Preface:
Due to the increasing progress of non-destructive ultrasonic tests, currently one of the most accurate and advanced methods of monitoring the extent and depth of corrosion in industries is the Phased Array method.

Applied techniques in PHASED ARRAY corrosion measurement:

ELECTRONIC SCANNING:
The ability to move a sound wave along the arrangement of elements without mechanical movement is called electronic scanning.

This scan is limited to the number of elements, the way elements are arranged and the number of channels in the processor system.

Using phased array linear scan to check internal corrosion

SECTORIAL SCANNING:
In this case, the wave bundles remain unchanged due to changes in the rules of the focal point and the delay time in a spread angle interval and the number of active elements.

Use of Phased Array sectorial scan in turbine blade investigation

Introduction of corrosion measurement methods:

Corrosion measurement is done according to the type of report and analysis required and is generally done in the following three ways

1- Fully automatic surface corrosion measurement (Corrosion Mapping):

The combination of Phased Array device and fully automatic scanners that are used in two X and Y axes.
By providing a scanning plan, it records the corrosion conditions of the surfaces in specific meshes (for example, 50×50 cm).
ELECTRONIC SCANNING technique is used in this method.
Fully automatic corrosion measurement reports are used to check corrosion area, remaining thickness, corrosion position in XYZ axes, and use for FFS, RBI inspections.
In the view from above, the stored ultrasound information that displays the part’s width axis and length axis.
The side view shows the stored ultrasound information from all linear scans side by side and the part length axis and the part depth axis.
There is no limit to the display of extensive corrosion
By drawing the horizontal and vertical axes from the observed defect, the coordinates of the defect are (400,120).

2-Corrosion measurement by Manual Encoded method:

In this method, Phased Array device and Wheel probe scanners are used.
By providing a scanning plan, record the corrosion conditions of surfaces with a width of about 5 cm and a free length.
ELECTRONIC SCANNING technique is also used in this method.
Top view of the stored ultrasound information showing the part width axis and length axis.
The side view shows the stored ultrasound information from all linear scans side by side and the part length axis and the part depth axis.

General view of a part with artificial defects

Merged C-Scan view using 3 separate scans:
In this output, any defect is shown regardless of the depth of corrosion, and it is suitable for detecting the general form of corrosion

Merged Depth Color view using 3 separate scans:
In this output, the depth of defects can be coded by colors. (For example: red: 75% corrosion, orange: 50% corrosion, green: 30% corrosion, blue 20% corrosion, white 10% corrosion, and yellow less than 2% corrosion)

And in the instructions, he put the colors as criteria for rejecting or accepting the results

How to show the top view of the thickness change in a glass block

How to show the top view of the thickness change in a glass block

3-Corrosion measurement by manual method:

In this method, the sensitive points are manually scanned and the image recording is done only from the corrosion points
The best setting in this method is the simultaneous use of Sectorial and Linear methods.
Corrosion measurement reports are stored in defective areas and can be presented in the following form to determine the depth of corrosion and determine the approximate form of corrosion.

Comparison of traditional and advanced ultrasonic corrosion measurement:

In general, corrosion measurement by TR probes and phased array method can be compared as follows:

In the phased array method, it is possible to record images of corrosion profiles.
If automatic and semi-automatic methods are used, the accuracy of measuring the extent of corrosion is higher
Due to the wide range of waves in the phased array method, the speed of testing increases without reducing accuracy