Components used really in industries such as mechanical, chemical, mining and petroleum industries, are often exposed to corrosive and erosive liquid–solid two–phase flow environments. These environments lead not only to high costs maintaining these components but also to shortening their service life. The behaviors of metal materials under corrosive and erosive conditions as well as the related mechanisms have been researched for several years. For reducing material failure caused by erosion–corrosion at surfaces of components, surface modification technology such as plating an Ni–P or Ni–Cu–P alloy coating with a high hardness and good corrosion resistance is an effective method. The behaviors of electroless Ni–P and Ni–Cu–P coatings, J4 and also 316L stainless steel as a contrast material were systematically investigated in liquid–solid two–phase flow (20% H₂SO₄+20 g/L Al₂O₃) by mass loss tst method at different temperatures (25 and 50 ℃) and different erosion rates (0.63—1.88 m/s). The sample surface morphologies and chemical compositions were also observed by SEM. Their erosion corrosion mechanisms were also explained. The results show that their erosion corrosion resistance performance under the test conditions is in the order of plated Ni–Cu–P coating, plated Ni–P coating, plated Ni–Cu–P coating after heat treatment, 316L stainless steel and J4 stainless steel. Their erosion corrosion resistance decreases with the increase of temperature of two–phase flow. Comparing to plated Ni–Cu–P coating, plated Ni–P coating and plated Ni–Cu–P coating after heat treatment, stainless steel 316L has over 8.5, 8 and 2.6 times higher erosion–corrosion rate at 25 ℃and over 392, 80 and 14.8 times higher erosion–corrosion rate at 50 ℃, respectively. The erosion–corrosion rate of J4 stainless steel is ver 28 times at 25 ℃and 13 times at 50 ℃higher than that of 316L stainless steel, respectively. The main corrosion characteristic of J4 stainless steel is selectie corrosion at 25 ℃and uniform corrosion at 50 ℃. However, it is slightly selective corrosion fr 316L stainless steel and uniform corrosion for Ni–P and Ni–Cu–P coatings. The results could be used as a useful reference for the application of electroless plating Ni–P and Ni–Cu–P coatings in erosion–corrosion environment.