The nodular cast iron manhole cover is mainly made of nodular cast iron, and the quality of this manhole cover is related to the spheroidization rate. The common coating used to treat castings is antirust asphalt paint. Of course, the surface of nodular cast iron manhole cover is also treated by spraying antirust asphalt paint. Ductile iron manhole cover has an advantage, that is, because of its high strength and good toughness. Municipal roads, highways, communications, electricity, tap water, residential areas, schools and other parks. Municipal Road,Well Cover,Water Grate,Well Cover Frame Baizhu Network Technology Co., Ltd. , https://www.baizhunet.com
[ Method 2] After degreasing, it was immersed in the following solution at room temperature for 2-4 minutes : hydrochloric acid ( 37% ) 10-20 water  90-80 washed with warm water, washed with distilled water, at 66
[ Method 3] in the following solution
[ Method 1] Common solvents for degreasing: trichloroethylene, acetone, methyl ethyl ketone, ethyl acetate, and gasoline. -71 °C Dry for 30 min . 38 ° C Immersed 3-6min: sulfuric acid (d-1.84) 2 1 Water 8 weight sodium chromium by cold water, distilled water, in 40 ° C Dry down.