The hydrogen absorption process for conducting hydrogen embrittlement tests is either immersion in a solution of ammonium thiocyanate or electrochemical reaction. Hydrogen entry into steel was measured to investigate these hydrogen absorption processes by using an electrochemical method. The hydrogen entry into steel caused by an electrochemical reaction in an alkali solution is at the same level of that caused by immersion in an ammonium thiocyanate solution. The electrochemical reaction in an alkali solution enables steel to absorb hydrogen without changing the steel surface condition.
A ring which was part of high-pressure equipment, made from medium carbon 4.5% Cr tool steel with a tensile strength of 2100 MPa was fractured after short-term operation in water. The equipment was used for synthesizing a hard substance, and the ring was anodically polarized at 3 V during the operation. The anodic polarization of the failed ring was attributed to the 6 V DC current applied to the equipment for supplying reaction heat. The surface of the failed ring in water became the anode of the 3 V cell. Delayed fracture tests in water were conducted using bent-beam specimens without notches to investigate the effects of anodic polarization on fracture susceptibility. We confirmed that the fracture time under 3 V was shorter than that at natural potential, showing good agreement with the actual fracture time of the ring. Therefore, we recommended that the surface of the ring be protected from water with a plastic film to prevent the occurence of delayed fracture due to anodic polarization.
In activated sludge treatment facilities, the waste water is purified by microbial metabolic processes. In order to understand the corrosion of SUS304 stainless steels in this facilities, investigation by microbial analysis and electrochemical measurements was conducted. Aerobic bacteria were detected in corroded weld parts. Open circuit potentials (Eoc) of corroded facilities were more noble than that of the stainless steel in controlled waste water and that of no corrosion facilities. Repassivation potentials for crevice corrosion (ER,CREV) of the SUS304 stainless steel were measured in the laboratory and a Eoc > ER,CREV relation was confirmed. It was considered that the cause of the corrosion was the increase of the potential of SUS304 stainless steels by microorganisms action and a formation of crevice by biofilm.
It is attracted that cathodic protection method (CP) is effective in the remedy of rusted rebars, regardless of amount of salt in concrete. The aluminum galvanic anode is one of CP. Rebar potential, current density and temperature were measured at concrete rail way bridge with aluminum panel. Analysis and discussion were given to the effect by temperature shift for rebars potential, neither incident affected for depolarization by it. And, measuring time with off potential for measuring of depolarization was appropriate time.
In hot spring facilities in Kusatsu, Gunma Prefecture, in about two months, SUS304 stainless steel handrails corroded and dissolved uniformly in acid sulfate-chloride spring water containing hydrogen sulfide. Corroded samples were analyzed, remaining handrails were observed closely, an immersion test was conducted at the sources of springs, and corrosion potentials were measured. The result showed that the causes of the corrosion were low pH (pH 2 or less) and the corrosion action of free hydrogen sulfide. Because the handrails corroded in only the type of spring water containing hydrogen sulfide at the two sources of springs with a pH of 2 or less, hydrogen sulfide had a particularly significant impact on the corrosion and accelerated the active dissolution of SUS304 stainless steel. As a measure against corrosion, titanium instead of SUS304 stainless steel was used for handrails. Rusting or local corrosion was not observed about 18 months after use.
To ensure the safety of steel structures that can exhibit fatal damage due to corrosion, it is important to quantitatively clarify the corrosion environment in each member and to evaluate the time-dependent corrosion behavior. The purpose of this research is to propose a method for predicting the time-dependent mean corrosion depth of uncoated structural steel plates subjected to rainfall effect, using an ACM type corrosion sensor consisting of a Fe/Ag galvanic couple. Atmospheric exposure tests were carried out on the uncoated steel plates. In addition, the corrosion environments of the skyward- and groundward-facing surfaces of the specimens were monitored using ACM sensors to evaluate the quantitative relationship between the corrosivity of the atmospheric environments and the mean corrosion depth.