No abstract

Galvanic type atmospheric corrosion monitoring (ACM) sensors can distinguish wet and dry conditions of a surface by reporting spiked charge when there is an electrolyte film on the sensor. In this study, FeAg type ACM sensor was exposed to monitor time of wetness (TOW ACM ) on carbon steel and weathering steel coupons at seven test stations in Thailand. Climate parameters were monitored by weather stations. Chloride and sulfur dioxide deposition rates were obtained by dry gauze and lead dioxide cylinder methods, respectively. The objective was to investigate the effects of TOW ACM , climate, and aerosols on corrosion rate in Thailand tropical climate under high temperature, high relative humidity, and frequent monsoon-induced rainfalls. Multivariable linear regression model applied on the first-year corrosion rate yielded predictive equations for (1) inland areas-as a function of temperature (T) and relative humidity (RH) and (2) coastal areas-as a function of rainfall (RF) with TOW ACM or chloride (Cl ¹ ) deposition rate. The first corrosion map of Thailand was proposed based on the predictive equations for corrosion rates of carbon steel and weathering steel.

This work studies the effects of Zn/Cu ratio and silicon on the improvement of mechanical properties, tarnish and corrosion resistance of 940 silver alloys. The silver alloys to be investigated are divided into 2 groups. The group 1 alloys are Ag-Cu-Zn alloys. The group 2 alloys are Ag-Cu-Zn-0.02Si alloys. The microstructures of all alloys to be tested look similar and consist of a Ag-rich matrix (α phase) and Cu-rich eutectic structure (α + β phase). The proportion of eutectic structure decreases by increasing Zn/Cu ratio. Increasing Zn/Cu ratio significantly decreases hardness, ultimate tensile strength, but markedly increases elongation. Addition of 0.02wt.- %Si to Ag-Cu-Zn alloys has no effect on hardness and ultimate tensile strength, but decreases elongation. The tarnish and corrosion resistance of Ag-Cu-Zn alloys in 1 % NaCl solution at 298 K significantly increases with increasing Zn/Cu ratio. Addition of silicon also improves tarnish resistance.