Corrosion and thermal shock behavior of atmospheric plasma spraying coatings on agricultural disc harrows

Abstract

Atmospheric plasma spraying (APS) represents a critical solution for enhancing the durability of agricultural components, such as harrow discs, which are subjected to synergistic wear and corrosion during soil cultivation. This study presents experimental results evaluating the electrochemical corrosion behavior and thermal shock resistance of discs coated via atmospheric plasma thermal spraying. Both metallic and ceramic materials, in powder form, from established manufacturers were used to produce the coatings, and the three types of coatings (two metallic and one ceramic) have the following chemical compositions and trade names: W2C/WC12Co (Metco71NS), Cr2O3-4SiO2-3TiO (Metco136F) and Co25.5Cr10.5Ni7.5W0.5C (Metco45C-NS). The coatings were analyzed using electron microscopy to evaluate the surfaces following corrosion testing. The ceramic coating based on the Cr2O3-4SiO2-3TiO demonstrated the highest protective efficiency by increasing the charge transfer resistance from 307 Ω/cm2 to 2213 Ω/cm2 for the ceramic coating. It provided a superior physical barrier, reducing the corrosion current density from 0.140 mA/cm2 for unprotected substrate to 0.004 mA/cm2, representing an improvement of nearly two orders of magnitude. These findings demonstrate that implementing Cr2O3-4SiO2-3TiO ceramic systems can significantly extend the operational lifespan of soil-engaging components, providing a cost-effective strategy for reducing maintenance intervals and material loss in aggressive agricultural environments.