As a supplier of small air separation units (ASUs), I’ve spent over a decade working with workshops, small-scale manufacturing plants, and remote mining operations that rely on compact, reliable equipment. The most common issue I hear from customers isn’t about performance—it’s about corrosion. For small ASUs, which are often installed in less controlled environments, corrosion can slow production, raise maintenance costs, and even shorten a unit’s lifespan by half if left unaddressed. I’ve learned that corrosion prevention isn’t just a technical detail—it’s a core part of how we design and support the small ASUs we deliver. Let’s break down the measures that actually work, based on what I’ve seen in the field and tested in our own facility. Small Air Separation Unit
First, let’s start with the basics: understanding where corrosion hits a small ASU hardest. These units aren’t the giant, insulated industrial systems you see at steel mills. They’re compact, with thin-walled pipes, heat exchangers, and pressure vessels, all exposed to ambient conditions. The main culprits are atmospheric moisture (especially if the unit is installed in coastal areas, high-humidity regions, or near water sources), trace contaminants in the feed air (like sulfur dioxide from nearby factories or salt spray), and even condensation from the compression process inside the unit. For small operators, this means the parts that move or hold gas—piping, valves, and the aluminum or steel heat exchangers—are the most vulnerable. A single rust spot on a small pipe can lead to a leak that stops production, and with a small unit, downtime costs add up fast because you’re running fewer overall operations.
The first line of defense, and one we prioritize in every unit we ship, is material selection tailored to the operating environment. Not all small ASUs are installed the same way, so one size doesn’t fit all here. For example, if a customer is in a arid, low-humidity region, our standard carbon steel piping works, but we add a specific coating that resists minor dust and debris. For customers in coastal areas or high-humidity zones, we swap out carbon steel for galvanized steel or, even better, 304L stainless steel for the main gas handling components. We also use aluminum alloys for the heat exchanger cores, which are naturally corrosion-resistant but require a specific finish if exposed to salt air. I remember a customer in a coastal mining town a few years back: they had a used small ASU that failed after 18 months because their previous supplier used uncoated carbon steel pipes. We redesigned their unit with 316L stainless steel valves and added a powder coat to all external steel parts, and two years later, they haven’t had a single corrosion-related issue. That’s the kind of result that matters for small operators, who can’t afford to replace parts every couple of years.
Next, active corrosion control through the unit’s air treatment system. The feed air that goes into a small ASU isn’t pure—it has moisture, dust, and corrosive gases, and if that air isn’t treated before it enters the compression cycle, it will cause corrosion from the inside out. We integrate a two-stage pre-treatment system into every small ASU we sell, and I can’t stress how important this is. The first stage is a coalescing filter that removes liquid water and large particulates. Water is the biggest driver of internal corrosion, so getting rid of it before it enters the compressor and distillation column is non-negotiable. The second stage is an adsorption dryer, usually using molecular sieves, that removes water vapor down to a dew point of -40°C. That means even in high-humidity climates, the air inside the unit stays dry enough to prevent rust from forming on internal metal parts. We also add an activated carbon filter to trap trace contaminants like sulfur compounds and volatile organic compounds (VOCs) that would otherwise accelerate corrosion. A customer in a chemical processing plant told me they used to have to blow down their ASU’s distillation column every six months to remove corrosion residue; since we added that pre-treatment system, they only do it every three years. That’s a huge maintenance saving for a small operation.
Then there’s passive protection for external components. A small ASU is often installed in a semi-outdoor space or a simple shelter, not a climate-controlled facility, so external parts need extra protection. We use several methods here, starting with proper surface preparation before coating. For any steel parts, we sandblast them to remove rust, mill scale, and contaminants before applying a two-part epoxy coating. This isn’t the cheap spray paint you might buy at a hardware store—it’s a heavy-duty coating designed to resist chipping, UV damage, and moisture. We also apply a sealant to all threaded connections and joints, which are common spots where moisture can seep in. I’ve seen customers skip this step because it adds a little cost, but within a year, those joint areas start to rust. We include the sealant as a standard part of our unit installation kits, so operators don’t have to worry about forgetting it. For parts that can’t be coated, like aluminum heat exchanger fins, we use a corrosion-resistant inhibitor spray that we apply during the manufacturing process; it doesn’t interfere with heat transfer, but it repels moisture and salt.
Another key measure is regular monitoring and maintenance, which we train all our customers to do—because even the best-designed corrosion-prevention system will fail if ignored. For small ASUs, maintenance doesn’t have to be complicated. We provide a simple checklist that operators can go through monthly: checking for rust spots on external pipes and valves, testing the pre-treatment filters to make sure they’re not clogged, and draining any accumulated water from the unit’s low-point drains. We also recommend a quarterly inspection of internal components, but for most small operators, that’s a service we can provide as part of our after-sales support. One mistake I see a lot of new operators make is skipping the filter replacement, which lets contaminants build up and cause internal corrosion. We send automated filter reminder alerts to our customers, and we keep replacement filters in stock for fast delivery, so they don’t have to wait weeks for parts.
There’s also a newer measure we’ve started offering for our small ASUs: internal corrosion inhibitors, which are injected into the gas stream in small, controlled doses. Unlike external coatings, these inhibitors form a thin, protective layer on the inside of pipes and pressure vessels, preventing water and corrosive gases from reacting with the metal. They’re especially useful for operators who use their ASU to produce nitrogen for blanketing or other applications where the feed air has high levels of contaminants. We calibrate the inhibitor dosage for each unit based on its operating conditions, so it doesn’t affect the purity of the gas output. A customer who uses their small ASU to purge natural gas pipelines told us this reduced their corrosion-related maintenance by 70%—they used to replace a valve every year, and now it’s been three years without a replacement.
Wait, but I should be honest here: no corrosion-prevention measure is perfect, especially for small ASUs that are often pushed to their limits. We’ve had customers try to cut costs by installing a used unit or skipping some of our recommended steps, and they end up dealing with corrosion issues. That’s why we don’t just sell a unit and walk away—we work with each customer to customize the corrosion-prevention plan for their specific operating environment. If someone is installing the unit in a remote, dusty location with no access to regular maintenance, we add extra coating layers and a self-draining system to prevent water buildup. If someone is in a laboratory with very clean air, we can adjust the pre-treatment system to be slightly less robust, which saves them money on upfront costs.
I also want to address a common misconception: small ASUs are more prone to corrosion than large ones, but that’s not entirely true. The difference is that large ASUs have dedicated maintenance teams and climate-controlled facilities, while small ASUs are often operated by small teams who don’t have specialized corrosion knowledge. That’s why our approach to corrosion prevention is centered on making it easy for our customers. We design our units to have easily accessible parts, clear labeling for maintenance, and simple systems that don’t require advanced training to operate. For example, our low-point drains are color-coded so operators know exactly where to check for water, and our filter change-outs take less than five minutes, no special tools needed.
Looking back at my career, the most satisfying projects have been when we help a small operation avoid corrosion-related downtime. Last year, a small farm that uses a 50 LPM ASU to produce nitrogen for their crop spraying equipment reached out to us because their previous unit had corroded so badly it leaked during a harvest. We replaced it with a unit tailored to their outdoor installation: 316L stainless steel valves, a heavy-duty epoxy coating, and a pre-treatment system sized for the dusty, humid air on their farm. Six months later, they told us the unit was running perfectly, and they’d already saved enough on maintenance costs to cover the difference between our unit and the cheaper one they’d bought before.
At the end of the day, corrosion prevention for small ASUs isn’t just about materials and systems—it’s about understanding that our customers rely on these units to keep their operations running. We don’t sell a machine; we sell a reliable solution, and part of that reliability is making sure it doesn’t corrode when they need it most. If you’re in the market for a small air separation unit, whether for industrial, agricultural, or commercial use, don’t just look at upfront cost—ask about the corrosion-prevention measures we build into every unit, and let’s talk about how we can customize a plan that works for your environment and your needs. Reach out to our team to learn more, and we’ll be happy to walk you through our units, share case studies from other customers, and answer any questions you have.
Air Separation Unit References
- ASHRAE Handbook: HVAC Systems and Equipment, Chapter 12, Compressed Air Systems
- NACE International. (2020). Corrosion Control for Pressure Vessels and Piping in Small Industrial Plants
- Air Separation Equipment Manufacturers Association (ASEMA) Best Practices for Small ASU Operation and Maintenance
- Stainless Steel Industry Association. (2019). Corrosion Resistance of 304L and 316L Alloys in Atmospheric Environments
Xinxiang Jiale Intelligent Equipment Co., Ltd.
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