1、 FORD LABORATORY TEST METHOD BQ 003-05 Date Action Revisions 2000 08 10 Editorial no technical change A. Cockman 1992 08 03 Printed copies are uncontrolled Page 1 of 5 Copyright 20 00, Ford Global Technologies, Inc. DETERMINATION OF THICKNESS OF BLACK CHROMIUM PLATE Application This procedure is a r
2、apid, accurate method for determining the thickness of black chromium plate by measuring the time required to deplate a given area under specific conditions. The proced ure is applicable to black chromium plate over nickel, copper, chromium, stainless steel, etc. Apparatus Required The equipment nec
3、essary to conduct the test is described below. Assembly of the equipment is shown in the drawing and wiring diagram accom panying this procedure. Equipment is similar to FLTM BQ 003 - 01, however, the constants used in this method give better accuracy. Electrolytic Cell The cell which contains the e
4、lectrolyte consists of a stainless steel tube 38 mm in length with a 6.3 mm in side diameter. The cell is fitted on one end with a rubber grommet having an accurately dimensioned 3.2 mm diameter hole. The grommet makes contact with the test specimen and restricts the electrolyte to a definite test a
5、rea of 3.2 mm. The outer surface of the cell, if held in a fixture, should be insulated from other conductors. Milliammeter A milliammeter with a 0 - 10 milliampere range is connected to the circuit and indicates the flow of current through the cell. Resistors A fixed resistor of 30,00 0 ohms and a
6、variable resistor of 100,000 ohms regulates the flow of current. Voltmeter A vacuum tube voltmeter with a low side of 0 - 5 volts is connected across the cell to indicate the removal of the plate from the test area of the sample. When the te st is started, the indicator of the voltmeter rises to a p
7、oint on the scale and then remains fixed until the plate is removed and then changes, indicating completion of the deplating process. Power Source Two 45 V dry “B“ batteries are connected in series to provide a 90 V power source. Timer A stopwatch or other timing device is required which will record
8、 the duration of the test in seconds. FORD LABORATORY TEST METHOD BQ 003-05 Page 2 of 5 Copyright 2000, Ford Global Technologies, In c. Calibration of Equipment The apparatus shall be calibrated by means of standard samples having a known chromium plate thickness. Solutions Required Sodium Hydroxide
9、 - 10 % Dissolve 120 g of NaOH in 1000 mL of distilled water, cool and dilute to a sp. gr. of 1.1089. Conditioning and Test Conditions All test values indicated herein are based on material conditi oned in a controlled atmosphere of 23 +/ - 2 C and 50 +/ - 5 % relative humidity for not less than 24
10、h prior to testing and tested under the same conditions unless otherwise specified. Procedure 1. Clamp the positive lead to the test specimen and place the electrolytic cell firmly on the area to be checked and fix in this position with a clamp or other suitable holding fixture. Note: Any grease, or
11、ganic coatings, etc. which might interfere in the test should be removed from the test specimen with a su itable cleaning agent. 2. Fill the electrolytic cell with the sodium hydroxide solution. Medicine dropper or buret is convenient for this purpose. 3. Simultaneously close the switch and start th
12、e timing device. Adjust the current flow to 4 milliamperes with the variable resistor. Once set, subsequent determinations may be made without further adjustment. 4. When the vacuum tube voltmeter shows a deflection, stop the timing device and shut off the current. 5. Read the black chromium plate t
13、hickness fr om a time - thickness chart similar to the one attached. This chart should be prepared from standards having a known chromium plate thickness. Notes on the Procedure 1. At the start of the test and until the base metal is exposed, a voltage characteristi c of the black chromium plate exi
14、sts across the cell. When all of the plate has been removed from the test area, the voltage rises sharply and assumes a new value which is characteristic of the base metal. FORD LABORATORY TEST METHOD BQ 003-05 Page 3 of 5 Copyright 2000, Ford Global Technologies, In c. 2. If the current is maintain
15、ed constant, the t ime for deplating will be proportional to the thickness of the plate. 3. The electrolyte does not attack the plate unless current is flowing through the cell. 4. A recorder may be attached to the equipment to indicate the plate thickness A Leeds and Nor thrup Speedomax Type G, 0 -
16、 5 millivolts, paper speed 2 inches/minute, is recommended. If a recorder is used it should draw less than 100 microamps at 1.5 volts. The cell voltage output (approximately 1.5 - 20 volts) should be matched to the recorder. Chemicals, materials, parts, and equipment referenced in this document must
17、 be used and handled properly. Each party is responsible for determining proper use and handling in its facilities . FORD LABORATORY TEST METHOD BQ 003-05 Page 4 of 5 Copyright 2000, Ford Global Technologies, In c. DETERMINATION OF THICKNESS OF BLACK CHROMIUM PLATE Time Thic kness Chart Black Chromium Plate FORD LABORATORY TEST METHOD BQ 003-05 Page 5 of 5 Copyright 2000, Ford Global Technologies, In c. DETERMINATION OF THICKNESS OF BLACK CHROMIUM PLATE Test Equipment Chromium Plate Thickness Test
