TMT rebars in concrete start corroding causing spalling and cracking, and weakening the whole structure. Chloride from various sources penetrates to the rebar and the electrochemical process of corrosion starts. The rust expands up to four times its original volume and creates an internal pressure (about 4000 PSI), which severely damages the concrete.
Rass-O’-Nil® Kover is a one-step polymerised metallic phosphate nano-deposit (less than five microns) with conductive metal ions to give sacrificial protection (cathodic) against corrosion to structural steel during storage, transhipment and inside concrete mortar.
Rass-O’-Nil Kover is applied in a one tank flash-dipping with turbulence or brush or spray coating on cooling bed at 60 degrees temperature.
Complex sacrificial protection through conductive mix metal oxide (ion) deposit to the rebar or structural steel’s micro-structure gives excellent protection from corrosion and improves the bond between concrete and steel. RASS-O’-NIL enriched conductive metal oxide (ion) is in electrical contact with a metal more noble in the electromotive series such as steel, a galvanic cell is established and electric current will flow when an electrolyte contact develops by metallic couple.
RASS-O’-NIL is low cost per linear foot/ tonnage compared epoxy coated or galvanized reinforcing steel. Rass-O’-Nil Kover Technology was tried at Tata Steel under agreement.
RASS-O’-NIL PREVENTS CORROSION IN CONCRETE:
Corrosion occurs when chloride penetrates through defects in a protective (passivating) oxide layer that is normally found on the reinforcing bars. A soluble complex of iron chloride forms and moves away from the bar and deposits expandable insoluble iron oxide in the concrete.
RASS-O’-NIL treatment cathodically blocks the corrosion action of chloride salt by its stabilized passivating deposits and repairs the defects that occur in the oxide structure, preventing chloride ions from penetrating to the pure iron.
Rass-O’-Nil’s healing effect in concrete: cross section of rebar in chloride laden concrete showing the condition of natural passive layer and the effect of natural system.
RASS-O’-NIL treated rebar in concrete after one year without rust.
Steel Treatment, Pickling and Passivation Quality:
The Rass-O’-Nil treated metal surface sealed with a finish coat withstood more than 900 hours of salt spray test, passed the 1.5 kg scratch test, and adhesion test.
Rass-O’-Nil stringently satisfies ASTM B117 (USA) and IS: 13515-1992 (Indian Standard). The Rass-O’-Nil deposit does not come off from the steel even when the metal is bent up to 180°, punched, drilled or heated up to 400° C.
Rass-O’-Nil treated metal surfaces, sealed with a finish coat, left in the open atmospheric conditions for years, do not allow corrosion inside concrete.