(1)Remove corroded material and blend out the damage.
NOTE: The base of the depth gage shall be flat against the undamaged surface
on each side of the corrosion. When taking measurements on concave or
convex surfaces, place the base perpendicular to the radius of curva-
ture of the surface as shown in Fig. 2.
(2)Position the depth gage as illustrated in Fig. 2 and determine the mea-surement reading.
(3)Take several additional depth readings.
(4)Select the deepest reading as the depth of the corrosion damage.
Volume 1
20-40-00
Page 4
OCT 01/01
F. Measuring Corrosion Damage with Impression Materials. In the event the cor-rosion area is inaccessible for use of the dial depth gage the use of
impression materials is recommended.
(1)Clay. Modeling clay or similar materials may be used for making impres-sions of the corrosion damage. Accurate measurements of the depth of
corrosion damage can be made by a comparator or other accurate measure-ment means.
(2)Silicone flexible mold compound rubber RTV 630A and RTV 630B from Gen-eral Electric Co. (V01139) may be used to make impressions of corrosion
damage and will be more permanent than the clay impressions. Measure-ments can be made by comparator or other accurate measurement means.
G. Rework Limits. The maximum rework limitations should be determined from the
criteria referenced in Volume 2. If no criteria are available and the damage
is on primary structure, consult The Boeing Company. To ensure that allow-able limits are not exceeded, an accurate measurement of the material
removed or material remaining in the reworked area after fairing should be
made. If the corrosion damage is in a previously worked area, the material
removed must include the thickness remove during previous rework.
4. Corrosion Rework Preparations:
A. Prior to starting any corrosion rework the airplane and the affected corro-sion area must be prepared as outlined in the procedures below. Personnel
performing these procedures shall observe all safety precautions for han-dling the materials used.
(1)Position airplane in wash rack or provide apparatus which will permit
rapid rinsing of all affected surfaces of the airplane.
(2)Statically ground the airplane (Ref Maintenance Manual Chapter 20).
WARNING: BATTERIES SHOULD BE DISCONNECTED WHEN WORKING IN THE VICINITY OF
BATTERY-OPERATED ELECTRICAL EQUIPMENT, ESPECIALLY WHEN FLAMMABLE
MATERIALS ARE BEING UTILIZED.
(3)Removed or disconnect airplane batteries as required.
NOTE: Some preventive maintenance procedures also require large quantities
of water to be used, such as paint removal and alodizing. In these
instances, disconnecting batteries is also prudent if there is elec-trical equipment in the area.
(4)Protect the pitot-static openings, louvers, airscoops, engine openings, 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：757 防腐手冊 CORROSION PREVENTION MANUAL 第二冊 一般信息(19)
