Thermocouple what maintenance in precious metals

Ways to improve the service life of the precious metal thermocouple is actually using acid oxidation ability, mainly for precious metals will be high temperature platinum rhodium thermocouple on the surface of the organic matter and can be effective to remove acid dissolved impurities. And the main purpose of the acid pickling is effective on the surface of the electrodes is part of the oxides and organic matter clean. Use after the high temperature alloy thermocouple in sodium borate cleaning after acid pickling. High temperature of the metal electrode on the annealing of thermocouple platinum wire, then to the right place to adjust current, make thermocouple at least very hot one thousand one hundred degrees Celsius. To use block sodium borate in contact with the hot spot on, make the liquid flow down along the electrode and sodium borate dispatch current is small, only after the end of the cleaning is done after shut down the power supply, will take off, flow of sodium borate in the beaker on the dedicated with distilled water to the boil, is more than several times, until eventually fully diluted boric acid salt out.

the cleaning method of boric acid sodium is actually in order to adjust the metal or oxide of insoluble in hydrochloric acid. Because sodium borate under high temperature, there will be a serious, melting and melt sodium borate will directly and high temperature in the precious metal thermocouple electrode metal impurity, boron and metal oxide to produce a glass solution, but will follow the hot electrode run together, so that it can effectively remove the dirt from the external electrode. And the purpose of annealing is to fast to get rid of the electrode in the extra stress, effectively improve the high temperature stability performance of noble metal thermocouple. Only reach the appropriate annealing time and temperature can reach the purpose of cleaning.