Effects of Test Conditions on Corrosion Reactions and Hydrogen Absorption in Hydrogen Embrittlement Tests Using an Ammonium Thiocyanate Solution

Abstract

Ammonium thiocyanate is widely used as a reagent for promoting hydrogen absorption by high-strength steels. The effects of the solution concentration, temperature and dissolved oxygen on corrosion film formation, corrosion reactions and hydrogen absorption were investigated in a hydrogen embrittlement test environment using an ammonium thiocyanate aqueous solution. A still bath of a 20 mass% ammonium thiocyanate solution displayed a supply limitation, whereas a solution with flow influenced the corrosion and hydrogen absorption by the tested steel. The concentration of dissolved oxygen that forms an iron oxide film was found to have a small effect on hydrogen absorption. The change in the hydrogen content of the tested steel with elapsed time is explained in terms of changes in the equilibrium concentration of hydrogen on the steel surface and in the corrosion rate. The change in the solution pH during potentiostatic electrolysis tests in an ammonium thiocyanate solution is also discussed.

Effect of Hydrogen on the Tensile Behavior of Austenitic Stainless Steels 316L Produced by Laser-Powder Bed Fusion

“…The efficiency of this solution in the H permeation was reported several times in the literature [19,[21][22][23][24][25][26][27][28][29]. Ammonium thiocyanate (NH 4 SCN) is widely used as a reagent (hydrogen recombination poison) for promoting hydrogen absorption by steels, and during hydrogen charging, the solution was de-aerated with N 2 [22,30]. Samples were connected to a cathode, and a Pt coil was connected to the anode.…”

Delayed Fracture in Automotive Advanced High Strength Steel: A New Investigation Approach

“…During plant tests, the hydrogen charging of car parts was carried out in an electrochemical cell with impressed cathodic protection current. A plexiglass tank, large enough to contain a sufficient portion of the test pieces, constituted the electrochemical cell and was filled with a solution of distilled water with NaCl (3.5% w/w) and ammonium thiocyanate (0.35% w/w) . The anode was a large grid in AISI 316L and the charging current density was kept between 5 and 10 A m −2 .…”

Effect of Ammonium Thiocyanate on Hydrogen Entry Behavior of Low Alloy Steel under Galvanostatic Cathode Charging

“…7, NH 4 SCN decreased the cathodic current, and the Tafel slopes of cathodic reaction were about − 0.120 V•decade − 1 in acidic condition of pH 3.0. Therefore, it was considered that the dominant cathodic reaction in this study was hydrogen evolution reaction, not reduction of SCN − in Ichiba's 5) study. To determine the mechanism of HER, the Tafel slope or the dependence of surface hydrogen concentration on hydrogen charging current should be obtained.…”

“…A number of studies about the effects of SCN − on hydrogen entry and corrosion behavior have been reported so far. Ichiba et al 5) measured the corrosion rate and the polarization curves of steel bars for prestressed concrete in 0-20 mass% NH 4 The effect that SCN − accelerate hydrogen entry into steel is widely known. Marshakov et al 6) pointed out that SCN − increased hydrogen entry efficiency by using Iyer Pickering Zamanzadeh (IPZ) analysis.…”