40 n DRIVE RELIABILITY July/August 2025 www.drivesncontrols.com Corrosion: the hidden threat to VSD reliability Manufacturers are right to focus on performance, energy efficiency and uptime for their equipment. But despite these priorities, there is a costly, and often invisible, threat that continues to grow: corrosion. The global impact of corrosion is enormous, with the Association for Materials Protection and Performance estimating that losses amount to $2.5 trillion annually. For VSDs (variable-speed drives), corrosion can lead to catastrophic failures – often without warning. In sectors such as rubber, plastics, mining and water treatment, the combination of heat, humidity, chemicals and dust, creates the perfect conditions for a drive to deteriorate. But unlike mechanical wear, corrosion flies under the radar. It can strike both internal and external components, from power assemblies to circuit boards and seals, and often surfaces outside warranty, when failure is most costly. In fact, a single hour of production downtime caused by a failed drive can cost upwards of £90,000. Corrosion is typically defined as degradation caused by chemical interaction between materials and their environment. “Electronic corrosion” includes damage to crucial components such as PCBs, IGBTs, thermal interfaces and connectors. Humidity, pollutants such as sulphur dioxide, as well as reactive particles, settle on sensitive surfaces, enabling electrochemical reactions that erode functions over time. Polymers used in plastic or rubber enclosures and seals can also degrade through exposure to chemicals. These failures can go unnoticed until they result in leaks, failed seals, or even complete enclosure breaches. Complicating matters, modern drives are designed to be compact and high-performing, generating more heat and thus requiring more airflow. Both of these factors can increase exposure to corrosive agents if protection isn’t engineered properly. Superficial signs such as rust marks might be an eyesore, but they’re ultimately harmless. “Silver whiskers”, however, are far more dangerous. These are microscopic hair-like structures caused by sulphur that can create unintended electrical pathways and lead to system faults or complete failures. This kind of corrosion is particularly harmful because it’s hard to detect and even harder to diagnose. High humidity, sudden changes in temperature, and chemical by-products from industrial processes make industries such as rubber and plastics, pulp and paper, and wastewater, particularly vulnerable. Equally at risk are emerging markets in Asia and Africa, where challenging environmental conditions – such as temperatures above 45°C and high humidity – combine with rapid industrial growth. Standards gap Despite the importance of the issue, outdated standards such as IEC 60721-3-3:2002 still determine the design of much of today’s equipment. Labels such as 3C3 frequently appear in drive specifications, but lack realworld testing or clear pass/fail criteria. This creates a false sense of protection. A coated PCB may check a box, but it may not stand the test of time in a corrosive environment. The good news is that newer standards – such as IEC 60721-3-3:2019 – are shifting the focus from theoretical gas exposures to actual corrosion impact. They classify environments from G1 (mild) to GX (severe), based on how much metal corrosion occurs over 30 days. However, this standard doesn’t specify how drives should be tested, resulting in a crucial gap. To address this, ABB has developed a rigorous testing protocol for VSDs. Working with Lappeenranta-Lahti University of Technology in Finland, not just individual components, but live drives, were subjected to high concentrations of industrial gases, extreme temperatures, and humidity. Then, using techniques such as thermal imaging and electron microscopy, we evaluated the entire drive, including cooling fans, connectors, and internal electronics. This level of testing reveals hidden weaknesses and validates which protections actually work, far beyond surface coatings. The findings were clear: drives housed in IP55 (UL Type 12) enclosures with reinforced seals fared significantly better than IP21 (UL Type 1) models. For high-risk environments such as tyre manufacturing with sulphur-rich air, ABB is now offering ruggedised VSDs rated for extreme C5/CX or GX conditions, and capable of withstanding corrosion rates up to 8,000 angstroms over 30 days. Corrosion rarely gives an early warning and often strikes after a drive’s warranty expires. But understanding its causes and the limitations of existing standards is a first step towards avoiding downtime and protecting workers. While some corrosion may be unavoidable, drive failures do not have to be. With the right protections and protocols, VSD lives can be extended significantly, and system reliability can be ensured, in even the harshest environments. n Corrosion is often overlooked as a failure risk for industrial drives. Traditional corrosion standards can fall short when applied to drives. Fausto Belotti, global segment manager for rubber and plastics in ABB Drive Products, describes a new test method that helps to predict drive lifetimes in harsh environments Examples of how corrosion can affect different parts of VSDs
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