Crevice Corrosion of Titanium in High Temperature-Concentrated Chloride Environments

Abstract

Crevice corrosion of titanium is activated in concentrated chloride media at 100°C. This was possible only with the tightest gap (0.005 cm) between Ti-Ti surfaces. No crevice corrosion was observed with greater gap dimensions. The design of the crevice led to the occurrence of two concentric circular rings of corroded areas, with many pits on them. After potentiostating in the passive region for 5 h in 25% NaCl (pH = 4.7)-where hydrogen evolution is thermodynamically prohibited-hydrogen gas bubbles were observed to egress out of the crevice mouth during ongoing crevice corrosion. This indicates that hydrogen evolution occurs within the crevice. The results are compatible with the occurrence of gradually increasing ohmic potential shift and localized acidification in the crevice electrolyte as judged by the measured gradual increase of the crevice corrosion current. The high acidity of the bulk electrolyte does not seem to be sufficient or even a necessary condition for crevice corrosion to occur.

A critical appraisal of laser peening and its impact on hydrogen embrittlement of titanium alloys

“…This acidification can lead to the film breakdown/recrystallization process which takes place when the temperature is raised to >65 °C when crevice corrosion commonly initiates on the most susceptible Ti 2 . 101,102 This is coherent with the industrial guidelines for nullifying crevice corrosion, that is, the temperature <70 °C 40 and outcomes obtained by Shibata and Zhu 103 as shown in Figure 6.…”

“…A study of commercial pure titanium in 1.5% HCl + 19% NaCl at 100 °C with 0.6 pH reveals that the pitting and crevice corrosion occurred on plate surface. 101 Test is performed under potential of −174 mV with saturated calomel electrode at −0.3 mA of current for 12 h of duration. The reason for the occurrence of crevice corrosion is that hydrogen gas bubbles evolve in crevice region and disperse in electrolyte present at the crevice region, which increases the resistivity leading to rise in potential drop.…”

“…Photograph of (a) untreated and (b) pitting and crevice corrosion attacked on crevice surfaces after treating with 1.5% HCl + 19% NaCl at 100 °C. 101 …”

Corrosion of Titanium: Part 1: Aggressive Environments and Main Forms of Degradation

“…Titaniummaysuffercrevicecorrosioninhotchloridesolutions (62).Infact,titaniumcrevicecorrosionishighlytemperature dependent: for commercially pure titanium, it is generallyacceptedthatcrevicecorrosiondoesnottakeplace under70°CregardlessofpH;forpH>10,itoccursregardless Environments and degradation forms e298 oftemperature (30).Attemperatureshigherthan70°C,crevicecorrosionisreportedtohappeninchloride-,bromide-,iodide-,fluoride-orsulfate-containingsolutions(63)onlywith crevicegapssmallerthan50μm (64).…”

“…The same authors (63, 64) have studied the dependence of crevice corrosion initiation on temperature in 0.27 M NaCI. An abrupt increase in crevice corrosion occurrence occurred for temperatures above 75°C.…”