AC 43-206

Change 1

Advisory circular · Inspection, Prevention, Control, and Repair of Corrosion on Avionics Equipment

Approved
August 7, 2024
Last reviewed
August 12, 2024
This change
CHG 1 of AC 43-206.
Cancels
AC43-206
Family
AC 43-206 · 2 versions
Revision
change 1
14 CFR parts
43
Cited by
2 ADs

Guidance, not mandatory unless a rule or AD requires it. DRS record last changed November 21, 2025.

Show pages 212–223
Page 224 · 1Open in PDF

Index

COMPREHENSIVE INDEX

SUBJECT PAGE A Abrasive Tools ......................................................................................................... 51, 53, 74, 95, 96

Aircraft Cleaning Compound Method184

Air Drying62

Alternate Cleaning Methods183

Aluminum ............................................................................. 8, 18, 32, 33, 34, 75, 121, 151, 163, 173

Aluminum Electrolytic Capacitors138

Aluminum Surface Treatment75

Anode ................................................................................................................................... 5, 17, 148

Definition5

Antenna Connectors ............................................................................................................... 120, 121

Antenna Mounting Area Preparation Procedures111

Antenna Systems ...................................................................................................................... 24, 111

Application of Coatings80

Application of Primer80

Application of Topcoat83

Aqueous Ultrasonic Cleaner52

ATE Cabinets, Doors, and Panels125

Atom5

Avionics Cleaning Equipment50

Avionics Cleaning Materials47

Avionics Cleaning Procedures54

Cleaning and Drying Restrictions ........................................................................................ 55, 56

Cleaning and Removal of Bacteria and Fungi58

Cleaning and Removal of Dust, Dirt, Grease, and Oil58

Cleaning and Removal of Silicone Lubricant .................................................................... 58, 130 Cleaning and Removal of Solder Flux Residue ....................................................... 37, 48, 57, 98

Fingerprint Removal57

Hand Cleaning Methods56

Hazardous Chemical or Material Identification Label ................................................... 49, 50, 73

Avionics Cleaning Equipment50

Cleaning Procedures54

Corrosion Cleaning Facility45

Hazards of Cleaning54

Materials Used for Cleaning46

Post-cleaning Procedures61

Pre-cleaning Criteria55

Solvent Ultrasonic Cleaner .......................................................................................... 53, 63, 127 Special Considerations ......................................................................................................... 26, 61 Surface Preparation ...................................................................................................... 59, 78, 149

Water Base Solvent Spray Booth51

When To Clean54

Avionics Test Equipment124

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Index B

Basic ESD Precautions176

Battery Compartment ....................................................................................................... 21, 100, 126

Battery Compartments, Boxes, and Adjacent Areas100

Beryllium Copper163-168

Bilge Areas ........................................................................................................................... 21, 39, 99

Bimetallic Junctions148

Black Plague35

Bonding/Ground Connection Electrical Resistance Test124

Electronic Equipment Shock Mount158

Preservation ................................................................................. 45, 64, 123, 125, 139, 158, 184

Boric Acid Neutralizing Solution101

Bromothymol Blue Indicating Solution ................................................................................. 100, 103 Litmus Indicating Solution .............................................................................................. 100, 103

Preparation of Solution for Cleaning and Neutralizing Battery Electrolytes100

C Cadmium ................................................................................................ 8, 18, 32, 100, 121, 148, 149

Catastrophic Failures175

Cathode ......................................................................................................................................... 6, 15 Chemical Conversion Material Procedures .......................................................................................... 74, 75

Magnesium Surface Treatment76

Post-Treatment of Conversion Coated Surfaces77

Surface Treatment .................................................................................................................. 9, 74

Treatment of Other Metals77

Cleaning Neutralizing Procedure .................................................................................................... 102, 103 Priority ............................................................................................................................. 181, 182 Surface Preparation ........................................................................................ 59, 78, 96, 149, 171

Versus Calibration124

Coaxial Connectors ........................................................................................ 6, 53, 65, 119, 120, 145 Cockpit Cockpit and Control Boxes ...................................................................................... 105, 106, 136

Cockpit Area Components188

Compounds Electrolyte ................................................................................. 5, 6, 13, 15-17, 44, 100, 125, 169 Electron .............................................................................................................. 5, 6, 87, 169, 172

Electron Conductor6

Galvanic Couple .................................................................................................................... 6, 17 Ion .......................................................................................................................................... 6, 15

Condensed Moisture11

Copper ......................................................................... 7-10, 33-35, 148, 151-158, 163-166, 169, 171 Corrosion Aluminum Surface Treatment .............................................................................................. 32, 75

Effects of Solder Flux37

Effects on Metals32

Effects on Nonmetals36

Factors Influencing6

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Index

Fatigue19

Prevention Philosophy21

Preventive Maintenance and Control20

Prone Areas21-26

Electromechanical25

Electronics ........................................................................................... 25, 31, 83, 90, 91, 162 Moisture and Other Fluid Intrusion Sources ...................................................... 21, 24-26, 32 Special Considerations .................................................................................................. 26, 61 Structural ......................................................................................... 24, 74, 77, 108, 111, 146 Resistant Steel ............................................................................................................. 32, 151-156

Theory5

Anode .................................................................................................................. 5, 6, 15, 148 Atom .................................................................................................................................. 5, 6 Cathode ................................................................................................................ 6, 15, 18, 33 Visual Inspection . 28-31, 58, 60, 98, 111, 126, 133, 139, 141, 142, 144-146, 169-171, 187-189, 193, 194 Corrosive Conditions and Elements ................................................................................. 8, 10, 13, 44

Condensed Moisture11

Man-made Environments13

Micro-organism, Insect, and Animal Attack .................................................................. 13, 31, 38 Moisture ............................................................................................................................ 7-11, 13 Other Fluids ......................................................................................................................... 11, 21 Pressure ................................................................................................................................ 11, 13 Temperature ................................................................................................................. 8, 9, 11, 13 Crevice Corrosion ....................................................................................................................... 15, 16 D

Damaged Items194

Discharge Sensitive Equipment172

Desiccants70-72

Direct Failures175

Disassembly Inspection Procedures193

Dissipation of Static Charges176-178

ESD Protection Guidelines176-180

Drying and Preservation of Non-removable Avionics equipment ................................... 190, 191 Drying ..................................................................................................................................... 184, 185

Air Drying62

Coated Equipment88

Preparation62

Preservation Procedures184-186

Solvent Vapor Drying63

with Circulating Air Oven ............................................................................................. 62, 63 with Forced Air Oven ............................................................................................ 63, 98, 184 with Hot Air Blower .................................................................................................... 62, 185 with Vacuum Oven ................................................................................................ 63, 89, 185

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Index E Edge Connectors and Mating Plugs ............................................................................... 130, 137, 145 Effects of Corrosion ............................................................................................................ 24, 25-28, 31-44

Dust/Lint Accumulation44

Insect and Animal Attack38

Microbial Attack37

Electrical Bonding and Grounding Straps ........................................................................................ 109, 130

Bonding/Grounding Connections148-158

Bimetallic Junctions148

Hardware ................................................................................................... 148, 151, 153, 156

Connector and Wave guide Caps69

Connectors and Receptacles191

Equipment Shock Mount Bonding Preservation158

Motors and Generators188

Electrolyte ....................................................................................... 5, 6, 13-17, 19, 44, 100, 125, 126

Electron Conductor6

Electrostatic Voltages174

Emergency Cleaning Procedures ......................................................................................... 182-184, 192-195

Aircraft Cleaning Compound184

Alternate Methods ..................................................................................................... 183, 184

Primary Method183

Solvent Method183

Water-Displacing Method .................................................................................. 184, 186-191 Drying and Preservation .................................................................................................. 184, 185

Drying and Preservation Procedures185

Heated Compartment185

Hot Air Blower185

Vacuum Oven Drying185

Vented Drying Oven185

Vented Drying Oven (Bulb Type)185

Preparations181

Emergency Reclamation Team.................................................................................. 181, 192

Production Planning182

Required Tools, Materials, and Equipment182

Reclamation Team Organization181

EMI

Definition159

Precipitation Static162

Protection Maintenance168-171

Shielding Structures162-165

Shielding Design Goals162

Types of Protection162-168

Encapsulates83-98

Drying of Coated Equipment88

Fungus-Proof Coating86-89

Fungus-Proof Varnish86

Methods of Application88

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Index

Potting Compounds83-86

Sealant ....................................................................................................................... 84, 85, 90-92

Special Precautions89

Environmental Conditions .......................................................................................................... 10, 21

Environmental Factors10

Equipment Bays ..................................................................................................... 29, 30, 47, 99, 100 Equipment Hinges and Latches .............................................................................................. 108, 109 ESD

Corrosion Inspection and Repair180

Definition172

Direct Failures175

Packaging Practices ......................................................................................................... 177, 180

Protection Guidelines178

Susceptible Equipment175

Workstation Shop Practices ............................................................................................. 177, 180

Evaluation of Corrosion Damage31-44

Exfoliation Corrosion19

External Corrosion Removal and Cleaning ...................................................................... 77, 140, 141

External Mounted Equipment105

F

Factors Influencing Corrosion6

Moisture Intrusion ......................................................................................................... 6, 9-12, 21 Failure Mechanisms ............................................................................................................... 174, 175 ESD-Related Failure of Components ............................................................................... 174, 175 Filters .............................................................................................................................. 145, 162, 168

Fingerprint Removal57

Flush or Dome Antenna Mountings ....................................................................................... 119, 120

Frames, Mounting Racks, and Shock Mounts103

Fretting Corrosion16

Fungus-Proof

Coatings86

Varnish86

Fuselage Shielding162

G Galvanic Corrosion ........................................................................................................... 17, 121, 169 Galvanic Couple ........................................................................................................................... 6, 17

Generation of Static Charges172-174

General Inspection Procedures30

Gold and Gold Plating ........................................................................................... 8, 10, 16, 18, 33-35 H

Hand Cleaning Methods56

Handling ............................................................. 10, 13, 24, 45, 46, 68, 69, 73, 77, 78, 121, 132, 176 Hardware Selection ................................................................................................................ 148, 149

Hazardous Chemicals and Waste Generation49

Hazards of Cleaning54

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Index Heated Compartment .............................................................................................................. 185, 186 Hermetically Sealed Avionics Equipment .................................................................................. 9, 187 High Temperature ....................................................................................................................... 13, 92 Hot Air Blower ................................................................................................................. 62, 182, 185

How to Preserve66

Human Body Generated ESD174

Humidity Indicators72

I

In-Place Cleaning190

Inspection Procedures169

General Inspection Procedure30

Inspection Factors28

Water Intrusion Inspection30

Intermittent Failures174

Intergranular Corrosion .............................................................................................................. 19, 34 Internal Cleaning of

Automatic Test Equipment125

General Purpose Test Equipment125-128

Microwave Test Equipment129

Support Equipment ..................................................................................... 45, 107, 124-128, 182 Intrasystem/Intersystem EMI ................................................................................................. 160, 167 Ion ................................................................................................................................................. 5, 15 Iron and Steel ................................................................................................................................ 7, 32 J K L

Latent Failures175

Lighting Systems and Assemblies133

Lightning ................................................................................................................................ 161, 162

Litmus Indicating Solution100

Long Wire and Direction Finder (DF) Sense Antenna Corrosion123

Prevention Procedures123

Lubricants68

M

Maintenance Functions77

Magnesium ........................................................................ 7, 9, 18, 33, 74-76, 83, 108, 151, 153, 155

Magnesium Surface Treatment76

Man-made Environments13

Manufacturing Processes9

Material

Compatibility8

Selection and Use7

Identification Label49

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Index Used for Cleaning ........................................................................................................... 46-49, 53

Metallic Equipment Covers and Housings107

Methods of Application88

Methods of Minimizing the Effects of ESD177-180

Meters ............................................................................................................................... 89, 124, 126

Micro-organism, Insect, and Animal Attack13

Military Specifications6

Moisture and Other Fluid Intrusion Sources .......................................................................... 9, 11, 21 Traps and Cavity Areas ........................................................................................................ 7, 109

Mounting Racks and Shock Mounts189

Multi-pin Electrical Connectors, Cleaning and Preservation .......................................... 130, 139-145 N Nonmetallic Deterioration .......................................................................................................... 19, 36 Non-removable Avionics Equipment ..................................................................................... 190, 191 O Operator and Instrument Panels ............................................................................................. 126, 127

Operator/Unit Level Emergency Cleaning Procedures186-192

Antennas189

Cockpit Area Components ............................................................................................... 188, 189

Electrical Connectors and Receptacles191

Electric Motors and Generators188

Hermetically-Sealed Avionics Equipment187

In-Place Cleaning190

Mounting Racks and Shock Mounts189

Non-removable Avionics Equipment190

Removable Avionics Equipment186

Switches and Circuit Breakers188

Terminal Boards, Junction Boxes, Relay Boxes, and Circuit Breaker Panels191

Wiring Harnesses and Cables192

P Packaging

and Storage68-72

Desiccants70-72

Electrical Connector and Wave Guide Caps69

Handling ............................................................................................................................... 68, 69

Humidity Indicators72

Paint Systems ........................................................................................................................... 78, 131 Painting Equipment and Materials ............................................................................................. 78, 79 Pitting ............................................................................................................................. 16, 32, 34, 36

Post-Cleaning Procedure61

Post-Treatment of Conversion Coated Surfaces77

Potting Compounds ............................................................................................................. 83-86, 140

Precipitation Static162

Preservation

How to Preserve66

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Index Preservative Materials ................................................................................................................ 66, 67 What Not to Preserve ........................................................................................................... 65, 66

What to Preserve65

When to Preserve ................................................................................................................. 64, 65

Why Preserve64

Pressure Air .................................................................................................................................. 13, 51, 72

Contact12

Prime Sources of Static Charge172-174

Production Planning182

Program Requirements20

Proper Package Practices .......................................................................................................... 69, 180

Protective Coatings77-83

Application of Coatings80

Application of Primer80

Application of Topcoat83

Printed Circuit Boards (PCB) .................................... 7, 8, 16, 50, 51, 53, 62, 68, 84, 93-98, 130, 145

Purple Plague35

Q R

Radar Antenna Associated Hardware121

Radar Dish Antenna Corrosion Prevention Procedures121

Recognizing Avionics Corrosion31

Aluminum32

Black Plague35

Cadmium35

Corrosion Effects of Solder Flux37

Corrosion Effects on Nonmetals36

Corrosion Resistant Steel32

Copper33

Effects of Insect and Animal Attack38

Effects of Microbial Attack37

Gold and Gold Plating35

Iron and Steel32

Magnesium33

Nickel35

Purple Plague35

Red Plague35

Silver35

Tin35

Recommended Practices for ESD Sensitive Equipment180

Basic ESD Precautions178-180

Packaging Practices178-180

Sensitive Device Handling Practices178-180

Testing and/or Repair Practices178-180

Red Plague35

Relay and Circuit Breakers135

Removal and Cleaning of Identification and Modification Plates186

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Index Removal Priority .................................................................................................................... 181, 186 Repair of

Avionics Equipment Housings, Mounting Racks, and Storage Hardware99-111

Bilge Areas99

Cockpit and Control Boxes105

Electrical Bonding and Grounding Straps109

Engine Compartments100

Equipment Bays99

Equipment Covers, Hinges, and Latches ................................................................... 107, 108

External Mounted Equipment105

Frames, Mounting Racks, and Shock Mounts103

Internal Metal Surfaces146

Moisture Traps and Cavity Areas109

Terminal Boards, Junction Boxes, Relay Boxes, and Circuit Breaker Panels107

Avionics Systems, Equipment, and Components111

Aluminum Electrolytic Capacitors138

Antenna Bonding/Ground Connection124

Electrical Resistance Test124

Antenna Connectors121

Antenna Mounting Area Preparation Procedures .............................................. 111, 116, 119

Antenna Systems111

ATE Cabinets, Doors, and Panels125

Battery Compartments ............................................................................................... 100, 126

Cleaning Versus Calibration124

Coaxial Connectors145

Corrosion Visual Inspection .............................................................................. 111, 169, 170

Edge Connectors and Mating Plugs137

External Corrosion Removal and Cleaning ............................................................... 140, 141

Filters145

Flush or Dome Antenna Mounting119

Handling, Storage, and Packaging132

Internal Cleaning of General Purpose Test Equipment128

Internal Cleaning of Microwave Test Equipment129

Internal Corrosion Removal and Cleaning142

Lighting Systems and Assemblies133

Long Wire/Direction Finder Sense Antenna123

Meters126

Multi-pin Electrical Connectors, Cleaning, and Preservation ................................... 130, 139

Operator and Instrument Panels126

Painting Systems131

Printed Circuit Boards ............................................................................................... 130, 145

Battery Compartments, Boxes, and Adjacent Areas100

Radar Antenna Associated Hardware121

Relays and Circuit Breakers ............................................................................................. 130, 135 Sealing Connector Back shells ......................................................................................... 143, 144

Sensitive Internal Metal Surfaces146

Special Cleaning Procedures130

Support Equipment/General Purpose Test ....................................................................... 127, 128 Equipment Covers and Housings ..................................................................................... 107, 125 Switches ........................................................................................... 105, 126, 127, 130, 136, 188

Temporary Dish Protection121

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Index

UHF/VHF/ADF Antenna Sealing122

Wave guide Feed Horns133

Wave guides ....................................................................................... 24, 51, 56, 69, 87, 129, 132

Wet-Slug Tantalum Capacitors137

Wire Harnesses and Cables .............................................................................................. 145, 192 Repair Station

Cleaning Priority193

Damaged Items194

Disassembly Inspection Procedures193

Emergency Cleaning and Preservation Procedures194

Emergency Reclamation Team ........................................................................................ 181, 192

Initial Screening Procedure193

Required Tools, Material, and Equipment182

Undamaged Items194

S

Sealants90

Shelves, Bulkheads, and Crevices109

Shielding Requirements162-165

Silver .................................................................................................................................... 8, 35, 173

Sodium Bicarbonate Neutralizing Solution101

Solvent Ultrasonic Cleaner53

Solvent Method183

Solvent Vapor Drying63

Special Cleaning Procedures130

Special Considerations ............................................................................................................... 26, 61

Special Precautions89

Stress Corrosion19

Support Equipment .............................................................................................. 45-53, 125-129, 182

General Purpose Test Equipment125-128

Covers and Housings ....................................................................................................... 107, 125 Surface Preparation ....................................................................................................... 59, 78-82, 149 Surface Treatment ................................................................................................... 9, 74-77, 112, 171

Chemical Conversion Materials Procedures74-77

Switches and Circuit Breakers ................................................................................................ 136, 188 T Temperature ....................................... 8, 9, 11, 13, 26, 62, 63, 76, 77, 84, 85, 88-90, 92, 95, 184, 185

Temporary Dish Protection121

Terminal Boards, Junction Boxes, Relay Boxes, and Circuit Breaker Panels ....................... 107, 191 Testing and/or Repair Practices .............................................................................................. 178, 179 Tin .............................................................................................................................. 7, 10, 18, 34, 35

Treatment of Other Metals77

Triboelectric Series ................................................................................................................. 172, 173 Types of Corrosion ................................................................................................................ 15, 31-36

Crevice Corrosion15

Exfoliation Corrosion19

Fretting Corrosion16

Galvanic Corrosion ................................................................................................................ 8, 17

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Index Intergranular Corrosion ........................................................................................................ 19, 34

Metal Ion Concentration Cell15

Nonmetallic Deterioration19

Oxygen Concentration Cell15

Pitting16

Stress Corrosion19

Uniform Surface Corrosion15

Types of ESD Failures

Catastrophic Failures175

Intermittent Failures174

Typical ESD Protective Packaging Workstation177

U

UHF/VHF/ADF Antenna Sealing122

Undamaged Items194

Uniform Surface Corrosion15

V Vacuum Oven Drying ........................................................................................................ 63, 89, 185 Vented Drying Oven ................................................................................................................ 63, 185 Vented Drying Oven (Bulb-Type) ............................................................................................ 63, 185 Visual Inspection ............................ 8, 28-31, 58-60, 99, 111, 125, 133, 138-142, 169, 170, 193, 194 W Water Displacing and Treatment ........................................................................................ 144, 183, 194

Displacing Method184

Intrusion .................................................................... 6, 9-13, 21, 25, 30, 31, 55, 65, 90, 140, 145

Intrusion Inspection30

Base Solvent Spray Booth ................................................................................................... 51, 52

Wave guide Feed Horns133

Wet-Slug Tantalum Capacitors137

What Not to Preserve ................................................................................................................. 65, 66

What to Preserve65

When to Preserve ........................................................................................................................ 64, 65

Why Preserve64

Wire Harnesses and Cables .................................................................................................... 145, 192 X Y Z

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Advisory Circular Feedback Form If you find an error in this AC, have recommendations for improving it, or have suggestions for new items/subjects to be added, you may let us know by contacting the Flight Standards Directives Management Officer at 9-AWA-AFB-120-Directives@faa.gov.

Subject: AC 43-206, Inspection, Prevention, Control, and Repair of Corrosion on Avionics Equipment Date: _____________________ Please check all appropriate line items:

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