Effect of heat-treatment on the pH sensitivity of stainless-steel electrodes as pH sensors

Abstract

Effect of heat-treatment on the pH sensitivity of uncoated stainless-steel electrodes was investigated to comprehend the pH sensitivity of metal-oxide coated stainless-steel electrodes as novel pH sensors. The pH sensitivity of stainless-steel electrodes as-received and heat-treated at 500 °C, 600 °C and 700 °C for 24 h were 91 %, 94 %, 102 % and 91 %, respectively. The pH sensitivity tended to increase with increasing heat-treatment time at a given temperature. Thus, the most suitable heat-treatment condition for the stainless-steel electrodes was 600 °C for 24 h. The austenite phase (fcc) was the main phase on the surface of the heat-treated stainless-steel electrodes. Unexpectedly, the change in the martensite phase (bcc) as the second phase with heat-treatment temperature was similar to the pH sensitivity, with the martensite phase affecting the pH sensitivity. Therefore, it appeared that the pH sensitivity of the metal-oxide coated stainless-steel electrodes was affected by the underlying stainless-steel as well as the outer metal-oxide film coating. A prototype stainless-steel tube electrode was used as a working electrode for demonstrating the depth profiling of pH. The stainless-steel tube electrode showed good performance for measuring pH depth profiles compared to commercially available glass electrodes.

Ion-Sensitive Stainless Steel Vessel for All-Solid- State pH Sensing System Incorporating pH-Insensitive Diamond Solution Gate Field-Effect Transistors

“…Similar selectivity study should be conducted in the future to understand the limitation of this all-solid-state sensing system with the untreated commercially available stainless steel SUS 304. In addition, surface characterizations including XPS (Xray photoelectron spectroscopy) will help clarifying if there is any difference between the current commercially available stainless steel and others reported in the literatures [1,2]. Fig.…”

“…TAINLESS steel has attracted much attention in the field of biosensing and food industry due to its fast response, low cost, and high sensing capabilities [1][2][3][4][5]. Several studies have reported the use of stainless steel (SUS 304 and SUS 316) for sensing applications and addressed some existing issues of surface.…”

pH, the Fundamentals for Milk and Dairy Processing: A Review

“…RT F ln a inner a outer (24) Glass membrane electrodes are classified as solid electrodes responsive to changes in H + activity and may consist of a combined reference and pH electrode. Compared to colorimetric methods, commercially available glass electrodes give a good linear response in the pH range 2 to 9, with a short pH response time up to pH 14, give good reproducibility, and are durable [38,39]. Glass probes are most suited to laboratory use and given their brittle nature and relatively small operation temperature range, there are limitations when used in the food, beverage and biomedical industry [31].…”

Acid-base potentiometric titration using a stainless steel electrode without oxidative treatment

“…More recent research has tried to elucidate aspects of the response of stainless steel to pH, as the sensing mechanism is not entirely clear. For example, Hashimoto et al [ 17 ] showed that the layer underlying an oxide coating plays a key role in the response; therefore, the oxide-H + double layer interface is not the only one responsible.…”

“…Despite this, there are few studies on the use of the nonoxidised surface of stainless steel as a pH sensor. Research that has performed the evaluation without oxidation has not found a better potentiometric response than when oxidation is performed [ 17 ]. However, this work presents evidence that the nonartificially oxidised surface of an AISI 304 stainless steel electrode can respond in a Nernstian manner to pH.…”