**7. Conclusions**

The following conclusions may be drawn from the material presented herein.

1. The development of reinforcement corrosion after initiation can be represented by a relatively fast increase to *csc* followed by a slow rate of corrosion defined by *rsc*, where *csc* depends on the aggregate-cement ratio and water-cement ratio of the concrete and *rsc* is about 0.015 mm/y of the general corrosion for most concrete mixes. Concretes with extremely low permeability are associated with very low values of *rsc*.

2. For aggregate-cement ratios less than about 4, the parameter *csc* increases with the aggregate-cement ratio but decreases for higher aggregate/cement ratios, in both cases more so for higher water-cement ratios. This is attributed to the effect of the water-cement ratio on concrete permeability.

3. The slow loss of the low solubility concrete alkali calcium hydroxide leads, for extended exposures, to a much reduced concrete pH and to a porous concrete matrix that permits the entry of atmospheric or dissolved oxygen, which then causes oxidation of the revealed reinforcement bars. Since the solubility of calcium hydroxide is accelerated in the presence of seawater, corrosion will likely occur earlier for otherwise similar conditions.

4. In some conditions, severe corrosion may occur at deep hairline cracks intersecting the reinforcement and in the presence of chlorides, without necessarily leaving "tell-tale" rust stains. The process involves water-soluble ferrous chloride formed in corrosion pits leaching to the external environment, eventually leaving a characteristic tunneling type of corroded bar. Empirical data show that for seawater with an average water temperature in the range of 10–20 ◦C, the corresponding rate of corrosion *ra* is in the range of 0.22–0.27 mm/y.

**Funding:** This research received no external funding.

**Data Availability Statement:** All data used and described in this study are in the public domain and in the open literature.

**Acknowledgments:** The author acknowledges his colleagues at The University of Newcastle in supporting this research and, through laboratory facilities and technical staff, permitting the continued exploration of the practical aspects of the nature of reinforcement corrosion. The author acknowledges the encouragemen<sup>t</sup> of Joost Gulikers, Rijkswaterstaat (Ministry of Infrastructure and Water Management), the Netherlands, that led to an earlier (2019) version of this manuscript.

**Conflicts of Interest:** There are no conflicts of interest.
