RPR gives a surface cleanliness which depends on the condition of the surface to be treated and the type and condition of the coating to be removed. RPR will in most cases also clean the pores of the steel and even corrosion pittings. A heavily corroded surface, with a lot of rust, will usually give a lesser grade of cleanliness than a surface with little rust and still mostly covered with coating.
When removing materials with thermoplastic properties, like chlorinated rubber or bituminous coatings, heat transfer from the steel will soften and even melt the underside of the coating.
During the removal process, this slight “melt back” will often cause tiny paint particles to flow back into the pores and re-cure.
These particles can subsequently not be removed by scraping and will show up as a very thin, visible residue, almost like a form of discolouration. If necessary, this residue can easily and quickly be removed by a dry or wet sweep blast (both with very low abrasive consumption) or by water jetting.
RPR will give a visual grade of cleanliness in the range of commercial to near-white blast.
- SSPC – SP 6 to SP 10
- NACE # 3 to # 2
- ISO Sa 2 to Sa 2,5