a protective layer of chromium oxide on the surface of the metal part, which both prevents corrosion and prevents oxygen from reaching the underlying steel.

*Stainless steel has a wide variety of applications, from kitchen appliances like pots and pans to car parts to surgical implants.*

Since this material has a high melting point and can sustain and support high pressure, it’s also well-suited for construction, machine building, and manufacturing storage containers. 304, 430, and 316 stainless steel are the most commonly specified grades of stainless steel, with 316 being the grade of choice for harsh marine environments.

However, stainless steel’s durability and high corrosion-resistance come at a high price point, making them prohibitively expensive for some manufacturers. Also, stainless steel alloys can be difficult to work with, particularly in welding, because of their high melting point.

2. Aluminum

Aluminum alloys are non-toxic, 100% recyclable, have a high strength-to-weight ratio, have high thermal and electrical conductivity, and are easily machinable. Also, aluminum is unique because it’s one of the few materials that are naturally corrosion-resistant.

This material contains little to no iron so it cannot rust, though it can oxidize. When an aluminum alloy is exposed to water and oxidizes, a process called self-passivation, a film of aluminum oxide forms on the surface of the part and protects it from corrosion. Aluminum 5052-H32 is more corrosion-resistant than other varieties of aluminum and forms a bright, smooth finish.

This oxidation process can also be closely controlled through a process called anodization. Also, aluminum is unique because it’s one of the few innovative materials for additive manufacturing that are naturally corrosion-resistant. Anodization is a low-cost controlled finish that is widely used. This process also allows for color to be added to the part, allowing further customization for different use cases.

Aluminum is frequently used in aerospace applications, automotive body panels, salt-water sensitive applications, and other situations where a high-performance material is required. Manufacturers should consider using aluminum if they need an affordable corrosion-resistant material, while keeping in mind that aluminum fabrication can be messy and a hassle to work with.

3. Soft Metals

Soft metals, or red metals, include corrosion-resistant materials like copper and its alloys, brass and bronze. Copper is malleable, ductile, and an excellent conductor of heat and electricity. These metals can ensure corrosion resistance throughout the life cycle of a given component. . Copper won’t corrode over time; when it oxidizes, it forms a green outer layer called patina, which protects the part from further corrosion.

Copper is often the corrosion-resistant material of choice for manufacturers in the semiconductor industry, and it’s most commonly found in wires and cables. It’s used to make circuit boards, electromagnets, heat exchangers, and electrical motors.

Copper also plays a key role in manufacturing parts for renewable energy systems. Since copper is such an excellent thermal and electrical conductor, systems powered by copper transmit energy more efficiently and with a lesser environmental impact.

4. Polypropylene

Metals aren’t the only corrosion-resistant materials available. Polypropylene, one of the most popular plastics in the manufacturing industry and is an especially common plastic for producing car parts. It’s also one of the most corrosion-resistant plastics.

This thermoplastic polymer resin has been nicknamed the “steel of the plastic industry” for its toughness, ability to withstand high levels of physical pressure, and resistance to a wide range of corrosive elements such as oil, solvents, water, bacteria, and more. High-density polypropylene (HDPE) offers higher tensile strength and an increased working temperature range.

*Polypropylene can be found in almost anything — ropes, carpeting, car batteries, reusable containers, activewear, lab equipment, and more.*

However, this material’s high flammability and high thermal coefficient limit its usefulness for high-temperature applications. Also, it’s important to note that polypropylene is susceptible to oxidation, UV degradation, and certain chlorinated solvents.

5. Polytetrafluoroethylene (PTFE)

PTFE, commonly referred to by its brand name Teflon, is a chemical- and corrosion-resistant engineering thermoplastic with the lowest friction coefficient of any known solid material. PTFE is hydrophobic, meaning it won’t absorb water, and has good electrical insulating power in both hot and wet environments.

PTFE is best-known for its commercial and medical applications — creating non-stick coatings for pots and pans and providing an anti-friction coating for medical and industrial applications. Thanks to its low friction, this material is used to manufacture bearings, gears, slide plates, seals, and other small parts that are critical to industrial applications. PTFE is also frequently used in carbon fiber and fiberglass composites.

Still, PTFE does have its limitations. This material is hard to join and it’s sensitive to creep, abrasion, and radiation. Also, fumes released by PTFE can be toxic in closed environments. It’s best to consult an experienced manufacturing partner before making any major decisions about materials.

Get Expert Advice on Material Selection

Corrosion-resistance is an extremely desirable trait, especially in the semiconductor, power, aerospace, and automotive industries. There is a wide range of corrosion-resistant materials to choose from, including the aforementioned five, and product teams must do their due diligence during material selection to ensure they’re fulfilling their unique project requirements.

An experienced digital manufacturing partner, like SyBridge, can help product teams answer the toughest questions throughout the product development process. Should you use metal or plastic? Is polypropylene just as good as stainless steel? Our team has years of experience navigating all things additive and traditional manufacturing, and we’ll help each customer choose the corrosion-resistant material that will protect their parts for the long-term. Contact us today to get started.

Polyoxymethylene (POM), more commonly known as acetal or its branded name Delrin®, is an engineering plastic offering low friction, high stiffness, and excellent dimensional stability. Polyoxymethylene is a category of thermoplastics and includes many different formulations of the material, all of which vary slightly. As such, it’s important to learn as much as you can about each type before choosing one for your next project. Delrin® is a semi-crystalline engineering-grade thermoplastic widely used to create highly precise parts. In general, Delrin® provides impressive dimensional stability and sliding properties. It’s known for its high strength, wide operating temperature range (-40°C to 120°C), and excellent mechanical properties. Here’s everything you need to know about this material, from how it’s made to its best-fit applications. Inside the polyoxymethylene production process Acetal was first discovered by German chemist Hermann Staudinger in 1920 before it was commercially synthesized by research chemists at DuPont, the original manufacturers of Delrin® plastic, in 1956. Like all other plastics, acetal is created by distilling hydrocarbon fuels down into lighter groups called “fractions,” which can then be combined with other catalysts via polymerization or polycondensation to produce a finished plastic. To make an acetal homopolymer like Delrin®, anhydrous formaldehyde must be generated by causing a reaction between aqueous formaldehyde and alcohol to form a hemiformal. The hemiformal is then heated to release the formaldehyde, and the formaldehyde is polymerized by anionic catalysis. The resulting polymer is stabilized when it reacts with acetic anhydride, which creates polyoxymethylene homopolymer. Acetal comes in many different commercial varieties and formulations, each with its own advantages and disadvantages. For example, Delrin® 500 is medium-viscosity, all-purpose polyoxymethylene that has a good balance of flow and physical properties. It can be used to produce parts via CNC machining and injection molding and is frequently used to manufacture mechanical parts, fuel systems, and fasteners. Delrin® 1700P, on the other hand, is a very low- viscosity, fast-molding resin that is best suited for parts with complex shapes, thin walls, long flow paths, or multi-cavity tools. It also offers the best molding thermal stability for deposit-free molding in demanding conditions. Since there are dozens of different formulations of acetal, it’s important to do your research and make sure your prospective plastic offers all of the properties you need for your application. Delrin® plastic properties and mechanical specifications small black Delrin pieces Delrin® can also be found in all-purpose industrial equipment like bearings, gears, pumps, and meters. Acetal’s excellent mechanical properties make it extremely versatile, offering a unique blend of properties that you won’t find in most metals or other plastics. Delrin® plastic is strong, rigid, and resistant to impact, creep, abrasion, friction, and fatigue. It’s also well known for its excellent dimensional stability during high-precision machining. Acetal can also stand up to moisture, gasoline, solvents, and a wide range of other neutral chemicals at room temperature. From a design standpoint, parts made with extruded POM naturally have a glossy surface finish. Since acetal is compatible with CNC machining, injection molding, extrusion, compression molding, rotational casting, and more, product teams are free to choose the manufacturing process that works best for their budget and their needs. However, it’s worth noting that Delrin® plastic is typically very challenging to bond. Acetal material properties vary by formulation, but the mechanical properties for Delrin® 100 NC010, one of the most popular formulations, include: Tensile modulus: 2900 MPa Yield stress: 71 MPa Yield strain: 26% Density: 1420 kg/m3 Charpy notched impact strength, +23°C: 15 kJ/m2 Coefficient of linear thermal expansion, normal: 110 E-6/K Water absorption: 0.9% Delrin® does have a few limitations. For instance, even though Delrin® is resistant to many chemicals and solvents, it’s not very resistant to strong acids, oxidizing agents, or UV radiation. Prolonged exposure to radiation can warp the color and cause the part to lose its strength. Also, this material isn’t readily available in a flame-retardant grade, which limits its utility for certain high-temperature applications. Why choose Delrin® plastic? These limitations notwithstanding, there are many reasons to choose acetal over other materials. When compared to other plastics, acetal offers better creep, impact, and chemical resistance, better dimensional stability, and higher strength. It also has a lower coefficient of friction. Acetal outpaces certain metals as well. Parts built with this material have a higher strength-to-weight ratio, better corrosion resistance, and offer more opportunities for part consolidation. You can build thinner and lighter parts faster and at a lower price point with acetal than with a comparable metal. Delrin® plastic can be found in almost every major manufacturing sector. In the automotive industry, common applications include heavy load-bearing gears, fuel system components, loudspeaker grilles, and safety system components like seatbelt hardware. Delrin® can also be found in all-purpose industrial equipment like bearings, gears, pumps, and meters. In the consumer goods and appliances space, this material can be used to make anything from zippers and pens to knife handles and lawn sprinklers. Getting started with Delrin® There’s a lot for product teams to love about Delrin®. It’s strong, stable, versatile, and its excellent mechanical properties make it a good choice for a wide variety of applications in a number of industries. However, with dozens of different formulations of acetal on the market, it can be very challenging to determine which one might be the best fit for your unique project. A seasoned manufacturing partner can help demystify the material selection process. When you partner with Fast Radius, you partner with a team of on-demand manufacturing experts who have years of experience helping product teams navigate material selection. We’re well-versed in the wide range of materials that can be used for both traditional and additive manufacturing — including Delrin®. Once you’ve selected the Delrin® formulation that’s the right fit for your application, our team of experts can help facilitate the entire manufacturing process — from design and prototyping to production and fulfillment. With a full suite of manufacturing services including CNC machining and injection molding, Fast Radius can bring your vision to life quickly and easily. Contact us today to get started.

5 of the Top-Performing Corrosion-Resistant Materials

How to Choose the Right Corrosion-Resistant Material