Huahui Chen

Erosion–corrosion of thermal-sprayed nylon coatings

Abstract Thermal-sprayed coatings nylon1010, SiCw-nylon1010 and Al 2 O 3 p-nylon1010 were deposited on 16Mn steel. Erosion–corrosion tests were conducted using an erosion–corrosion tester in pH 1–12 sand slurry with impact velocities from 2.1 m/s to 5.6 m/s. The effects of pH value and impact velocity on the coatings were discussed. The results showed that the coatings presented good erosion–corrosion resistance except both in strong acid and in alkaline slurries. It was found that both SiC whisker and Al 2 O 3 particles added into nylon increased the erosion–corrosion resistance of the nylon coating because they resisted the impact of sand particles. The Al 2 O 3 p-nylon1010 coating had the lowest erosion–corrosion loss rate at low velocity. However, at higher velocity its erosion–corrosion loss rate increased due to the spalling of Al 2 O 3 particles. At all test conditions, the plastic deformation, tearing and the dissolve swelling and hydrolysis of nylon matrix were dominant mechanisms. At higher velocities the partial spalling of Al 2 O 3 particles occurred so that they could not play a reinforcement role. In strong acid or alkaline slurry, the erosion–corrosion resistance of the coatings depended not only on the properties of nylon and reinforcements as well as their bonding but also on the synergetic effects between erosion and corrosion.

Corrosion Behavior of Low Alloy Steels in High-mineralized Mine Water

The corrosion behavior of low alloy steels, such as 27SiMn, 30CrMnSi, 30CrMnTi, 40Cr and Q550 was studied comparatively in high-mineralized coal mine water, tap water and NaCl solu- tion by means of immersion test, salt spray test and electrochemical methods as well as XRD and SEM with EDS. The results showed that elements Cr and Si can significantly affect the corrosion resistance of low alloy steels: in chloride containing media, Si exhibits stronger effect than Cr on the corrosion; whereas in the presence of oxygen (water and gas phase), Cr exhibits stronger effect than Si. Therefore, 30CrMnTi and 40Cr have better corrosion resistance in the coal mine water. The corrosion behavior of the low alloy steels in the coal mine water depend not only on the role of alloying elements but also on the compactness of the formed limescale induced by mineral ions.