Hey there, fellow container enthusiasts and anyone who’s ever stared at a massive steel box on a ship or a warehouse loading dock and wondered, “What even is that thing made of?” Steel Container
For the last 12 years, I’ve been running a small steel container supply company—you know, the guys who ship these bad boys all over North America, fix up the dented ones, and send new ones to businesses that need reliable storage or shipping. I get so many questions from new customers, like “Why is my shipping container rusting in spots?” or “Can I use this for my outdoor workshop?” And almost every time, the first thing I need to break down is the steel. Because let’s be real: the type of steel we use makes all the difference between a container that lasts 20 years and one that needs replacing in five.
I’ve lost count of how many times a customer has come to us thinking all steel is the same. Spoiler alert: it’s not. I once had a guy who tried to cut open a container with a torch to turn it into a pool, and he was shocked when it took him twice as long as he expected—turns out he was comparing our shipping-grade steel to some flimsy sheet metal he had at home. That’s why today, I’m pulling back the curtain on exactly what types of steel we use here at our company, why we pick them, and how each one fits different jobs. Let’s dive in.
First up, the workhorse of almost every standard shipping container out there: Corten steel. You’ve probably heard us mention it before, but let’s get into the nitty-gritty. Corten is short for “corrosion-resistant tensile steel”—sounds fancy, right? But what that actually means is it’s a weathering steel, made with a mix of iron, carbon, and small amounts of copper, chromium, and nickel. Here’s the cool part: when it’s exposed to the elements, it develops that brownish-orange patina you see on old shipping containers. That patina isn’t just rust—it’s a protective layer that seals the steel underneath, so it doesn’t corrode any further. That’s why shipping containers hold up so well crossing the ocean in salt air, or sitting in the sun and rain for decades.
Wait, but hold on—there’s a common myth about Corten. Some people think you can paint over it, and that’s fine, but a lot of folks think it’s 100% rust-proof, and that’s not true. It just rusts on the surface, and then stops. Our standard dry van shipping containers use Corten for almost everything: the side panels, the roof, the floor framework, the corner posts. It’s strong enough to stack nine high on a cargo ship, flexible enough to handle being dragged off a truck, and doesn’t cost a fortune compared to other steels. We went with Corten for our base model because it checks every box for regular shipping and storage. I’ve seen containers we sold in 2010 that are still going strong out in Texas—sunny, windy, and occasionally hailing—and they don’t have a spec of structural rust. That’s the Corten doing its job.
Next, let’s talk about the stuff that keeps those containers from collapsing when you stack them: high-strength low-alloy (HSLA) steel. Wait a second—isn’t that the same as Corten? No, not exactly. HSLA steel is a broader category, and Corten is actually a type of HSLA, but we use a different grade specifically for structural parts. The corner castings, the crossbeams under the floor, the vertical posts that run the height of the container—all that is HSLA. We use HSLA-80, to be specific. The “80” stands for its tensile strength, which is 80,000 pounds per square inch. For reference, regular carbon steel is around 60,000 psi. So HSLA is way stronger, without being way heavier. That’s a big deal because shipping containers need to be light enough to move on trucks and ships, but strong enough to carry 60,000 pounds of cargo inside. If we used regular carbon steel for the corner castings, they’d be heavier, which would cut into how much cargo a container could hold. And no one wants to pay extra in shipping costs just because the container itself is overweight.
I remember when we first switched to HSLA-80 a few years back. We were getting calls from customers complaining that their containers’ corner posts were bending when they stacked heavy equipment inside. The manufacturer we worked with at the time was using a cheaper HSLA grade, and it just wasn’t up to par. We did months of testing—loading 10,000-pound blocks into containers, stacking them seven high in our warehouse for a year, even putting them through our own simulated salt spray test. Once we switched to HSLA-80, those complaints stopped cold. It’s tougher, more resistant to dents and bends, and it holds up way better under repeated stress. That’s the steel you want if you’re using your container for something heavy—like storing construction materials, or as a temporary office for a job site.
Now, what about the floor? Most people don’t think about the floor of a container, but it’s one of the most important parts. A container’s floor has to hold thousands of pounds of pallets, forklifts, and whatever else you’re hauling or storing. For standard containers, we use two main types for floors, depending on if it’s a new build or a refurbished one. New containers use marine-grade plywood, but we supplement that with steel floor plates along the edges where forklift tires drive. Wait, hold up—wait, is that steel? Yes, the floor edges. Because forklift forks are metal, and if you drive a forklift right on the edge of the plywood floor for years, it’s going to wear through. So we add 1/8-inch thick cold-rolled steel plates along the bottom two feet of each side of the floor. That’s cold-rolled steel, by the way—another type I haven’t mentioned yet. Cold-rolled is just steel that’s been shaped at room temperature, instead of hot, so it’s smoother and stronger for its thickness. It’s not as corrosion-resistant as Corten, but it’s perfect for this job because it’s cheap, easy to cut and weld, and it takes the abuse from forklifts way better than plywood.
For our refurbished containers, we usually replace the plywood floor with a recycled steel floor—cold-rolled, again. Why? Because a lot of refurbished containers are used for temporary storage at construction sites, where forklifts are constantly dragging across the floor, and the old plywood is just going to get ruined in a few months. Steel floors are way more durable for that kind of use, even if they’re a little noisier when you roll a dolly over them. We always tell customers: if you’re storing light stuff like boxes, go with the plywood floor. If you’re driving forklifts or heavy equipment in there, get the steel floor upgrade. It’s worth the extra $200, trust me.
Now, let’s talk about specialty containers, because not everyone wants a standard 20-foot or 40-foot dry van. We build a lot of specialized containers for things like refrigerated units, hazardous material storage, and even mobile clinics. Those use different steels, and for good reason. For refrigerated containers (reefers), the inner liners are made of 304 stainless steel. Wait, that’s another steel grade—stainless steel, which has at least 10.5% chromium, so it’s super resistant to corrosion from moisture, food, or chemicals. If we used Corten for the inner liner of a reefer, all the condensation from the cooling unit would make it rust on the inside, and you’d end up with stains on your produce or whatever you’re shipping. 304 stainless is easy to clean, doesn’t rust, and holds up to the constant temperature changes in a refrigerated unit. It’s a little more expensive than Corten, but for reefers, it’s non-negotiable.
Then there’s hazardous material containers. Those are a whole different ballgame. For containers that hold flammable liquids or corrosive chemicals, we use high-density polyethylene (HDPE) lined steel, or sometimes 316 stainless steel. 316 stainless is even more corrosion-resistant than 304—it has molybdenum added, which makes it stand up to salt, acids, and harsh chemicals. We had a customer a couple years ago who needed a container to store industrial cleaning chemicals, and the 304 stainless we quoted them on started to get pitted after a month of testing. Switched to 316, and it’s been perfect for two years now. The downside is it’s way pricier, so we only use it for specialty hazmat jobs.
Wait, I should also mention what we never use. A lot of cheap container sellers out there use regular mild carbon steel for structural parts, just to cut costs. But mild steel rusts super easily, and it’s way weaker than HSLA or Corten. We once had a customer bring us a container he bought from a guy online, and the corner posts were just regular steel—they were so rusted, you could poke a hole in them with a screwdriver. He paid half what our containers cost, and it was falling apart after a year. That’s the kind of junk we refuse to sell. For us, the steel type isn’t a choice—it’s a promise. Our containers have to stand behind their work, so we don’t cut corners on materials.
I get it—when you’re shopping for a steel container, you’re focused on size, price, and whether it’ll hold all your stuff. Steel type might not be the first thing on your mind. But trust me, it matters. If you’re buying a cheap container with mild steel, it’ll rust out in half the time, and you’ll end up spending more money replacing it. If you buy one with the right Corten and HSLA steel, it’ll last you 20, 30 years, maybe even longer. We have customers who’ve had our containers for 15 years, they use them for storage, and they still look almost as good as the day we delivered them.
Let me leave you with a quick tip the next time you’re checking out a container. Run your hand along the roof and side panels—if it’s Corten, it should feel slightly rough, not smooth like paint. Tap on the corner posts—if they sound hollow or weak, that’s a sign they used cheap steel. Check the floor edges where forklifts drive—if there’s no steel plate there, it’ll wear through fast. These are small things, but they make a huge difference.
If you’re in the market for a steel container—whether it’s a standard 20-foot shipping unit, a modified office container, a hazmat storage unit, whatever—we can hook you up. We sell new and refurbished containers, deliver anywhere in the country, and we’ll even help you pick the right steel type for your specific needs, no jargon, no pressure. Just reach out to our team to chat about what you’re looking for. We’ve got over a decade of experience, and we don’t sell anything we wouldn’t use ourselves.
Don’t waste your money on flimsy, cheap containers that’ll fall apart in a few years. Invest in a steel container made with the right materials, and you’ll have a reliable space for all your stuff for decades to come.
Push Back Racking References:
- ASM International. (2005). Atlas of Stress-Corrosion Cracking. Materials Park, OH: ASM International.
- British Standards Institution. (2016). BS EN 10025-5: Hot rolled products of structural steels. Part 5: Technical delivery conditions for weathering steels. London: BSI.
- International Organization for Standardization. (2018). ISO 1496-1: Series 1 freight containers – Specification and testing – Part 1: General cargo containers for general purposes. Geneva: ISO.
- Corus Steel. (2010). Corten Steel: Properties and Applications. IJmuiden: Tata Steel Europe.
Nanjing Jinhui Storage Equipment Co., Ltd.
Nanjing Jinhui Storage Equipment Co., Ltd. is one of the leading steel container manufacturers and suppliers in China, engaged in customized service. Feel free to buy the best quality steel container for sale here and get quotation from our factory. For price consultation, contact us.
Address: NO.22, Ankang Road, Guli concentrated zone, Nanjing City, China.
E-mail: export@jhrack.com
WebSite: https://www.cn-rack.com/
