Screws are essential fasteners used across nearly every industry—from construction and manufacturing to electronics, aerospace, and medical devices. While their function may appear simple, choosing the right screw material is critical for ensuring safety, durability, cost-efficiency, and compliance with engineering standards.
Screws can be made from a wide range of materials, including carbon steel, stainless steel, nickel-based alloys, brass, aluminum, titanium, and even plastics. Each type has distinct mechanical properties, corrosion resistance, and suitability for different environments. Whether you’re fastening wood, metal, or composite materials in humid, corrosive, or high-temperature settings, understanding what screws are made of—and how to use them—is the first step toward long-term reliability and performance.
This guide provides a comprehensive overview of screw materials, including their types, advantages, limitations, and typical applications. You’ll also find practical advice on how to select and use screws based on material, common surface treatments, and how to avoid common mistakes like galvanic corrosion or material failure. Whether you’re an engineer, contractor, or procurement specialist, this information will help you make informed, cost-effective, and technically sound fastening decisions.
Understanding What Screws Are Made Of
Knowing what materials screws are made of is the first step toward safe, durable, economical, and compliant use.
1. Ensure Safety and Structural Integrity
- Different screw materials offer varying strength, ductility, and durability. For example:
- Load-bearing screws must have sufficient tensile strength.
- Using brittle materials by mistake may lead to breakage, loosening, and even structural failure.
2. Suitability for Harsh Environments
- Screws are often used in extreme conditions—humidity, chemicals, high temperatures, or freezing climates. Understanding the material helps select screws with:
- Corrosion resistance (e.g., 316 stainless steel for coastal areas);
- High-temperature tolerance (e.g., Inconel for boilers);
- Chemical resistance (e.g., Hastelloy for chemical equipment).
3. Avoid Material Failure or Galvanic Corrosion
- In dissimilar metal combinations (e.g., stainless steel + aluminum), improper screw materials may cause galvanic corrosion or stress corrosion cracking, leading to drastically reduced service life or component failure.
4. Cost-Effectiveness
- Choosing the right material = the best performance at the lowest effective cost.
- Over-specification leads to waste;
- Under-specification causes repairs, rework, or complete failure.
5. Compliance with Industry Standards
- Industries like construction, aerospace, medical, and petrochemical follow strict standards (ASTM, DIN, ISO). Understanding materials helps match specifications and avoid non-compliance.
6. Improve Product Quality and Lifespan
- Proper material selection extends the life of both the screw and the connected component, reduces maintenance frequency, and boosts user satisfaction.
Common Screw Materials by Alloy Type
1 Carbon Steel
The most basic and cost-effective screw material, with high strength. Commonly used in structural work, woodworking, furniture, and general machinery. Requires surface treatments like plating or galvanizing for corrosion resistance.
2 Austenitic Stainless Steels
Grades: 304 / 304L / 316 / 316L / 316Ti / 310S / 321 / 347 / 309 / 317L / 253MA / 314
These steels offer excellent corrosion resistance and formability, used in architecture, food equipment, chemical processing, etc.
304/304L: Most common, general-purpose corrosion resistance.
316/316L/316Ti: Molybdenum-added for better chloride resistance, ideal for marine or chemical environments.
310S / 314 / 253MA: Great oxidation resistance at high temperatures.
3 Precipitation-Hardening Stainless Steels (PH Stainless)
Grades: 17-4PH / 17-7PH
These are strengthened through aging heat treatment and offer excellent strength and corrosion resistance. Common in aerospace, pressure vessels, and precision fasteners.
4 Duplex Stainless Steels
Grades: F51 / F53 / F55 / F60 / F61
Combining austenitic and ferritic structures, duplex stainless steels offer high strength and superior resistance to pitting and stress corrosion. Ideal for desalination plants, offshore platforms, paper mills, and petrochemical systems.
5 Corrosion-Resistant / Super Austenitic Stainless Steels
Grades: 254SMO / 1.4529 / 904L / 318 / AL-6XN / Alloy 31 / Alloy 20 / Alloy 28 / C4 / Nitronic 60 / XM-19
These high-performance materials are ideal for extreme chemical environments with high chloride, acid, or alkali content. Used in reactors, pharmaceutical machinery, and seawater systems.
6 Urea-Grade Stainless Steels
Grades: 724L / 725LN
Specially developed for urea synthesis plants. These offer outstanding ammonia and intergranular corrosion resistance. Commonly used in high-pressure urea towers and condensers in fertilizer factories.
7 Nickel Alloys
Grades: Nickel 200 / 201
Pure nickel offers excellent ductility, alkalinity resistance, and thermal conductivity. Widely used in caustic alkali environments, such as caustic soda concentrators and electrolyzers.
8 Monel Alloys
Grades: Monel 400 / Monel K500
Copper-nickel alloys with excellent corrosion resistance, especially in seawater, brine, and certain acids. Monel K500 also adds high strength, ideal for marine hardware, pumps, and valves.
9 Hastelloy Alloys
Grades: Hastelloy C / C22 / C4 / C276 / C2000 / C59 / X / B / B2 / B3
These are designed for extremely corrosive environments, including strong acids and oxidizers.
C series: for oxidizing conditions
B series: for reducing conditions
Common in chemical towers, acid systems, and exhaust ducts.
10 Inconel Alloys
Grades: Inconel 600 / 601 / 625 / 718 / 725 / X750
Nickel-chromium alloys with excellent high-temperature strength and corrosion resistance. Widely used in aerospace engines, nuclear reactors, and heat treatment furnaces.
11 Incoloy Alloys
Grades: Incoloy 800 / 800H / 800HT / 825 / 926 / 901
Suited for environments with oxidation, carburization, and high-temperature corrosion. Common in heat exchangers, heating elements, and fasteners in acidic systems.
12 High-Temperature Alloys
Grades: GH2132 / GH4145 / GH4169 / Nimonic 80A
These alloys are used in continuous high-temperature operations such as gas turbines, jet engines, and nuclear components. They provide high strength, creep resistance, and oxidation resistance.
These advanced alloys significantly expand the use of screws in extreme environments (high temperature, pressure, and corrosion). Material selection should be based on working conditions (temperature, medium, stress) and cost-effectiveness.
Besides the high-performance alloys and stainless steels mentioned earlier, common screw materials also include the following categories, which are widely used in everyday engineering, construction, electronics, furniture, and other fields.
13 Low Carbon Steel
- Features: Low cost, easy to machine, moderate strength.
- Applications: Widely used in non-load-bearing structures, furniture, household appliances, etc.
- Drawbacks: Poor corrosion resistance—usually requires surface treatments such as galvanizing, nickel plating, or phosphating.
14 Medium Carbon Steel / Alloy Structural Steel
- Features: Higher strength and hardness than low carbon steel, can be heat-treated for improved performance.
- Applications: Suitable for machinery, structural components, and parts requiring higher strength.
- Common Grades: 35#, 45#, 40Cr, 20MnTiB, etc.
15 Tool Steel
- Features: Very high hardness, wear resistance, and strength—used for cutting tools and molds.
- Applications: Specialty fasteners like mold screws, precision locating screws.
- Representative Grades: Cr12MoV, H13, T8, T10, etc.
16 Copper and Copper Alloys (Brass / Bronze)
- Features: Excellent electrical conductivity, corrosion resistance, and decorative appearance.
- Applications: Electrical equipment, precision instruments, furniture hardware.
- Common Types: Brass, tin bronze, phosphor bronze.
17 Aluminum and Aluminum Alloys
- Features: Lightweight, corrosion-resistant, easy to form.
- Applications: Ideal for lightweight designs in aerospace, electronics, building façades.
- Note: Lower strength—best for non-load-bearing uses.
18 Titanium and Titanium Alloys
- Features: Lightweight, high strength, corrosion-resistant, non-magnetic.
- Applications: Aerospace, medical implants, deep-sea equipment.
- Common Grades: TA2 (pure titanium), TC4 (Ti-6Al-4V alloy).
19 Plastic Screws
- Features: Insulating, corrosion-resistant, lightweight, cost-effective.
- Applications: Electronics, lab equipment, non-load-bearing assemblies.
- Common Materials: Nylon, polycarbonate (PC), polypropylene (PP), POM, PEEK, etc.
How to Use Screws Based On Their Material ?
1. Understand the Application Environment: Different environments require different bolt materials:
| Environment Condition | Recommended Bolt Material |
| Indoor dry environment | Low-carbon steel, standard stainless steel (e.g., 304) |
| Outdoor, humid or rainy | Stainless steel 316, hot-dip galvanized steel |
| High-temperature (>600°C) | Inconel, 310S, 253MA |
| Strong acid/alkali exposure | Hastelloy, Titanium, 904L, Alloy 20, etc. |
| Marine or salt fog environment | Duplex stainless (F55, F53), Monel, 316Ti |
| Food/medical applications | 304L, 316L, Titanium, PEEK |
| Heavy mechanical load | Alloy steel (e.g., Grade 10.9/12.9), 17-4PH, 40Cr |
2. Confirm Mechanical Strength Requirements: Bolts are classified into different strength grades depending on their material and heat treatment (especially carbon/alloy steel):
| Strength Grade | Typical Material | Common Applications |
| 4.8 / 5.6 | Mild carbon steel | Furniture, light structures |
| 8.8 | Alloy structural steel | General machinery, construction |
| 10.9 | Medium-carbon alloy | Heavy machinery, automotive |
| 12.9 | High-strength alloy | Pressure flanges, engine components |
Note: High-strength bolts have excellent load capacity but usually lower corrosion resistance, so coatings are often required.
3. Avoid Galvanic Corrosion Between Dissimilar Metals: When bolts contact dissimilar metals—especially in conductive or wet environments—galvanic corrosion may occur:
| Risky Combination | Recommended Solution |
| Stainless bolt + Aluminum structure | Use insulating washers or select aluminum/titanium bolts |
| Carbon steel bolt + galvanized steel | Acceptable but check for small potential differences |
| Stainless steel + Copper/brass | Avoid direct contact or isolate with plastic washers |
4. Consider Heat Treatment and Machinability: Some materials require heat treatment (e.g., precipitation hardening, quenching) to reach their intended performance:
- High-strength bolts: Confirm heat treatment status before use.
- Austenitic stainless (304/316): Not heat-treatable for strength, strengthened by cold working.
- Titanium bolts: Require careful machining to avoid stress concentration.
5. Choose Suitable Surface Treatment or Coating: Material and environmental conditions determine appropriate surface treatments:
| Material | Surface Treatments | Purpose |
| Carbon steel | Zinc plating, hot-dip galvanizing, Dacromet, phosphating | Improve corrosion resistance |
| Alloy steel | Black oxide, nickel plating, fluorocarbon coating | Corrosion protection & aesthetics |
| Stainless steel | Polishing, electropolishing, passivation | Enhance protective oxide layer |
| Copper alloys | Usually no treatment needed | Optional nickel plating for looks |
| Plastics | No treatment needed | UV protection if outdoors |
6. Comply with Relevant Industry Standards: Specific industries like aerospace, petrochemicals, and healthcare require certified materials:
- ASTM / ASME / ISO / DIN certifications
- NACE (for oil and gas corrosion resistance)
- PED (Pressure Equipment Directive)
- FDA (Food contact safety compliance)
FAQ: What Are Screws Made Of & How to Use Them
It may lead to:
- Corrosion or rust
- Bolt failure or breakage
- Galvanic corrosion with other metals
- Reduced structural integrity
- Non-compliance with regulations
Use similar or compatible metals together. If using dissimilar metals (e.g., stainless steel screw with aluminum part):
- Add insulating washers or bushings
- Use coated screws or non-conductive barriers
It depends on:
- The material (stainless or titanium is better for reuse)
- The application (structural bolts are often one-time use)
- Whether the threads are damaged or deformed
Always inspect before reuse.
Contact MT.BOLTS
MT.BOLTS specializes in the manufacturing and supply of Steel Fasteners, including screws, bolts, nuts, and washers. Our products conform to international standards (ANSI / ASTM / DIN / ISO / JIS) and are available in various materials, dimensions, and surface finishes.
Contact us today to learn more about fasteners and to procure high-quality products. Our technical team is ready to provide expert support and custom selection solutions.
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