Materials Selection
Materials Selection for Agricultural Applications
- Structural Materials (Greenhouses, Frames, Supports)
- Steel (galvanized, stainless): strength, durability, but risk of corrosion in moist/aggressive soils.
- Aluminum: lightweight, corrosion-resistant, but higher cost.
- Composite FRP: lightweight, non-corrosive, long service life.
- Soil-Contact and Irrigation Systems
- PVC / HDPE / PEX: resistant to soil chemicals and fertilizers, flexible, low cost.
- Stainless steel (316L): for critical fittings and sensors where corrosion resistance is essential.
- Ceramics / porous frits: for reference electrodes, soil moisture probes.
- Storage & Handling (Fertilizers, Chemicals, Water)
- Polyethylene tanks: resistant to acids, alkalis, fertilizers.
- Fiberglass reinforced plastic (FRP): chemical and weather resistance.
- Epoxy-lined steel: where structural strength plus chemical resistance is required.
- Sensor & Electronics Housing
- UV-stabilized polymers (ABS, polycarbonate): protect against sunlight and weathering.
- Encapsulation resins (epoxy/silicone): moisture and chemical sealing.
- Titanium or graphite: as electrodes for electrochemical soil/plant monitoring.
- Wear & Cutting Tools (Plows, Blades, Harvesters)
- Hardened steels: abrasion resistance.
- Carbides / ceramics: for extreme wear surfaces.
- Polymer coatings / composites: reduce friction and soil adhesion.
- Sustainability Considerations
- Recyclability and biodegradability (bio-plastics, natural fibers).
- Life cycle cost vs. initial cost.
- Compatibility with soil, water, and crop systems.
Electrochemical Impedance Spectroscopy
Electrochemical Impedance Spectroscopy (EIS) For Materials and Coating Selection
EIS combined with accelerated environmental exposure tests, such as salt spray (fog) tests, humidity tests and ultraviolet light (QUV) exposure tests, can help to predict the time-to-failure of painted or coated samples and their performance in barrier properties
When used with accelerated environmental exposure tests, EIS acts as a quantitative detector of coatings quality. The organic coatings resistance generally degrades with time. The degradation is associated with corrosive ions and water penetration into the coatings, transport of ions through the coating, and subsequent corrosion reactions at the polymer-metal interface.
Even though an accelerated environmental exposure test with EIS is faster than real- world exposure, it still takes a long time (from hundreds or thousands of hours). Furthermore, in some cases, for instance, high performance durable coatings with high thickness, the failure of coatings can not be achieved after a long time exposure using this method. New technologies, which can rapidly assess high performance durable coatings, have been developed by incorporating new concepts, terminology, theoretical calculation and unique electrochemical setups into traditional EIS testing. The details are described below.
Percentage of Ideal Protection
The new terminology of primary EIS measure used for comparisons between coatings as EIS measurements are made during the course of an environmental exposure is the “percent of ideal protection.” It is used to summarize the changing frequency- dependent impedance of a coating, which reflects both the water penetration and the low frequency impedance which approximates the pore resistance. In traditional EIS measurement, an estimate of the low frequency impedance is given. Therefore, the percentage of ideal protection forms a reliable method of high performance durable coating evaluation and rating.
