Different modes of corrosion are possible for metal films in contact with liquid solutions, depending on the metal or alloy present, the composition of the solution and conditions such as temperature and mechanical stress [1]. The difficulty of monitoring corrosion processes with good spatial and temporal resolution under a liquid layer creates a challenge for understanding key aspects of these corrosion processes, such as the nucleation sites and growth rates of individual pits during localized corrosion. However, structural changes and chemical processes at the solid/liquid interface can be probed by means of liquid cell transmission electron microscopy under electrochemical control (EC-TEM) [2]. This technique can provide a combination of electrochemical and temporally and spatially resolved data that has already yielded information on corrosion kinetics in liquid solutions [3]. Here, we use EC-TEM to examine galvanic dissolution processes of metal thin films, such as Cu and Ni, by exposure to ppm levels of chemical additives, typically Pd ions, in acidic solutions. We have examined the kinetics of these processes under conditions of different pH and Pd ion concentration, and will also discuss temperature-dependent corrosion reactions in these materials systems.The experiments were carried out in a JEOL 2010F TEM operated at 200 kV using a continuous flow LC-TEM holder (Hummingbird Scientific Co., Ltd) with capabilities for mixing or exchanging solutions, as well as heating and electrochemical control. Metal films were deposited to thicknesses of 20-100 nm by electron beam evaporation. The films were deposited either over blank window chips or over commercially available heater chips that included an electrically isolated resistance heater built into the window. Patterning using either lithography or a stencil mask ensured that the metal film partially covered the liquid cell window to provide an open reference area for imaging during dissolution. After assembling the liquid cell, deionized water was introduced to remove air bubbles inside the cell. The metal film was imaged in water, then either deionized water continued to flow or a solution containing an acid electrolyte (H2SO4) and/or ppm levels of chemical additives (for example, PdSO4) was introduced. The film morphology was then imaged at regular intervals. The resulting structural changes were followed as a function of both the solution chemistry and the illumination conditions. The electron beam is well known to cause radiolysis of water that changes the solution chemistry, for example typically lowering the pH [4]. Unsurprisingly, both the solution pH and the beam intensity affect the rate and morphology of dissolution [5]. Figure 1 shows examples of galvanic dissolution of Cu in 0.1M H2SO4 + ppm level of PdSO4 and dissolution of Ni at lower electron beam flux. Experiments such as these provide information on the spatial distribution of the corrosion process (for example, distinguishing grain boundary pitting from intragranular pitting, and measurin...