1、 FORD LABORATORY TEST METHOD BI 169-01 Date Action Revisions Rev 00 2011 07 14 Activated J. LaDuke, NA Controlled document at www.MATS Copyright 2011, Ford Global Technologies, LLC Page 1 of 4 MEASUREMENT OF CORROSION PROPAGATION FROM A SCRIBED LINE Application This method covers the scribing of coa
2、tings on metal surfaces to expose the base metal using a handheld tool. After corrosion testing, the method for measuring the amount of corrosion propagation from the scribed line is explained. Apparatus Required Scribing Tool A scribe tool with carbide cutting edge or hardened steel edge will be us
3、ed. The cutting edge will ensure a constant width over the length of the scribe. The cutting tool shall be capable of producing a single cut over multiple passes of the tool. There are several possible designs. One design is shown in Figure 1. This scribe tool tip is provided by Valenite having part
4、 number VBGT 331 PF3 VP9610 turning tip. An example of a hand-held scribe is shown in Figure 2. Figure 1 Cutting Tip Example FORD LABORATORY TEST METHOD BI 169-01 Controlled document at www.MATS Copyright 2011, Ford Global Technologies, LLC Page 2 of 4 Maintenance: Tool shall be inspected for wear a
5、nd breakage before each test. Damaged or worn scribes shall be replaced. Measuring Device A scale measuring device capable of reading with an accuracy of 0.5 mm. Scribing Procedure 1. The scribing tool shall be applied so the cutting edge is approximately 800 angle in the scribe line direction and 9
6、00 angles with the plane of the panel. See Figure 3 and Figure 4 respectively. Figure 3 Figure 4 Figure 2: Hand Held Scribe Example 800 angle 900 angle Direction of Scribe Direction of Scribe Cutting Tip FORD LABORATORY TEST METHOD BI 169-01 Controlled document at www.MATS Copyright 2011, Ford Globa
7、l Technologies, LLC Page 3 of 4 Scribing Procedure: Continued 2. Scribed line between 70 mm to 100 mm in length. The scribe should be straight and free of metal burrs. Note: The scribe must extend down to the metal substrate. Multiple passes over the same line may be required. For some coatings it h
8、elps to apply minimal pressure on the first scribe to avoid fracture and chatter of the paint system surrounding the line. For zinc coatings on steels a minimum of three passes is recommended. 3. The scribing angle requirement shall be maintained on curved surfaces to the best of ones ability. 4. Fl
9、at test panels may have a diagonal line along with a horizontal line. When requested, these lines should have requirements outlined on Figure 5. 5. For component testing a horizontal scribed line is required. 6. Unless otherwise indicated, by the corrosion test procedure, the flat panel is intended
10、to be oriented 150 +/- 50 from the vertical with the scribe lines facing upward. Figure 5 Flat Panel 300 +/- 150 angle 00 +/- 50 angle 20 mm min 10 mm min FORD LABORATORY TEST METHOD BI 169-01 Controlled document at www.MATS Copyright 2011, Ford Global Technologies, LLC Page 4 of 4 Evaluation Proced
11、ure 1. After the completion of the corrosion test, review the scribed line and observe the corrosion spread away from the scribed line. 2. Disregard the first and last 10 mm of the scribed line. 3. Divide the line into five equal segments. (each segment being 6 mm minimum in length) See Figure 6. 4.
12、 Measure the maximum propagation of corrosion with a reading of accuracy of 0.5 mm for each segment. 5. Use the formula in the calculation section to determine the mean value. 6. The report shall contain an account of the mutually agreed upon number of specimens. Typically the largest mean value of any one specimen (Horizontal or Vertical scribes) is applied against a requirement value. Figure 6 Scribed Line after Corrosion Calculations: Where: h = Width of scribed line X = Total maximum spread of corrosion above and below the line X1 X2 X3 X4 X5 h 10 mm 10 mm
