Corrosion penetration profiles

Fig. 4 Corrosion inside a pipe (bore 100 mm, wall thickness 6.3 mm), projection technique at 160 kV (double wall penetration), profile plot with calibrated wall thickness loss...

As a final application of the profiling technique, the sensor for large depth measurements described in Section 2.4.2.5 was used to resolve multi-layer polymer coatings on concrete samples. Such coatings are used to protect concrete from degradation and corrosion. They are applied to the concrete surface to reduce the porosity in the upper first millimeters to prevent the penetration of water and... 

SAFETY PROFILE Chromate salts are suspected human carcinogens producing tumors of the lungs, nasal cavity, and paranasal sinus. Chromic acid and its salts have a corrosive action on the skin and mucous membranes. The lesions are confined to the exposed parts, affecting chiefly the skin of the hands and forearms and the mucous membranes of the nasal septum. The characteristic lesion is a deep, penetrating ulcer, which, for the most part, does not tend to suppurate, and which is slow in healing. Small ulcers, about the size of a matchhead, may be found, chiefly around the base of the nails, on the... 

Convective mass transport from small cavities is relevant to through-mask electrodeposition and to localized corrosion and has hence received much attention. In localized corrosion, mass transport is important for determination of the local environment inside an active pit. For through-mask deposition, an understanding of mass transport may be important for design of mixing methods or for analysis of measured deposit profiles. The electrodeposition in circular or rectangular cavities formed by a photoresist has been studied by Kondo etal. it was found that the shapes of deposited bumps can be explained by calculations of vortex evolution and penetration flow. 

The important questions from chloride measurement is how much of the rebar is depassivated and how will this progress Points (a) to (c) in Section 3.2.3 review how the corrosivity of the chloride can change. If chlorides have been transported in from outside then the chloride profile can be used along with measurements (or estimates) of the diffusion constant to estimate future penetration rates and the build up of chloride at rebar depth. 

The drilling mode has also been reported to be preferable for samples potentially affected by supeiicial corrosion effect, as the line profiling mode typically penetrates less into the sample [70]. 

Chloride content. Samples for determining the chloride level in concrete are collected in the form of powder produced by drilling or by the extraction of cores, sections of which are subsequently crushed. The latter method can provide a more accurate chloride concentration depth profile. The chloride ion concentration, used as a measure of the risk of corrosion damage and degree of chloride penetration, is subsequently determined by potentiometric titration. Two distinctions are made in chloride ion concentration testing Acid-soluble chloride content (ASTM C 114) refers to the total chloride ion content, while the water-soluble content represents a lower value. 

Examples of contrasting highly undesirable and favorable ZRA monitoring profiles are presented schematically in Fig. 6.32. In case A, the ZRA sensor response indicates that the HAZ is subject to intense preferential anodic dissolution. Both the weld metal and the parent plate are more noble (cathodic) than the HAZ. The narrow HAZ surrounded by the weld metal and the large parent plate produces an extremely unfavorable galvanic area effect. These conditions lead to weld failure by extremely rapid preferential penetration of the weldment along the HAZ. Actual HAZ corrosion rates could well exceed the values measured with the sensor, as the most severe area effect cannot be repro-... 

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