Figure 2-5 - Electrical Bonding Preparation - Terminal Lug - Garmin GFC 500 Maintenance Manual

Figure 2-5 – Electrical Bonding Preparation – Terminal Lug
2.4.2 Preparation of Aluminum Surfaces
The following general procedure is recommended to prepare an aluminum surface for proper
electrical bonding.
1. Clean grounding location with solvent.
2. Remove non-conductive films or coatings from the grounding location.
3. Apply a chemical conversion coat such as Alodine 1200 to the bare metal.
4. Once the chemical conversion coat is dry, clean the area.
5. Install bonding equipment at grounding location.
6. After bond is complete, if any films or coatings were removed from the surface, reapply a
suitable film or coating to the surrounding area within 24 hours.
After satisfactory electrical bond is achieved, when it has been necessary to remove any high-
resistance protective coating, the area from which the coating has been removed should be
refinished with the same finish as is on the rest of the part within 24 hours. In cases where the
parts come in with certain areas spot-faced, or if there is no finish on the part (bare metal), apply
conformal coating over the bond joint and hardware per MIL-I-46058 or clear lacquer per TT-L-
20A in order to facilitate future inspection. Refer to the model specific Aircraft Maintenance
Manual or Standard Practices Manual for surface protection requirements applicable to affected
areas. The correct material finish is important when mating untreated or bare dissimilar metals.
They should be galvanically compatible. When corrosion protection is removed to make an
electrical bond, any exposed area after the bond is completed should be protected again.
Additional guidance can be found in SAE ARP 1870 Section 5.
For a more detailed procedure, refer to SAE ARP 1870 Sections 5.1 and 5.5.
GFC 500 Autopilot with ESP Part 23 AML STC Maintenance Manual
190-02291-01
Page 9
Revision 1