Electronics corrosion occurs when moisture, oxygen, salts, or contaminants react with conductive metals on a PCB or electronic assembly. It can cause leakage current, short circuits, increased contact resistance, intermittent failures, and long-term reliability degradation. Engineers prevent corrosion through environmental sealing, material selection, PCB cleanliness controls, conformal coatings, and reliability testing — ideally designed in from the start rather than addressed after field failures appear.
Electronics corrosion occurs when moisture and contaminants create electrochemical reactions on conductive surfaces over time. PCBs, connectors, solder joints, and exposed metals are particularly vulnerable in environments with humidity, ionic contamination, or repeated thermal cycling.
Common corrosion drivers include:
Corrosion can produce immediate failures or latent defects that emerge months after deployment. This makes corrosion especially difficult for reliability engineers because failures are often intermittent and difficult to reproduce consistently during analysis.
Moisture and ionic contamination create unintended conductive paths across PCB surfaces. Leakage current can alter signal behavior, interfere with sensors, drain batteries, and produce unpredictable system operation.
Conductive corrosion residues can bridge adjacent conductors and create shorts. Fine-pitch assemblies are especially vulnerable because minimal contamination can establish electrical pathways across narrow spacing.
Electrochemical migration (ECM), also known as dendritic growth, occurs when metal ions move across an insulating surface while under an electrical bias in the presence of moisture. Over time, these conductive metal dendrites, resembling branching tree structures, grow between conductors and eventually create intermittent or permanent short circuits. For dendritic growth to occur, ionic residue, water, and electrical bias all need to be present, and removing any one of these will prevent dendrites.
Corrosion on connectors, terminals, and solder joints increases electrical resistance, leading to voltage drops, localized heating, signal integrity problems, and degraded system performance.
Corrosion also weakens solder joints, connector surfaces, and component leads. Even minor degradation can contribute to failure under vibration, thermal cycling, or mechanical stress.
This progression explains why corrosion failures are difficult to diagnose — assemblies may continue functioning for extended periods before intermittent field faults begin appearing.
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Engineers should evaluate corrosion risk based on actual operating conditions, expected service life, enclosure strategy, and reliability requirements.
| Environment | Corrosion Risk Factors | Common Design Concern |
| Automotive and mobility | Humidity, condensation, road salt, thermal cycling | Long-term PCB reliability across vehicle service life |
| Industrial electronics | Chemicals, airborne contaminants, washdown, humidity | Resistance to corrosive atmospheres and process fluids |
| Medical devices | Biofluids, cleaning agents, and sterilization exposure | Reliability across sterilization cycles |
| IoT and outdoor devices | Rain, condensation, UV exposure, temperature variation | Moisture protection with minimal size/weight impact |
| Aerospace and defense | Humidity, salt fog, altitude, thermal shock | Mission-critical operational reliability |
| Consumer electronics | Sweat, spills, humidity, handling | Warranty reduction and durability improvement |
Corrosion prevention is most effective when incorporated early in the design process. Retrofitting protection after failures occur is typically more expensive and less reliable.
Common prevention strategies include:
Conformal coatings protect electronic assemblies by creating a barrier between conductive surfaces and the surrounding environment. Different coating chemistries offer different tradeoffs in barrier performance, thickness, flexibility, chemical resistance, and reworkability.
| Coating Type | Moisture / Corrosion Protection | Key Strength | Common Tradeoff | Best For |
| Acrylic | Moderate | Easy application and rework | Lower chemical resistance | General-purpose protection |
| Silicone | Good | Flexibility and temperature resistance | Can pool on complex geometries | High-temperature assemblies |
| Urethane | Good | Chemical and abrasion resistance | Difficult to rework | Chemically aggressive environments |
| Epoxy | High | Durability and chemical resistance | Rigid and difficult to remove | High-stress environments |
| Parylene | Excellent | Ultra-thin, pinhole-free conformality | Requires vapor deposition | Miniaturized, high-reliability electronics |
View our corrosion protection webinar
Parylene is a vapor-deposited conformal coating used when engineers require thin, highly uniform protection across complex geometries. Unlike liquid coatings applied by spray, brush, or dip, Parylene forms a continuous polymer film through gas-phase deposition — reaching under components, along leads, and into gaps that liquid coatings may bridge or leave thin.
For corrosion prevention, Parylene offers several advantages:
Parylene is often selected when high conformality, thin-film protection, dielectric performance, or coverage consistency is critical for long-term reliability.
Parylene is often a strong fit when applications involve:
View our Parylene Considerations Webinar
Because corrosion is environment-dependent, engineers validate protection strategies through testing that reflects actual exposure conditions.
Common evaluation methods include:
The appropriate test plan depends on product category, operating conditions, regulatory requirements, and expected service life.
Visible corrosion can sometimes be cleaned from electronic assemblies using appropriate solvents and inspection methods. If you’re dealing with a corroded or water-damaged device, here are the general steps involved:
Cleaning is not the same as restoring full reliability. Corrosion can leave latent damage that is difficult to detect visually and may manifest as intermittent failures later. For OEMs and product engineers, prevention is significantly more reliable than post-failure remediation.
PCB corrosion is most commonly caused by moisture, oxygen, ionic contamination, salts, and electrical bias acting on conductive metal surfaces. Flux residues and handling contamination left over from manufacturing can increase surface conductivity and accelerate corrosion when moisture is present — particularly in environments with repeated thermal cycling that causes condensation to form and evaporate over time.
Yes. Humidity can initiate corrosion, leakage current, electrochemical migration, and short circuits — especially in environments with repeated thermal cycling and condensation. The risk compounds over time as ionic contamination accumulates on unprotected surfaces with each condensation cycle.
Conformal coatings reduce corrosion risk by creating a protective barrier between the assembly and environmental exposure. Protection effectiveness depends on coating chemistry, thickness, coverage uniformity, and application quality. Parylene typically provides the highest barrier performance due to its vapor-deposition process, which achieves uniform, pinhole-free coverage on complex surfaces where liquid coatings may have thin areas with insufficient protection, and/or thick areas where coating pools, which may lead to mechanical damage after undergoing thermal cycling due to mismatched coefficients of thermal expansion (CTEs).
There is no single best coating — the right choice depends on the application. Acrylics offer easy rework for general-purpose use. Silicones withstand wide temperature ranges. Urethanes and epoxies provide strong chemical resistance. Parylene offers the highest conformality and barrier performance, making it well-suited for miniaturized, high-reliability, or medically implanted electronics. See the comparison table above for a side-by-side overview.
Yes. Parylene forms a thin, pinhole-free polymer film across all exposed surfaces — including under components, along leads, and on sharp edges — that acts as a barrier against moisture, ionic contaminants, and corrosive chemicals. Its vapor-deposition process ensures uniform coverage on geometries where liquid coatings cannot achieve consistent thickness.
Corrosion can begin within hours of moisture exposure or remain latent for months before causing failure. The rate depends on humidity, contamination, voltage bias, thermal cycling, and the presence of protective coatings.
Corrosion prevention is ultimately a design and reliability challenge. Engineers must account for operating environments, contamination risks, coating selection, and validation requirements before products reach the field.
HZO helps companies protect electronics from corrosion, moisture, and harsh environments with thin-film coating solutions including Parylene. If your team is evaluating conformal coating options for a new product or reliability improvement program, request a coating evaluation for your specific application — or explore our protection capabilities to learn more about what Parylene coating can do for your design.