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© 2012 by Proceq SA

4.10 Evaluation

Typically, two criteria must be considered for the evaluation. (This is merely a guideline. The actual 
evaluation should be carried out by a corrosion engineer.)
1. 

Active corrosion can be expected at locations where a negative potential is surrounded by 
increasingly positive potentials, i.e. locations with a positive potential gradient. Potential dif-
ferences with delta of 100mV within a 1m measurement area, together with negative 
potentials are a clear indication of active corrosion. 

2. 

In order to plan corrective maintenance it is necessary to draw a border between areas of 
active corrosion (anodes) and passive areas (cathodes) within the surfaces showing potential 
gradients. In order to do this it is necessary to set a threshold potential that defines the inter-
section between the two states. ProVista has functionality which aids in this. (Read section 6 
for details).

4.10.1  Example of a typical distribution

If the surface under test has both actively corroding as well as passive rebars, then the two states 
exhibit differing statistical distributions of the potential. In the graphical representations provided 
by ProVista there are typically three characteristic sections (Fig. 4.2). A flattening out of the section 
shows that in these value ranges, there is less data available, i.e. the boundaries of the distribution 
are here.

Fig. 4.2 Example of a relative frequency chart and cumulative frequency chart.

The potential ranges of active corrosion and passivity overlap.
The red cursor (leftmost) = minimum of the passive distribution. 
The yellow cursor (rightmost) = maximum of the active distribution.
Active corrosion is practically certain in the region of the left hand (more negative) straight section. 
Once these cursor lines have been set, the surfaces in this potential range will be automatically 
displayed in the corresponding colour in the CANIN ProVista “Chipping Plot”. 
In the example the red cursor line marks this threshold. A typical “Chipping Plot” taken from a practi-
cal example is shown below.

Summary of Contents for canin+

Page 1: ...canin more than 50 years of know how you can measure Made in Switzerland Operating Instructions Corrosion Analyzing Instrument...

Page 2: ...robe to the indicating device 8 3 3 Power ON and select the correct operating mode 9 3 4 Functional check of the equipment 10 4 Real Tests Potential Measurements 10 4 1 Planning and preparation 11 4 2...

Page 3: ...uency 27 6 12 Chipping graph 28 6 13 Annotations 28 7 Measuring the electrical resistivity 29 7 1 Preparing the concrete surface for measurement 29 7 2 Reading the display screen 30 7 3 Measuring with...

Page 4: ...correct Proceq SA makes no warranties and excludes all liability as to the completeness and or accuracy of the information 1 3 Safety Instructions The equipment is not allowed to be operated by childr...

Page 5: ...they form hydroxide OH with the generally available water and oxygen This principle creates a potential difference that can be measured by the half cell method The basic idea of the potential field m...

Page 6: ...ments Electrical resistivity of the concrete cover Measure with the Wenner Probe This topic is dealt with in detail in section 2 4 Oxygen content at the reinforcement With decreasing oxygen concentrat...

Page 7: ...rate of cor rosion decreases 2 5 Influence of Rebars on Electrical Resisitivity Measurements The presence of rebars disturbs electrical resisitivity measurements as they conduct current much better th...

Page 8: ...lphate with 100 units by weight of distilled water In order to ensure that the solution remains saturated add an additional teaspoonful of copper sulphate crystals into the electrode The electrode sho...

Page 9: ...For potential measurements the instrument must be in Corrosion analys ing mode Switch between modes by pressing MENU place the cursor at Wenner Probe press START select OFF for Corrosion Analysing mo...

Page 10: ...ect measurement on the concrete surface possible Yes No Can the influence from surface coatings be estimated and compensated Yes No Remove the surface coating 4 8 4 9 Pre moisten the surface if requir...

Page 11: ...y be used For more accessible horizontal vertical or overhead surfaces it is much faster to use the 1 Wheel Electrode For large horizontal surfaces the 4 Wheel Electrode is recommended for the reason...

Page 12: ...often used for example on the walls and ceiling of underground car parks however this can cause a small shift of the potentials It is always necessary to check whether or not a measurement can be mad...

Page 13: ...ry The number of pages that are still available for use is shown in the top right hand corner of the measuring screen Fig 5 1 e g 491 P indicates 491 pages are still available The number of pages cont...

Page 14: ...the measurement it should be possible to see a wet patch when applied on dry con crete If this is not the case then the foam rubber plug should be moistened with water again The simplest way to procee...

Page 15: ...ista i Note The nozzle 1 mm is fit as standard On dry surfaces the felt hoop should leave a clearly visible trace as you measure Depending on the character of the concrete it may be necessary to incre...

Page 16: ...Example of a typical distribution If the surface under test has both actively corroding as well as passive rebars then the two states exhibit differing statistical distributions of the potential In t...

Page 17: ...using a small grid is recommended to deter mine the actual Hotspot local potential minimum 5 General Settings 5 1 Backlight The display has a back light which can be switched on or off by pressing the...

Page 18: ...U END MENU START MENU END OFF ON END END START Main menu for resistivity measuring Pressing MENU saves the settings and takes you to the next higher menu Pressing END saves the settings and takes you...

Page 19: ...Pressing MENU saves the settings and takes you to the next higher menu Pressing END saves the settings and takes you to the measuring screen Use the and to select navigate and adjust settings Fig 5 2...

Page 20: ...alue has stabilized If automatic measuring is not selected then values have to be acquired by pressing the START button In both cases values between 200 and 50mV have to be acquired by pressing the ST...

Page 21: ...hese graphs can be inserted in an assessment report and serve the corrosion engineer together with results of non destructive and destructive tests like concrete cover depth carbonation depth chloride...

Page 22: ...Output Fig 5 2 in the Canin display device and press START Click on VistaTransfer button to start the download programme A dialog box appears see Fig 6 2 Select the respective COM port All the object...

Page 23: ...It may be that the objects from a com plete site were not all measured in the same direction See 4 9 3 ProVista allows this to be corrected Select the correct orientation and press OK again to display...

Page 24: ...ion Click on Configuration to alter the appearance and the language of the potential map Fig 6 5 Configuration Window The number range to which the colours are assigned can be changed through varying...

Page 25: ...le button and select the file you wish to add If the file is valid the next screen Fig 6 6 will allow the file to be correctly positioned The new file may be rotated or mirrored to match its orientati...

Page 26: ...ific value 6 9 Additional Functions Save File to save your changes Print View prints the currently visible section of the potential map respectively chipping graph Print File prints the entire measure...

Page 27: ...iagram 6 11 Cumulative frequency Fig 6 9 Cumulative frequency diagram Following an evaluation See 4 10 the corrosion engineer can place the 3 cursors in such a way that they represent areas of differe...

Page 28: ...ture like measured chloride content cracks or other defects can be placed directly in the potential map or the chipping graph The information will be printed and shown in bitmaps By default they are c...

Page 29: ...mmended that annotations within one file be added at different dimension levels i e zoom levels 7 Measuring the electrical resistivity Fig 7 1 Wenner four point probe with cable and control plate The...

Page 30: ...same location moving the probe a few mm between each measurement and taking a median from the 5 values The well moistened probe should be pressed lightly against the surface of the concrete until the...

Page 31: ...f the indicating device In case your PC hardware doesn t support serial ports you can use the USB converter part no 390 00 542 Preparing the PC for the Data Transfer Create directory C PROCEQ Windows...

Page 32: ...surements 980 pages 240 measurements each organised in up to 71 objects and 5 800 resistivity measurements 24 object files tables 256 measurements each Data Output RS 232 interface with USB adapter Ba...

Page 33: ...trode cable 1 5m 4 9 ft cable coil 25m 82 ft CANIN ProVista PC software on memory stick bottle with copper sul phate 250g 330 00 205 Canin Configuration with Rod and Wheel Electrodes Basic equipment s...

Page 34: ...5 Cable clip for telescopic extension 380 02 508 S Foam pad to resistance probe set of 4 pcs 11 Maintenance and Support 11 1 Functional check of the electrodes Correct function can be checked by use o...

Page 35: ...wooden plug facing upwards 11 4 Functional check of the resistivity probe See section 5 5 Assure that the Device Constant shown on the Indicating Device corresponds to the code engraved on the probe...

Page 36: ...asia proceq com Proceq Rus LLC Ul Optikov 4 korp 2 lit A Office 412 197374 St Petersburg Russia Phone Fax 7 812 448 35 00 info russia proceq com Proceq Middle East P O Box 8365 SAIF Zone Sharjah Unite...

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