Waterproofing joints is an important consideration when fabricating metal projects that will be exposed to rain, submerged underwater or assembled near water. To keep water and air out, a breathable, water-resistant sealant is used to fill gaps while still allowing for expansion and contraction.
Silicone is one of the most frequently used sealants to achieve a waterproof, protective joint seal. The flexible, rubbery plastic has high heat resistance and low toxicity, making an ideal sealant choice for plumbing pipes, aquariums, ships and other metal fabrication projects that require a watertight seal.
But how long does it actually last?
Silicone is a synthetic polymer made up of silicon, oxygen and hydrogen or carbon. Synthetic is the keyword here, as silicone is an inorganic substance that will not deteriorate, at least not as quickly as other sealants like polyurethane.
This is especially important, as keeping a metal fabrication project watertight is critical for the long term.
Most metal structures rely on silicone joint sealants for protection from the negative impacts of moisture and water. You’ll find it on everything from architectural railing to industrial enclosures to marine fabrications.
So how long will silicone sealant stay watertight?
Typically around 20 years, depending on factors such as temperature, UV light, exposure and chemical properties of the metal.
Silicone’s high heat resistance is better suited than polyurethane for extreme temperature changes, which can cause joints to expand and contract, and silicone’s flexibility allows for movement as the joints expand and contract.
That said, no sealant lasts forever. Over time, even the best silicone can degrade—especially if it’s exposed to constant UV radiation, harsh chemicals or extreme temperature swings.
We’ve seen silicone fail in as little as 5–7 years on projects where the wrong type was specified or where surface prep was skipped.
Several factors determine how long silicone will perform:
When properly applied, silicone is a multipurpose adhesive and sealant that creates a waterproof, protective seal and can last up to 20 years.
Here’s what we’ve learned from years of sealing metal fabrication projects:
We see silicone used on everything from welded assemblies to architectural panel systems. When it’s done right, it’s one of the most reliable ways to keep water where it belongs—outside your project.
Wondering if silicone is the right solution for your metal fabrication project? At All Metals Fabrication, we’ve been sealing, waterproofing and protecting metal assemblies for years. We can help you choose the right materials and methods for long-lasting results. Contact us today for a free quote.
Silicone typically “skins over” (forms a dry surface layer) within 30 minutes to 2 hours, depending on humidity and temperature. However, this doesn’t mean it’s fully cured. Most silicone sealants require 24 to 48 hours to cure completely throughout their entire thickness.
Higher humidity can actually speed up curing, while cold temperatures slow it down. For best results, don’t expose the sealant to water or stress until it’s fully cured.
Yes, silicone sealant is watertight when properly applied and maintained. Its flexible, rubbery structure creates a barrier that prevents water penetration while still allowing for expansion and contraction of the joint.
However, silicone isn’t indestructible—it can degrade over time from UV exposure, extreme temperatures or chemical contact. Proper surface preparation and choosing the right silicone formulation for your application are critical to achieving a lasting watertight seal.
Most silicone sealants become surface-watertight within a few hours of application, once they’ve skinned over. But for full waterproof performance, you should wait 24 to 48 hours before exposing the joint to water or other elements.
This allows the silicone to cure all the way through, creating a complete molecular bond. Rushing this process can compromise the seal and lead to early failure.
difference between silicone sealant and caulk?
Silicone sealant and caulk serve similar purposes but have different properties. Silicone is more flexible, more durable and more weather-resistant than most caulks, making it better for applications exposed to temperature extremes or constant movement. It also adheres well to metal, glass and many plastics.
Traditional caulk (often acrylic or latex-based) is less expensive and easier to paint, but it’s not as durable and can crack or shrink over time, especially in outdoor applications.
In metal fabrication, silicone is commonly used to seal joints, gaps and seams in assemblies that need waterproofing or air-tightness. This includes architectural metal panels, welded enclosures, marine applications, HVAC ductwork and any project where metal components meet and need protection from moisture, dust or air infiltration.
We also use it for sealing around fasteners and creating weatherproof connections in outdoor installations.
Silicone adheres well to most metals including steel, stainless steel, aluminum and galvanized surfaces. That said, some metals require special consideration.
Copper, brass and certain alloys can sometimes react with or inhibit silicone curing. Oily metals or those with protective coatings may require surface treatment before application.
The key is proper surface preparation—clean, dry and free of contaminants—regardless of the metal type.
Start by considering where the sealant will be used. Will it see direct sunlight? Extreme temperatures? Saltwater or chemical exposure? Then check the metal type and any compatibility issues. Finally, look at the movement expected in the joint—high-movement applications need more flexible formulations.
When in doubt, consult the manufacturer’s technical data sheet or work with an experienced fabricator who’s dealt with similar applications before.
Yes, but it takes effort. Old silicone needs to be completely removed—scraped and cleaned away—before applying new sealant. Any residue left behind will prevent proper adhesion of the new silicone.
Use a silicone remover or solvent recommended for your metal type, then clean thoroughly with isopropyl alcohol. Make sure everything is completely dry before applying fresh sealant. Shortcuts here almost always lead to early failure of the new seal.
Rich Marker is an 18 year, skilled professional in metal fabrication and manufacturing. Co-founder, owner and principal of All Metals Fabrication, Rich has helped to sustain the company’s success over a variety of economic conditions. He has extensive background in continuous improvement, training and process improvement, and emotional intelligence—among other specialized proficiencies. He loves to learn, fly fish, watch college football and devour NY style pizza! He has the best family on earth, loves a good plan, great teaching and the opportunity to get better.
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