The degradation mechanism of an epoxy-phenolic can coating

Abstract

Paint remains a widely employed approach to corrosion control due its relatively low cost and proven efficacy. Nonetheless, the processes governing long-term deterioration of intact organic coatings (in the absence of defects) are not fully understood. In this contribution, we investigate the degradation mechanism of a corrosion resistant epoxyphenolic can coating. In-situ time-resolved ATR FTIR is applied to monitor both the chemical integrity of the coating and water uptake as a function of immersion time in water or electrolyte. Ion transport is assessed across free standing films, and morphological changes accompanying immersion are examined using ex-situ advanced scanning probe microscopy techniques. Coatings are found to deform as a result of water sorption during immersion in electrolyte or water, yielding regions of heterogeneous hydrophilicity, yet no change in functional group chemistry is found to occur.  Non-Fickian water sorption is associated with deformation of the coating. HIGHLIGHTS AFM-IR is used to show that hydrophilic pores form during immersion.3

Spectroscopic insights into adhesion failure at the buried epoxy‐metal interphase using AFM‐IR

“…Absorbance of infrared radiation induces abrupt thermal expansion of the sample, and this is detected by deflection of an AFM probe in contact with the surface, Figure 1. Further details of the AFM‐IR technique may be found in our previous publications where we have shown that AFM‐IR spectra obtained using this method closely match to those obtained by conventional FTIR techniques 14–17 . For the present study, AFM‐IR height images were collected in contact mode at a scan rate of 1 Hz using a gold‐coated silicon nitride probe (0.07–0.4 N/m spring constant, 13 ± 4 kHz resonant frequency, Bruker).…”

Reflectance in AFM-IR: Implications for Interpretation and Remote Analysis of the Buried Interface

“… 15 , 40 , 43 , 44 Furthermore, since the IR pulse (10 ns duration), thermal expansion, and damping down of the induced oscillation occur on a faster time scale than the feedback electronics of the AFM, simultaneous contact-mode topographical measurement and IR absorption mapping can be performed at a given wavelength. 8 , 45 − 47 For the present study, AFM-IR images were collected in a contact mode at a scan rate of 0.04 Hz using a gold-coated silicon nitride probe (0.07–0.4 N/m spring constant, 13 ± 4 kHz resonant frequency, Bruker). Maps were obtained using 32 co-averages for 600 points per 300 scan lines.…”

Long-Term Atmospheric Aging and Corrosion of Epoxy Primer-Coated Aluminum Alloy in Coastal Environments

“…To prevent damage to the aluminum alloys used in aircraft structures due to corrosion, a double-layer protection system consisting of epoxy primers along with an anodized film of sulfuric acid has been used as a protection measure [1,2]. Because aircraft are on the ground for most of the time, the main corrosive environment for them is the ground atmosphere, where the coastal atmosphere has the most significant impact on the safety of the structure of aircraft [3][4][5][6].…”