Preventing Corrosion: Choosing the Right Materials for Industrial Filtration Systems

By most measures, industrial fluid processes and utility systems have it rough. Continuous operating duties, extreme temperatures, and pressures, and inhospitable environments - are just a few of the normal conditions that come along with industrial processes. In a perfect world, all piping components in a facility would receive thorough, frequent inspections and preventative maintenance, proactively catching issues before they occur. In reality, such action might as well be impossible, between the sheer magnitude of the task at your average-size facility and the fact that piping components tend to fail from the inside, where visual signs of concern are concealed. With that said, there are still moves we can make toward ensuring the long, safe operation of our process and utility piping systems, starting with defending against corrosion.

Let's kick off the discussion with a few statements about corrosion:

• Corrosion is an electrochemical reaction that leads to material loss in metals, as well as in some plastics and ceramics.
• In industrial piping applications, corrosion typically occurs when dissimilar materials are directly connected, creating an electrical gradient that makes ion exchange imminent.
• Fluids moving through or over piping (and their chemical compositions, temperatures, and pH levels) initiate and accelerate the chemical reactions that lead to this ion exchange. Over time, this ion exchange results in material degradation.
• Corrosion can occur both inside and outside of a piping circuit, leading to discoloration, gradual material weakening, and eventually, unexpected failures.

Once corrosion begins, it's only a matter of time before enough material loss has occurred that piping components will spring leaks. The severity of such a failure is entirely dependent on the fluid, pressure, and mechanical stresses in play, but can generally range from a pinhole leak to a massive sidewall rupture. For this reason, maintenance and engineering leaders have major responsibilities in preventing corrosion-induced failures in both new and existing systems. In our opinion, the first step in avoiding such problems is to select the right materials for industrial piping components (and all other critical infrastructure), ensuring complete compatibility with the expected application at hand. Thereafter, robust ongoing inspections and non-destructive testing (where needed) should become routine procedures, all in the pursuit of catching corrosion as early as possible.

Material Selection for Industrial Filtration Components

Now that readers understand that the best corrosion defense is to stop it before it begins, we can introduce the topic of material selection as it relates to corrosion resistance. In short, selecting materials that are corrosion-resistant in a specific application means minimizing the potential for rogue chemical reactions to occur. Below we’ll present the most common industrial piping materials and describe each in terms of their typical applications. Since our expertise is in industrial filtration, this list reflects filtration system projects and is not all-inclusive of all possible materials.

Beyond the above materials, additional exotic alloys and compositions are available for special applications. For example, Hastelloy C276, Glass-Reinforced Polypropylene, and Titanium B367 materials can be furnished for extremely demanding chemical, temperature, and environmental duties.

Application Considerations to Defend Against Corrosion

Before settling on a final material decision for your next industrial filtration project, review these few additional application considerations which may present a different selection as most ideal.

• After a base material is selected for its compatibility with your application, additional finishing options are often available to enhance further corrosion resistance including spray coating, electroplating, electropolishing, hot dip galvanizing, and painting.
• Be sure to check chemical compatibility using an index rating from a reputable source. Ideally, use a compatibility chart from the manufacturer of the filtration components you’re purchasing, as the OEM will have considered the exact alloy, treatment, and finish of their equipment when setting their ratings.
• Make sure to consider the actual temperatures and pressures, chemical concentrations, and environmental conditions expected, which may individually or collectively impact a given material's resilience against corrosion.
• For highly advanced applications, or whenever an expert opinion will bring peace of mind, consult with a technical sales associate or engineer to make sure your material selection covers all bases. For example, multi-stage membrane filtration systems may experience hydraulic conditions that can exacerbate mild corrosion susceptibility. For example, certain environmental factors such as extended UV exposure can do the same.
• Remember that most rapid corrosion stems from the connection of dissimilar metals. Work with a qualified engineer or contractor during installation who will be responsible for mitigating corrosion risk throughout the piping circuit. This may require unique piping connections, sacrificial anodes, grounding jumpers or rods, non-metallic piping spools, or other custom solutions to properly address the risks. Also, many corrosion-mitigating aspects of an installation are governed by ASME, plumbing, or similar codes, which a licensed engineer or contractor will be familiar with.
• Once new components are installed, be sure to perform intrusive inspections during the first few months to catch any major signs of a compatibility error. For materials that are coated or painted, these inspections should continue longer to monitor the wear rate of the coating (and to accurately forecast when recoating shall be performed).
• For mission-critical components, consider performing non-destructive testing regularly. Test methods such as borescope, x-ray, eddy current, and infrared inspections can often show measurable indicators of corrosion well before they can be caught by the naked eye.
• With nearly all services and media, corrosion is unavoidable over a long enough time.
• For general piping applications, published reference data is available that states a material’s general service life duration.
• For special applications where general information is not available, non-destructive testing is paramount. Testing can be done early on to establish a baseline measurement for piping and component sidewalls, and then over time, additional measurements can tell how fast the material is degrading such that an end-of-life date can be discerned.
• In both cases, recoating and relining piping components may extend their lifespans for a time. Eventually, replacement components should be installed and old circuits decommissioned well ahead of their end-of-life dates.

Recap

No matter the cause, corrosion in industrial piping systems – and their inline components – can lead to significant damage, financial loss, downtime, and worse outcomes. Managing the risk of corrosion begins with selecting the most compatible materials for your application, from filtration components to all others. Next, components must be installed in ways that dissuade the electrochemical reactions leading to corrosion, which takes technical knowledge and experience in both regulatory codes and practical material sciences. After these steps are properly taken, we’re left with a small amount of corrosion risk due to environmental and incidental factors, which can be further managed through ongoing, proactive maintenance, inspections, and non-destructive tests. Altogether, corrosion does not need to be a silent threat waiting to strike but instead can be relegated to just another routine maintenance check that your team has mastered.