The abrasives are processed chemically with acids and water damp to obtain wanted size, shape, and purity. SiC is washed with alkali or acid to remove adhesions of silicon, metals, metal compounds, graphite, dust, and SiO2 [LIET08].
Diamonds undergo an etching process to roughen their surface [MARI04]. Some abrasives like white corundum undergo special treatments only for marketing aspects, such as washing with acid to remove remaining particles from crushing processes. These remainings would otherwise lead to unwanted grinding tool discoloration.
Electrostatic methods separate sharp-edged grit shapes from blocky grits [MARI07, p. 79].
Grit coatings are either non-metallic or metallic coatings; the first ones being mostly applied to conventional grits.
Grit coatings based on silane (SiH4) are applied onto conventional grits to enhance retention in resin bonds and to resist interactions with the cooling lubricant [KLOC05a, p. 25, JACK11, p. 27, WASH12b, UAMA09]. Silane coating includes mixing of grits and silane solution, then the silane treated grits are cured [SETH11]. Dispersed silicon dioxide is either mixed directly with the grits or applied to the grits in a suspension [KUNZ91].
Red iron oxide coatings are ceramically bonded to the grit in an electronically controlled high temperature heat treatment [WASH12b]. Red iron oxide coatings protect grit surface areas and link well with resin or rubber bonds [JACK11, p. 27, WASH12b]. Corundum grits for cutoff wheels are sometimes coated with red iron oxide [MARI07, p. 79].
Ceramic coatings based on Al2O3 basis are also available for phenolic resin bonded tools [FACT12]. Their advantage is the high coating hardness.