In Situ Transmission X-Ray Microscopy of the Lead Sulfate Film Formation on Lead in Sulfuric Acid

Abstract

Transmission X-ray microscopy is utilized to monitor, in real time, the behavior of the PbSO 4 film that is formed on Pb in H 2 SO 4 . Images collected from the synchrotron x-rays are coupled with voltammetric data to study the initial formation, the resulting passivation, and the subsequent reduction of the film. It is concluded with support from quartz-crystal-microbalance experiments that the initial formation of PbSO 4 crystals occurs as a result of acidic corrosion. In addition, the film is shown to coalesce during the early stages of galvanostatic oxidation and to passivate as a result of morphological changes in the existing film. Finally, it is observed that the passivation process results in the formation of large PbSO 4 crystals with low area-to-volume ratios, which are difficult to reduce under both galvanostatic and potentiostatic conditions.

Transmission X-Ray Microscopy of the Galvanostatic Growth of Lead Sulfate on Lead: Impact of Lignosulfonate

“…The transmission X-ray microscopy (TXM) experiments were conducted using the same experimental set-up and procedure outlined in [24]. To study the impact of additives on the mechanisms of PbSO 4 growth, two separate experiments were conducted: one with and one without 26 ppm sodium lignosulfonate (i.e.…”

“…In addition, all images in this work underwent further refinement using ImageJ software in order to better visualize the nucleation and growth of the PbSO 4 films. A more detailed description of the image refinement procedure can be found in [24].…”

“…Additional electrochemical experiments with and without 26 ppm lignin in the electrolyte were performed in order to support the TXM results. Pb electrodes were formed by electroplating a 10-μm thick layer of lead unto a 38-μm thick copper substrate using the same plating procedure outlined in [24]. Prior to plating, the substrate was rinsed with isopropyl alcohol and de-ionized water.…”

“…corr i is the steady state corrosion rate, which for this system is 50 μA cm -2 . [24]. According to Eq.…”

“…In our previous work, transmission X-ray microscopy (TXM), an imaging technique with a fast acquisition time (up to one second per image), was used to study the initial growth, passivation, and reduction of the PbSO 4 film on Pb in H 2 SO 4 [24]. The present study seeks to expand this work by investigating the galvanostatic growth of PbSO 4 in the presence of sodium lignosulfonate, an organic macromolecule which is the precursor to many commercial chemical additives (e.g.…”