TECH TIP: Hydrogen Sulfide

By Joe Sarver

Hydrogen sulfide is a chemical compound with the formula name H2S. In simple chemistry terms it’s two atoms of hydrogen bonded with one atom of sulfur. Hydrogen sulfide gas is commonly associated with the smell of rotten eggs and flatulence. It is a naturally occurring substance found in volcanic eruptions, natural gas and even some well water. In fact, the Jefferson Pools located in Hot Springs, Virginia hailed by Thomas Jefferson for their medicinal benefit also contain dissolved concentrations of hydrogen sulfide gas and actually give off a mild rotten egg aroma. This compound can also be found in man-made industrial environments such as fuel refineries, waste water/sewage pumping and treatment facilities and even some paper plants.
As seen from the toxicity chart on this page, with higher concentrations comes severe health and even lethal consequences. While many of us are familiar with hydrogen sulfide’s odor properties (typically evident at lower concentrations), we are largely not aware of its corrosive properties especially when it comes to electronics—specifically printed circuit boards. The corrosion can occur at lower concentrations as well. The electronic damage usually will manifest itself as a result of chronic lower concentrations of hydrogen sulfide but can certainly set in with exposure to higher concentrations over shorter periods of time.
One commonly used method of treating H2S induced corrosion is with the application of an after-market conformal coating on printed circuit boards provided by some service and repair providers. This will usually mitigate the corrosion damage all right. However, an unwanted “side effect” of after market board coatings is that they can de-rate the heat tolerance of electronic components. In other words, the conformal coating can actually inhibit the heat dissipation capability of electronic components and this can lead to heat induced, pre-mature failures.
Through our extensive field and bench repair experience Delta Automation has determined that the best way to minimize electronic component failure is to:
1. Keep the board components clean and free of moisture and/or condensation.
2. Maintain positive pressure inside the equipment panels with respect to the ambient room pressure via the use of an inert gas such as argon. 3. Use equipment that has OEM applied conformal coatings. OEM coatings are more effective than after market applied coatings because the heat dissipation effects of the coating are designed into the heat capacity of the installed electronic components.
Let Delta Automation answer all your questions about how to maximize the service life and dependability of your systems’ electronic components.

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About deltaautomation

President of Delta Automation, Inc. Working in industrial automation in excess of 30 years
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