Slags from the iron and steel industry may be used in agriculture to correct soil acidity. Current assay assesses the effect of iron and steel industry´s slag, derived from stainless steel, and compares it to limestone as soil acidity corrective and silicon source in coffee plants. The experiment was conducted between December, 2012 and January, 2014 in the municipality of Machado MG Brazil, in a 4-year-old coffee plantation, cultivar Catuaí Amarelo IAC 30. Experimental design comprised randomized blocks in a 2x4 factorial scheme, with control and four replications. Treatments combined two soil acidity correctives, namely, stainless steel slag ("Agrosilício") and limestone; 4 corrective doses corresponding to 0.5; 1; 1.5; 2 times the amount required to raise index base saturation (V%) of the soil´s surface layer (0 to 0.2m) by 60%. Control did not contain any soil correction. Soil samples were collected during the experiment at depths 0 to 0.1m; 0.1 to 0.2m; 0.2 to 0.4m; similarly, samples of coffee leaves, at 180 and 390 days, respectively, after the application of correctives. Stainless steel slag showed the same efficiency as limestone in soil acidity correction at 0 to 0.1m layer, and in providing Ca 2+ to the coffee plant. Stainless steel slag does not correct soil acidity at 0.1 to 0.2 and 0.2 to 0.4 m layers in coffee plants within a 180 day period. Stainless steel slag increases silicon rates in the soil and in the coffee leaves, and increases yield when compared to limestone.