Workshops equipped with ozone disinfection equipment, corona surface treatment machines and plasma mold cleaning devices generate high-concentration ozone gas. Ozone is a strong oxidizing agent that continuously corrodes thermocouple metal sheaths, alloy wire cores and plastic cable insulation layers, accelerating irreversible aging and performance degradation. Most factories only focus on high-temperature and corrosion resistance of thermocouples while ignoring ozone oxidation damage, resulting in rapid probe failure within 2–3 months of use near ozone-generating equipment. This article analyzes ozone oxidation damage mechanisms and supporting anti-ozone thermocouple matching and protection schemes.
Ozone destroys thermocouple components through two core oxidation paths. First, metal material oxidative corrosion. High-concentration ozone penetrates tiny gaps of probe sheaths and cable connectors, reacting with chromel-alumel alloy wires, stainless steel springs and sheath surfaces at room temperature without relying on high heat. Ordinary 304 and 316L steel rapidly form thick brittle oxide layers under ozone exposure, developing pitting micro holes within weeks; K-type alloy wire cores suffer uneven oxidation, distorting thermoelectric potential curves and generating stable temperature drift without alarms. Second, polymer insulation aging cracking. Conventional PTFE, PVC and glass fiber outer insulation undergo ozone-induced molecular chain breakage, turning hard and brittle, with surface micro cracks spreading inward continuously. Cracked insulation loses isolation protection, allowing moisture and dust to penetrate and trigger intermittent short-circuit and signal leakage faults. Glass fiber braided sleeves absorb ozone and accelerate fiber pulverization, shedding debris to contaminate cleanroom molds.
First, anti-ozone exclusive thermocouple material selection standards. Sheath material must upgrade to Hastelloy C series alloy, which contains high chromium and molybdenum components forming dense anti-oxidation passivation films to resist strong ozone corrosion; ordinary stainless steel sheaths are completely prohibited for ozone-exposed stations. Thermoelectric alloy wires adopt high-purity vacuum smelting chromel-alumel with anti-oxidation coating on each filament surface to slow ozone erosion of core conductors. Cable outer insulation switches to ozone-stabilized modified PTFE added with anti-ozone carbon black additives, which can resist continuous ozone oxidation for more than 12 months without cracking, replacing ordinary unmodified PTFE and PVC. All spring bayonet parts use fully passivated Hastelloy alloy springs to avoid ozone-induced rust and elastic fatigue attenuation. Hot junctions adopt full vacuum hermetic sealing to block ozone gas from penetrating internal magnesium oxide insulation layers.
Second, physical isolation protection transformation for existing ordinary thermocouples unable to be replaced in batches. Wrap all exposed cable sections with thick aluminum foil airtight tape to form an ozone isolation barrier, and route cables inside fully closed plastic threading pipes to cut off direct ozone contact. Install independent closed isolation partitions around ozone-generating equipment to prevent ozone gas from diffusing to adjacent mold production stations. Adjust mold wiring paths to move thermocouple cables more than 3 meters away from corona treatment and plasma cleaning machines, reducing ozone concentration exposure around probes to safe levels. Cover mold junction boxes with sealed ozone-proof outer casings filled with activated carbon filter cotton to absorb internal residual ozone gas and protect plug pins from oxidation.
Third, standardized daily inspection and maintenance rules for ozone-area thermocouples. Carry out full appearance inspection of probes and cables every two weeks: check sheath surfaces for gray brittle oxide layers and cable insulation for tiny cracks and powder shedding. Wipe connector pins and sheath surfaces with alcohol cloth weekly to remove ozone oxide deposits, and reapply anti-oxidation conductive grease on gold-plated pins to form an isolation film. For molds working near ozone equipment, shorten thermocouple calibration cycle to two months and full replacement cycle to four months, one month earlier than ordinary workshop probes. After daily shutdown, turn off ozone equipment ventilation fans and close isolation partition doors to prevent overnight ozone accumulation accelerating component aging.
Fourth, workshop environmental auxiliary optimization to reduce ozone concentration. Install dedicated ozone exhaust pipelines and activated carbon absorption devices for all ozone-generating machines to discharge and decompose ozone gas in real time before it diffuses into the molding workshop. Adjust equipment working schedules to stagger ozone treatment operations and mass injection production, avoiding simultaneous high-concentration ozone exposure and mold heating operation. Real-time ozone concentration detectors are installed at each production station; once the concentration exceeds the safe threshold, trigger ventilation system automatic startup to dilute ozone gas.
By deploying anti-ozone alloy and insulation thermocouples plus physical gas isolation protection, the aging failure rate of thermocouples near ozone equipment can be reduced by over 90%, eliminating hidden temperature drift and cable short-circuit faults caused by strong oxidizing ozone gas.
