Does Your Sensor Have Chemical Compatibility?

You may have the best sensor on the market, but if its materials aren’t compatible with the media you’re measuring, performance and reliability are immediately at risk. Incompatibility can lead to sensor failure, inaccurate readings, unplanned downtime, and costly replacements.

In short, successful sensor selection requires good chemistry between your sensor materials and the chemicals they encounter.

Chemical compatibility refers to a material’s ability to resist chemical attack, degradation, or reaction when exposed to a specific substance over time. At Automation Products Group, Inc. (APG), we offer several sensors that have good chemical compatibility. Here are a few general rules and guidelines to help you find a starting place in your research and testing. Chemical compatibility is influenced by three key factors: the chemical itself, the sensor material, and the operating temperature. Let’s start with a look at some common materials.

Metals

Metal-bodied sensors are often selected for strength and temperature resistance, but not all metals perform equally in chemical environments. Stainless steel is highly versatile, making it ideal for applications involving non-corrosive substances like diesel fuel. For more demanding environments, titanium offers superior resistance to corrosive environments, including chloride solutions and saline solutions. This makes it perfect for saltwater and marine applications. However, be cautious when using these materials with strong acids or oxidizers, such as sulfuric acid, bromine, and phosphoric acid, as they can compromise sensor integrity.

Plastics

Plastic materials are often cost-effective and chemically resistant, but they come with important limitations. Materials such as polypropylene and polyurethane are an excellent option for chemicals such as chloride and sodium hydroxide. They do not, however, play well with halogenated and aromatic hydrocarbons such as fluorine, chlorine, benzene, and toluene. Temperature is also a limiting factor for many plastics, as higher operating temperatures can accelerate material breakdown.

Durable Plastics

For highly aggressive chemical environments, high-performance plastics such as PTFE (polytetrafluoroethylene) or even PVDF (polyvinylidene fluoride) offer broad chemical resistance. These materials typically carry a higher cost  and may not be available for particular sensor types. APG offers a variety of sensors with PVDF bodies, such as submersible pressure sensors, radar level sensors, and float level sensors.

For certain types of acids and chemicals where you’re using an ultrasonic sensor, we recommend considering a sensor that has both a transducer face and mounting threads constructed of PVDF, ensuring all exposed components are protected.

Temperature

Temperature acts as a multiplier when it comes to chemical compatibility. A material may be fine in one temperature range but will break down in another. For example, sensors with stainless steel generally handle high temperatures better than their plastic counterparts.

Checking for Chemical Compatibility

To simplify the evaluation process, take a step-by-step approach:

• Identify the solutions, liquids, and/or vapors that will have contact with your sensor.
• Identify the exposed materials of your potential sensor: transducer face, threads, body, etc.
• Cross-check the compatibility of each interaction, using MSDS sheets, a compatibility database, or other guide.

As you can see, these guidelines are very general and there are plenty of exceptions. We recommend you consult with resources such as our chemical compatibility guide, found right here on APG’s website. Keep in mind that even a reputable resource will almost always recommend you do your own testing before you initiate a full system installation.

If you have questions regarding chemical compatibility, send us an email, give us a call, or Live Chat with us. We have a lot of experience with different chemicals, and we may have a good answer for you. If not, we can walk you through our chemical compatibility guide to help you find a probable match.