Correction to: “Cooperativity Between Zirconium Dioxide Nanoparticles and Extreme Pressure Additives in Forming Protective Tribofilms: Toward Enabling Low Viscosity Lubricants”

The SLIM technique reported in this work uses an RGB optical signal to calculate in situ tribofilm thickness. Due to a firmware error in the Spacer Layer Interference Method (SLIM) camera of the Mini-Traction Machine (MTM) used by the authors, the output data of the SLIM system contained an oversaturated blue signal, leading to incorrect film heights in the SLIM system (Fig. 2g). In the course of correcting reported SLIM data with a new, correctly calibrated camera, the authors discovered an error in the White Light Interferometer (WLI), which had originally been obfuscated by the SLIM error: oil residue on the MTM samples led to artifacts in measurements of tribofilm step-edge heights. WLI data obtained after using a modified cleaning procedure avoided this artifact. This WLI artifact changes the morphologies of reported data which contain ZrO2 (Figs. 3, 4) and the estimated wear of the MTM specimens (Fig. 8). Figures 6 and 7 concern control specimens without ZrO2, and are therefore unaffected by the viscous oil error. Though the corrected tribofilm heights and step edges were systematically less than the originally published values, the conclusions of the original work are unchanged. Zirconia tribofilms formed in fully formulated 75W-80 gear oils led to significantly less wear of the steel substrate compared with films formed in neat polyalphaolefins, suggesting cooperation between ZrO2 and the P/S containing co-additives of the gear oil. Accordingly, the following corrections are warranted.