Corrosion and passivation of the 304 stainless steel in formic acid solutions

Abstract

Anodic and cathodic potentiostatic polarization curves for 18Cr–10Ni stainless steel electrodes in aqueous formic acid solutions of various concentrations (2.65; 5.3; 10.6; 15.9; and 21.2 M) have been recorded at room temperature in presence and in absence of the dissolved oxygen. The stainless steel is in active state in all tested solutions and passes in the passive state by anodic polarization, presenting an extended region of stable passivity, which shifts to positive potentials domain with the increase of the formic acid concentration. The corrosion and passivation electrochemical parameters were evaluated as function of formic acid concentration. The solution containing 10.6 M HCOOH was the most aggressive for the stainless steel in the active and in the passive state, presenting the maximum values of the corrosion current, critical current of passivation and passive current densities. The corrosion potentials remain in the active state even after 72 h of immersion in the tested formic acid solution and in the presence of dissolved oxygen. The formic acid oxidation takes place indirectly, in the transpasive region of the anodic curves, presenting the high rate in solutions of mean concentrations.

Effect of heat stable acids on corrosion and stress corrosion cracking initiation of 304 and 316 stainless steels in activated methyl diethanol amine (aMDEA) solution

“…Based on reaction 1, formic acid tends to decompose in solution, forming HCOO ̶ and H + [21]. Then, the HCOO ̶ anion could dissolve the Cr 2 O 3 oxide passive layer according to reaction 2 [21,22]. While passivation potential and break down passive layer's potential are partly same for 304 and 316 steels in aMDEA + formic acid, primary passivation current density ( i P ) is considerably different.…”

“…Then, the HCOO ̶ anion could dissolve the Cr 2 O 3 oxide passive layer according to reaction 2 [21,22].…”

Effect of Formic Acid on Corrosion Behavior of STBA24 Low-Alloyed Steel and Its Weldment in Simulated Boiler Water Containing Chloride Ions

“…It is therefore considered not only Fe-oxides and Cr-oxides, 19) but also iron carbonate (FeCO 3 ) and chromium carbonate (Cr 2 (CO 3 ) 3 ) are easily formed during the OCP measurements in WQ2. 18) These corrosion products adhere to the specimen surfaces; therefore, the film formed became thicker. On the other hand, the quick formation of the thicker film indicates that a certain magnitude of corrosion progressed in WQ2.…”

Effects of paraformic acid supplementation, as an antibiotic replacement, on growth performance, intestinal morphology and gut microbiota of nursery pigs

“…Formic acid has especially been demonstrated to enhance gastric activity [24], gut health [25], immune status [26], and modulate the microbiota [26], leading to improvement of growth performance in nursery pigs. However, formic acid is corrosive [27,28], thus affecting equipment life, creating handling difficulties, and also causing general irritation to workers [29,30]. These disadvantages limit its usage in animal husbandry [17].…”