The object of precleaning is to remove large excesses of soil, especially deposits of solid particles, such as pigmented drawing and buffing compounds. The types of precleaners are solvent, emulsifiable solvent, spray or soak emulsion, soap/detergent soak, alkaline spray, and alkaline soak.
The intermediate cleaning removes residual soils softened or conditioned by precleaning. This is usually accomplished by soak or spray cleaning. For soak cleaning 30 or 120 g/l of alkaline cleaner at 82oC up to boiling for 3 to 15 min in generally used. A typical soak cleaner for steel would contain:
- Sodium dydroxide ------------------- 35% wt
- Anhydrous sodium metasilicate --- 25% wt
- Sodium carbonate ----------------.--- 22% wt
- Sodium tripolyphosphate -------..--- 12% wt
- Anionic surfactant -----------------.--- 5% wt
- Nonionic surfactant ------------------- 1% wt
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