The bottom part of the cast iron surface plate should be treated with the thorough cleaning process. And you should paint it with red anti-rust paint or coatings. Also, the side surface needs cleaning process prior to the rough processing. After the leveling, it should be coated with blue, green, or yellow paint.
The cleaning process could be manually or mechanically accomplished. The manual cleaning process requires low cost but some parts can't be cleaned completely. Instead, the mechanical cleaning process can make the cast iron surface plate ultra clean, though it costs much more.
The cleaning process should be implemented in the natural environment temperature, which is claimed to be the optimum operating temperature. In general, the manual cleaning is carried out in the workshop, and it needs no special requirements. Differently, the mechanical cleaning process is much more complicated. Here below is the detailed relevant introduction.