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55 NACE INTERNATIONAL: VOL. 56, NO. 11 MATERIALS PERFORMANCE NOVEMBER 2017 For the OS-2 study, the corrosion inhibi- tor was applied at the end of five wet/dry cycles to the surface of five of the corroding slabs, which were labeled as "treated." At this point in the testing phase, the macrocell current was ~7,000 C in the slabs, indicating corrosion activity was ongoing in all the slabs. The study continued for an additional 13 cycles (18 cycles total). At the conclusion of the 18-cycle testing, all five control slabs showed severe cracking, while only one of the treated slabs showed minor cracking. At the end of five cycles, the average chloride levels at the rebar depth for all the slabs was 1,400 ppm. At the end of 18 cycles, the amount of chlorides for the untreated slabs had increased to 2,450 ppm whereas chloride levels for the treated samples had only increased to 1,850 ppm. Therefore, OS-2 was effective at reducing the rate of chloride intrusion into the concrete. Figure 3 shows the integrated macrocell currents after the OS-2 treatment. Cycle 0 in the graph represents the point at which five slabs were treated with OS-2. The chart shows that after treatment, the integrated macrocell current in the control slabs increased at a much faster rate compared to treated slabs. At the end of the test, crack length and area were measured. The total cracking on the surface was reduced by a factor of four for the treated vs. untreated slabs. 9 Corrosion of the rebar was determined when it was removed from the slabs after cutting open the concrete at the end of 18 cycles. Visual corrosion was 20% higher for the rebar in the control slabs compared to rebar in the treated slabs. 9 Since the slabs were already showing signs of corrosion before treatment, it can be assumed that most of the corrosion obser ved on the rebar from the treated slabs occurred prior to treatment. Carbonation Test Results for OS-1 Carbonation-induced corrosion activ- ity, as monitored by measuring macrocell corrosion, is presented in Figure 4. When comparing treated and untreated samples, the OS-1 treatment was effective in mitigat- ing carbonation corrosion in corroding beams, at corrosion initiation, and when applied at later times. FIGURE 2 Average integrated current after OS-1 treatment. FIGURE 3 Average integrated current after OS-2 treatment. Conclusions The results of the test program show that both organofunctional silanes studied (OS-1 and OS-2) are effective topical sur- face treatments for mitigating severe chlo- ride-induced corrosion in reinforced con- c r e t e d e c k s . T h e c o r r o s i o n a c t i v i t y significantly decreased for slabs topically treated with OS-1 and OS-2 as measured by : • Reduced macrocell corrosion • Mo r e e l e c t r o p o s i t i v e c o r r o s i o n p ot enti al s w ith reduction in th e steepness of the contour maps • Reduced cracking • Reduced corrosion area OS-1 as a topical treatment was shown to also reduce corrosion activity in carbon- ated concrete. The reduction in corrosion was rapid, whether the carbonation corro- si o n h a d j u st i n it i a t e d o r w a s i n a n advanced state. Acknowledgments The authors wish to thank Evonik Corp. for sponsoring the work, and the laboratory personnel at Tourney Consulting Group for their assistance in producing the speci- mens and in testing. Organofunctional Silane Corrosion Inhibitor Surface Treatment Protects Concrete