What Are Galvanized Screws and Why Choose Them for Your Projects?


What Are Galvanized Screws and Why Choose Them for Your Projects?

When it comes to choosing the right fasteners for your projects, it’s essential to consider factors like durability, corrosion resistance, and overall performance. Galvanized screws have become a popular choice among DIY enthusiasts and professionals alike due to their ability to withstand harsh environments and provide long-lasting protection against rust and corrosion.

In this article, we’ll dive into the world of galvanized screws, exploring what they are, how they’re made, and the key benefits they offer. We’ll also compare galvanized screws to other common fastener options, such as plain steel and stainless steel screws, to help you make an informed decision for your specific needs.

What are Galvanized Screws

Galvanized screws are essentially steel fasteners that have been treated with a zinc coating to prevent corrosion. The process of adding this protective layer is known as galvanization. Galvanized screws are commonly used in construction for securing drywall, outdoor projects, fencing, gutters, poles, agricultural equipment, and attaching metal roofing which are generally cheaper than stainless steel screws while still providing good corrosion resistance, making them an economical choice for many applications.

Types of Galvanized Screws

Galvanized screws can be categorized based on the method used to apply the zinc coating:

  1. Hot-dip galvanized screws: These screws undergo the hot-dip galvanizing process, where they are dipped in a bath of molten zinc, resulting in a thicker and more durable coating.
  2. Zinc-plated screws (also known as electro-galvanized screws): These screws receive a thinner zinc coating through electroplating, which involves using an electrical current to deposit zinc onto the screw surface.

Both types of screws are considered galvanized because they have a zinc coating that protects the steel from corrosion.

However, they differ in terms of the application process, coating thickness, appearance, and corrosion resistance. Hot-dip galvanized screws have a dull, mottled gray appearance, while zinc-plated screws are shinier and smoother.

The Size and Length of Galvanized Screws

Screw Size (Gauge)Diameter (mm)Available Lengths (Inches)Available Lengths (mm)
#22.181/2″, 5/8″, 3/4″12.7, 15.88, 19.05
#63.511/2″, 5/8″, 3/4″, 1″12.7, 15.88, 19.05, 25.4
#84.171/2″, 5/8″, 3/4″, 1″, 1-1/4″, 1-1/2″, 2″12.7, 15.88, 19.05, 25.4, 31.75, 38.1, 50.8
#104.831″, 1-1/4″, 1-1/2″, 2″, 2-1/2″, 3″25.4, 31.75, 38.1, 50.8, 63.5, 76.2
#125.491-1/2″, 2″, 2-1/2″, 3″38.1, 50.8, 63.5, 76.2
1/4″6.351-1/2″, 2″, 2-1/2″, 3″38.1, 50.8, 63.5, 76.2

*Please note that not all lengths may be available for every screw size, and some manufacturers might offer additional or intermediate sizes and lengths not listed here. It’s always best to check with the specific supplier or manufacturer for their exact product offerings. If you have any inquiries, please contact us, and we will provide exceptional solutions for you.

How Galvanized Screws are made? Detailed Explanation 

How Galvanized Screws are made? Detailed Explanation

Hot Dip Galvanizing Process:

  1. Cleaning and preparation: The steel screws are first cleaned to remove any dirt, oil, or rust. This typically involves a caustic soda solution to remove organic material, followed by an acid bath (usually hydrochloric or sulfuric acid) to remove surface oxides
  2. Fluxing: The screws are then dipped in a flux solution, usually zinc ammonium chloride, which helps the molten zinc adhere to the steel surface
  3. Galvanizing: The screws are immersed in a bath of molten zinc at a temperature of around 840-860°F (450-460°C). The zinc metallurgically bonds to the steel, forming a series of zinc-iron alloy layers. The screws remain in the bath until the reaction is complete
  4. Removal and cooling: The screws are removed from the zinc bath, and excess zinc is removed by spinning the parts in a centrifuge or brushing. The zinc coating is then allowed to cool and solidify

Zinc plating (electro-galvanizing)

  1. Cleaning: The steel screws are first cleaned thoroughly to remove any dirt, oil, grease, or contaminants from the surface. This is typically done using alkaline cleaners, solvents, or acid pickling to ensure a clean, oxide-free surface for optimal zinc adhesion.
  2. Electroplating: The screws are then placed into an electrolytic cell containing a zinc solution (usually zinc sulfate or zinc chloride) and subjected to an electric current. The screws act as the cathode (negatively charged), while a zinc anode (positively charged) is used. The electric current causes the positively charged zinc ions to migrate and deposit onto the surface of the screws, forming a thin, uniform layer of zinc.
  3. Rinsing and drying: After electroplating, the screws are rinsed with water to remove any excess plating solution and then dried, often using hot air or centrifugal dryers.
  4. Chromate conversion (optional): For added corrosion protection and a decorative finish, the zinc-plated screws may undergo a chromate conversion process. This involves dipping the screws in a chromate solution, which forms a thin, protective chromate layer on top of the zinc coating.

Mechanical Galvanizing Process:

  1. The screws are placed in a large rotary barrel along with zinc powder, glass beads, and chemical promoters
  2. As the barrel rotates, the glass beads blast the screw surfaces with zinc particles, causing the zinc to mechanically bond to the steel
  3. This process is done at room temperature, which minimizes the risk of hydrogen embrittlement and ensures the mechanical properties of high-strength screws are maintained

Compare Galvanized Screws with Other Fasteners

Compare Galvanized Screws with Other Fasteners

In your quest to choose the right fasteners for your projects, understanding how galvanized screws stack up against steel and stainless steel screws is crucial. You’ll discover key differences in terms of cost, durability, and suitability for different environments.

Fastener TypeCorrosion ResistanceCostSuitability
Plain Steel ScrewsLow – prone to rust and corrosionLowestIndoor or dry environments
Galvanized ScrewsGood – zinc coating provides protection, but can corrode if damagedSlightly higher than plain steelOutdoor projects with some exposure to elements
Stainless Steel ScrewsExcellent – especially in moist or chemical environmentsHighest, but justified by longevityMarine environments or applications demanding high corrosion resistance

In conclusion, plain steel screws are the cheapest but offer the least corrosion resistance, making them suitable mainly for indoor, dry environments.

Galvanized screws provide good rust protection due to their galvanized steel coating at a slightly higher cost than plain steel. They are ideal for general outdoor use where severe corrosion isn’t a major threat.

Stainless steel screws offer the best corrosion resistance, particularly in harsh environments like marine applications. While they have the highest cost, their longevity can justify the investment in the right circumstances.

Applications, Maintenance and Lifespan of Galvanized Screws

Practical Applications

1. Outdoor Projects

You’ll find that galvanized screws are an asset in outdoor settings due to their corrosion resistance. The perfect threaded solution is Ideal for:

  • Fencing: Secures wooden panels while resisting the elements.
  • Outdoor furniture: Maintains integrity even with fluctuations in weather.

2. Construction Projects

For larger-scale endeavors, the affordability and resilience of galvanized screws make them a staple. They are well-suited for:

  • Structural frames: Ensures stability with a protective zinc coating.
  • General construction: Suitable for various components, providing longevity and reducing maintenance.

3. Woodwork and Decking

When you’re working withtreated lumber or embarking on a decking project, galvanized screws are the go-to for their compatibility and the protective layer they offer. They help prevent:

  • Cosmetic issues: Minimized with special types designed for composite materials.
  • Degradation: The galvanized layer combats the effects of outdoor exposure.

How to Maintain Galvanized Screws

When you’re dealing with galvanized screws, the key to their longevity is the protective barrier that galvanization provides. This zinc coating shields the steel withstand moisture and oxygen, both of which can lead to oxidation and rusting. Think of it as an armor that keeps your screws tough against the onslaught of the elements.

For Routine Maintenance:

  • Check for scratches or damage on the coating periodically, as this could expose the steel.
  • If you notice any damage, a touch-up with a zinc-rich paint can help maintain the integrity of the coating.
  • While regular cleaning isn’t necessary, it’s a good idea to keep the screws free from excessive dirt and grime which could retain moisture.

Anticipated Lifespan:

EnvironmentExpected Lifespan
Rural80+ years
Suburban60+ years
Temperate Marine55+ years
Tropical Marine50+ years

These estimates assume a minimum zinc coating thickness of 2.5 mils.

Harsher environments or constant exposure to corrosive materials can shorten this lifespan. Galvanized screws boast good corrosion resistance, but not as much as their stainless steel counterparts.

If your project will face high salinity or industrial chemicals, opting for stainless steel might be prudent.

Frequently Asked Questions

How are galvanized screws different from stainless steel screws?

Galvanized screws are coated with zinc to prevent corrosion, whereas stainless steel screws are made from an alloy that inherently resists rust and corrosion. Galvanized screws are typically less expensive but may not match the strength and corrosion resistance offered by stainless steel.

Are galvanized screws resistant to rust?

Galvanized screws resist rust due to their zinc coating, which acts as a barrier against moisture and oxidation. However, the level of rust resistance depends on the thickness of the zinc layer and environmental conditions.

How can you identify a galvanized screw?

You can identify a galvanized screw by its distinctive appearance; it usually has a matte gray finish, slightly rough texture, and may show some crystallization patterns known as “spangle.”