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48IS LOGISTICS

You are about to take the Corrosion Control Training slide show. There is a test at the end of this presentation. Click PAGE DOWN. 48IS LOGISTICS. CORROSION CONTROL TRAINING. OVERVIEW. THE FOLLOWING SUBJECTS WILL BE COVERED DURING THIS TRAINING SESSION.

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48IS LOGISTICS

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  1. You are about to take the Corrosion Control Training slide show. There is a test at the end of this presentation. Click PAGE DOWN

  2. 48IS LOGISTICS CORROSION CONTROL TRAINING

  3. OVERVIEW THE FOLLOWING SUBJECTS WILL BE COVERED DURING THIS TRAINING SESSION 1. Theory and Causes of Corrosion 2. Corrosion Prevention 3. Corrosion Identification 4. Corrosion Removal 5. Corrosion Treatment 6. Local Corrosion Threats

  4. THEORY AND CAUSES OF CORROSION • Concept and Objective of CPCP • Corrosion Control Technical Publications • Electrochemical Theory of Corrosion • Biochemical Theory of Corrosion • Environmental Factors and Corrosion

  5. OBJECTIVE OF THE CPCP The purpose of the Corrosion Prevention and Control Program (CPCP) is to prolong the life of all USAF systems and equipment through corrosion prevention and proper treatment. Success of the CPCP depends upon you and every maintenance technician becoming properly trained and practicing proper corrosion prevention and treatment techniques.

  6. CORROSION CONTROL Technical Publications • TO 00-25-234 GENERAL SHOP PRACTICE REQUIREMENTS - A wealth of information on electric and electronic workmanship standards, soldering, printed circuit board repair, cable and connector fabrication, and many other related subject areas. It addresses cleaning procedures, corrosion prevention treatments, and protective coatings to be used during maintenance and repair actions.

  7. TO 1-1-8 APPLICATION OF ORGANIC COATINGS, AEROSPACE EQUIPMENT - In-depth guidance for application of protective coatings on all types of Air Force equipment. Selection of the proper coatings, and knowing exactly how to apply them is critical in corrosion prevention. • TO 1-1-689 AVIONICS CLEANING AND CORROSION PREVENTION-CONTROL - Although written for Air Force and Navy avionics systems, this TO provides valuable information on corrosion theory, preventive maintenance, corrosion treatment and repair, corrosion control procedures for electrical bonding and grounding, and equipment cleaning procedures.

  8. TO 1-1-691 AIRCRAFT WEAPONS SYSTEMS CLEANING AND CORROSION CONTROL - A joint Air Force, Army, and Navy aircraft oriented publication that contains in-depth corrosion theory, prevention, and treatment information. It also contains many informative charts and tables. • TO 31Z-10-37 CORROSION PREVENTION AND PROTECTION (TELECOMMUNICATIONS ENGINEERING) - Written specifically for ground C-E facilities. This TO covers corrosion theory, prevention, and treatment information and guidance in the ground communications environment during installation, operation, and maintenance.

  9. TO 00-25-234 All of these technical orders are available for reference in Maintenance Support, except for TO 1-1-691. This tech order can be found on P:\common\Tech Orders\. You can also find TO 00-25-234 and TO 1-1-8 on the P: drive.

  10. ELECTROCHEMICAL THEORY OF CORROSION Corrosion is the deterioration of a material caused by a reaction with the environment. The reaction is usually electrochemical but it can also be caused by biochemical factors. In each case, corrosion usually begins on the material surface and, if allowed to progress, works its way into the material core as shown below.

  11. Some types of corrosion originate within the material core, but most corrosion starts on the surface where it can be prevented or properly treated in its early stages. ELECTROCHEMICAL CELLS - The electrochemical process is similar to the current flow in a common dry cell battery. Corrosion by-products are formed when one part of a metal acts as a negative element (cathode) and another part acts as a positive element (anode). When an electrolyte is present, an electrochemical cell is formed and current flows between the two charged elements. The electrolyte may be an acid, alkali, or just plain moisture. The current flow destroys some of the anode material and forms by-products that appear as corrosion.

  12. ELEMENTS OF AN ELECTROCHEMICAL CELL To form an electrochemical cell, four elements are required: 1. Anode 2. Cathode 3. Electrolyte 4. Metallic contact between the anode and cathode The following figure depicts the electrochemical process.

  13. In the following figure, one of the four elements, the electrolyte, has been removed by using a protective coating. The basis of your corrosion control program is ensuring the integrity of all protective barriers and removing all electrolytes. This is due to the fact that the electrolyte is the only element you can easily control.

  14. BIOCHEMICAL THEORY OF CORROSION Although not as common, you need to be aware of biochemical corrosion. Biochemical corrosion is caused by fungi and waste products from animals and insects. FUNGI - Mold, mildew, smut and bacteria draw oxygen from the air and hold moisture against the material to which they are attached. An acid-based waste product is produced causing surface corrosion. Moisture contained in the fungi can also cause intermittent equipment problems that are very hard to isolate.

  15. ANIMALS AND INSECTS - Waste products normally include salts and acids which corrode metallic surfaces. They may also eat insulation, paint, or other protective coatings which exposes the surface to electrochemical corrosive attacks.

  16. ENVIRONMENTAL FACTORS AND CORROSION Moisture is the single most important environmental factor causing corrosion. Moisture present in the air often contains contaminants such as chlorides, sulfates, nitrates and other chemicals which accelerate corrosion. Sealed compartments can expand and contract with temperature variations, allowing moisture to enter. Temperature variations also cause condensation on equipment. Accumulations of dirt and debris can hold moisture against equipment, accelerating the corrosion process.

  17. California does not hold many records for rainfall, but it is still a consideration. The bottom line is: Keeping equipment clean and properly painted will greatly decrease the threat of corrosion by moisture.

  18. CORROSION PREVENTION • Air Force Corrosion Prevention Policy • Air Force Corrosion Prevention Philosophy • General Work Practices • Cleaning Equipment • Storage, Protection, And Handling Of Equipment

  19. AIR FORCE CORROSION PREVENTION POLICY AF Instruction 32-1054 establishes Air Force policy on corrosion prevention and control. It requires effective corrosion prevention programs for all maintenance activities to enhance safety, extend service life, reduce maintenance costs and repair man-hours, and minimize equipment downtime. All maintenance technicians must have an awareness of the causes of corrosion and practice corrective preventive techniques.

  20. AIR FORCE CORROSION PREVENTION PHILOSOPHY Important elements of corrosion prevention include: • INSPECT for corrosion on a SCHEDULED basis • TRAIN technicians in corrosion PREVENTION and RECOGNITION • Thoroughly CLEAN, PRESERVE, and LUBRICATE equipment at prescribed intervals • Use APPROVED MATERIALS, EQUIPMENT, and TECHNICAL PUBLICATIONS • Keep accurate RECORDS and report MATERIEL and DESIGN DEFICIENCIES that promote corrosion **Refer to TO 1-1-689, Chapter 3 for more detailed information**

  21. Reporting corrosion problems: Let’s dwell here for a moment. Reporting corrosion is one of the most overlooked steps of the entire process. Every time you find and treat corrosion, you should enter the correct information in CAMS. HOW-MAL CODES: 170 - Corroded (or) 667 - Corroded, Severe ACTION TAKEN CODE: “Z” - Corrosion Repair (ALWAYS) Do not forget to enter this in the Automated History when closing the write-up.

  22. If you suspect corrosion is somehow related to the manufacturing process, it is important that you submit a deficiency report through the USAF Deficiency Reporting System IAW TO 00-35D-54. Maintenance Support will assist you in this process. All corrosion problems with real property (buildings, and large antenna structures, manholes) need to be referred to the Unit Corrosion Control Monitor for coordination with the Base Civil Engineering Office. Corrosion on all vehicles should be documented on the form 1800s for each vehicle and brought to the attention of the Unit Vehicle Control Officer.

  23. GENERAL WORK PRACTICES AFQTP 2EXXX-201C (Corrosion Prevention and Control), TO 00-25-234 and the 31-10 series of TOs (Engineering-Installation Standards) covers general practices and corrosion prevention techniques. Always consult the appropriate Technical Orders prior to using a particular type of material or mechanical procedure • DO NOT mark on any metal surface with a graphite pencil or sharp object • DO NOT use graphite as a lubricant (it acts as a cathode to all structural metals) • DO NOT polish metal surfaces purely for cosmetic purposes (yes, it promotes corrosion)

  24. Place protective covers over equipment when drilling, grinding or sanding • Replace rusted screws, bolts and washers • Reapply worn or damaged protective coatings (yes, paint is a protective coating) • Keep equipment and work areas free of chips, grit, dirt, dust and foreign materials • Clean spills of any type thoroughly and as soon as they occur • Handle components and circuit boards carefully (salt and oil from on your fingers are highly corrosive) • Remove flux residue after soldering (when flux is combined with an electrolyte - you guessed it - it is corrosive)

  25. Perform detailed corrosion inspections in conjunction with equipment PMIs (all PMI workcards should require this). Check for the following: • Signs of corrosion by-products and equipment damage • Potential water traps • Presence of bacteria and fungi • Areas of dissimilar metal contact that may create corrosion • Presence of dirt, lint, and other contaminates • Adequacy of protective coatings • Failure of filter systems • Signs of moisture or fluids and evidence of faulty seals and gaskets that could allow moisture intrusion

  26. Train personnel in the recognition of corrosion inducing conditions, detection, preservation, treatment and lubrication • Report severe corrosion problems through command channels to the appropriate item manager Even under ideal circumstances, corrosion can’t be completely eliminated. Using the above practices will keep corrosion to a minimum.

  27. CLEANING EQUIPMENT An adequate cleaning program is essential to preventing corrosion. Equipment should be cleaned frequently using approved materials and prescribed procedures. Detailed information on correct cleaning procedure and various types of cleaning agents can be found in Chapter 4 of TO 1-1-689 and Chapter 3 of TO 1-1-691. Don’t overlook the specific equipment technical data when doing your research. NOTE Do not use commercial cleaners unless authorized by the appropriate TO.

  28. GENERAL PURPOSE CLEANER Good maintenance practices dictate using the mildest cleaning method to remove all contaminants. Reference the applicable technical order for the correct cleaning solution. There are numerous types of cleaners available. For most purposes, detergent and water are sufficient to remove dust, dirt and other soils.

  29. Cleaning Procedures: • Disconnect power and remove covers • Ensure all drain holes are open • Lubricated parts and natural entrapment areas need protection against damage from cleaning agents. Mask and protect these surfaces, areas, accessories and components • Use only authorized cleaning compounds • Apply the cleaning solution - never spray into electronic components • When complete, examine the area to ensure all contaminants have been removed • Check for signs of corrosion

  30. STORAGE, PROTECTION AND HANDLING OF EQUIPMENT Okay, now you know all about taking care of equipment. Something is missing from the picture. Your responsibility does not stop with mission equipment. Bench stock items, supply point materials, repair cycle assets, tools, TMDE, items awaiting parts and equipment in storage all must be protected and checked for signs of corrosion.

  31. All unused or inactive equipment must be protected from moisture by the use of dust caps and proper packaging techniques. Even the slightest amount of moisture can cause corrosion so equipment should be stored in a dry location. Spare parts and equipment should be stored in hermetically sealed containers or bags whenever possible. If this is not possible, use plastic sheeting and carefully seal the equipment with desiccant. Desiccant is a drying agent, but the chemicals used in desiccant are corrosive in nature, so ensure the desiccant bag is free from rips. It is also a good idea to tape the desiccant to the container to avoid contact with the equipment.

  32. Use of humidity indicators is also a good idea. If the area used for storage is in question, a humidity indicator will let you know if the are is suitable for storage. Handling of equipment: Most items come in some type of reusable container. Whenever storing or transporting equipment or TMDE, use the appropriate container. If one is not available, use sufficient padding to prevent scratches, dents and paint chips (ideal places for corrosion to start). Electrostatic Discharge Sensitive (ESDS) Components: All ESDS items will be handled, packaged and transported IAW TO 00-25-234.

  33. CORROSIONIDENTIFICATION • Uniform Surface Corrosion • Pitting Corrosion • Galvanic Corrosion • Filiform Corrosion • Concentration Cell Corrosion • Intergranular Corrosion • Exfoliation • Stress & Fatigue Corrosion • Visual Appearance Of Corrosion By-products On Common Metals

  34. UNIFORM SURFACE CORROSION This is the most common type of corrosion. Uniform corrosion takes place when oxygen, water, ozone, salt or other materials attack a metal surface. It is a localized chemical attack which occurs consistently and uniformly over the entire metal surface. It causes dulling of the surface initially and may progress until the surface has a rough texture or frosted appearance. Rusted iron, tarnished silver and frosted nickel are examples.

  35. PITTING CORROSION This is a common and more severe form of localized corrosion. Pitting corrosion occurs between grains of an alloy. It produces various shades of gray or white powder that form in blotches on the surface of the metal. When the deposits are removed, tiny pits or holes can be seen. Aluminum, magnesium and their alloys are very susceptible to this type of corrosion.

  36. GALVANIC CORROSION This type of corrosion occurs when two types of dissimilar metal are joined together. The mating of different types of metals and alloys promotes electrochemical cell formation and rapid material deterioration. Whenever you notice surface dulling, tarnish, powdery deposits or rust near joints, cowlings, rivets and mated surfaces, you should suspect galvanic corrosion. Note in the figure below, corrosion takes place on the anodic material.

  37. GROUP METALS I MAGNESIUM/MAGNESIUM ALLOYS; ALUMINUM/ALUMINUM ALLOYS; TIN II ALUMINUM; ZINC; CADMIUM; TIN; TIN-LEAD III ZINC; CADMIUM; STEEL; LEAD; TIN; NICKEL/NICKEL ALLOYS; TIN-LEAD; TITANIUM COPPER/COPPER ALLOYS; NICKEL/NICKEL ALLOYS; CHROMIUM; STAINLESS STEEL; GOLD; SILVER; TITANIUM IV COMPATIBLE GROUPING OF METALS To avoid galvanic corrosion, you must consider the properties of the metals you are using. Metals in Group I corrode the fastest. Metals in group IV are the most resistant to corrosion. If you must mix metals, try to use metals from the same group. If this is not possible, select the metal with the smallest area from the lower activity group (III & IV). Example: If aluminum fasteners from group II are not available to install on aluminum sheet, use fasteners from Group III or IV. If the TO allows, use sealants or primers to isolate the metals.

  38. FILIFORM CORROSION Not as common as the previous types of corrosion, this type is fairly easy to recognize and treat in its early stages. Filiform corrosion occurs on metal surfaces with organic coatings, such as petroleum oils and greases. It normally occurs when the relative humidity is between 78 and 90% and the surface is slightly acidic. It starts at breaks in the coating (scratches or nicks). Filiform corrosion has the appearance of worm like traces underneath the protective coating.

  39. CONCENTRATION CELL CORROSION Concentration cell corrosion usually forms in cracks and crevices, metal-to-metal joints, behind or under gaskets, sealants, electrical tape or other foreign material affixed to metallic surfaces. The cause of this type corrosion is an imbalance of oxygen and ions in electrolytes that tend to concentrate under the surface of the joint or foreign material. If not detected and corrected early, pitting corrosion usually results.

  40. The following types of corrosion are hard to detect until significant damage has occurred. When discovered, it is usually beyond your capability to repair.

  41. INTERGRANULAR CORROSION This type of corrosion occurs inside the grain of metals when dissimilar alloys exist side-by-side in the same metal. One alloy acts as the cathode and the other allot acts as the anode. Many times intergranular corrosion is the result of improper heat treatment during manufacture. Because intergranular corrosion begins internally, it is very difficult to prevent and detect.

  42. EXFOLIATION Exfoliation corrosion is the physical evidence of advanced intergranular corrosion. The metal surface is forced up by the expanding corrosion products below the surface. It can be identified by metal surface flaking, bumps and blisters, and metal peeling in layers near edges and joints. When exfoliation is detected, the only recourse is to replace the material.

  43. STRESS CORROSION Stress corrosion occurs when opposing or alternating pressure is applied to a metal surface or structure. This pressure produces cracks in the grains of the metal allowing moisture to penetrate. Electrochemical action sets in, minute cracks appear, split open, and lengthen until they become visible to the eye. Transportable shelters, antenna support structures and other types of equipment exposed to alternating pressure may experience stress corrosion. Look for minute cracks, incorrectly sized hardware, and indications of corrosion near joints, corners, and support bases.

  44. FATIGUE CORROSION Fatigue is the end result of other types of corrosion. When metal is subjected to repeated mechanical stress and chemical attack, it becomes fatigued and separates. Severe pitting, cracking, and separation along stress lines are evidence of fatigue corrosion.

  45. VISUAL APPEARANCE OF CORROSION BY-PRODUCTS ON COMMON METALS Recognizing corrosion is the key to an effective Corrosion Prevention and Control Program. The table on the next slide shows different metal susceptibilities and what corrosion by-products will look like.

  46. ALLOY TYPE OF ATTACK APPEARANCE Aluminum Alloy Surface, pitting and intergranular. White or gray powder Titanium Alloy Highly corrosion resistant. Extended or repeated contact with chlorinated solvents may result in embrittlement. Cadmium plated tools can cause embrittlement of titanium. No visible corrosion products Magnesium Alloy Highly susceptible to pitting. White powder snow-like mounds and white spots on surface Carbon and Low Alloy Steel (100-800 series) Surface oxidation and pitting, surface and intergranular. Reddish-brown oxide (rust) Stainless Steel (300-400 series) Intergranular corrosion. Some tendency to pitting in marine environment (300 series more resistant than 400 series). Corrosion evidences by rough surface; sometimes by red, brown or black stain Nickel-Base Alloy Generally has good corrosion resistant qualities. Sometimes susceptible to pitting. Green powdery deposit Copper-Base Alloy Surface and intergranular corrosion. Blue or blue-green powdery deposit Cadmium (used as a protective plating) Good corrosion resistance. Will cause embrittlement if not properly applied. White to brown or black mottling on the surface Chromium (used as a wear-resistant plating) Subject to pitting in the presence of sulfur. Is cathodic to steel, does not corrode, promotes rusting of steel where pits occur Silver Will tarnish in the presence of sulfur. Brown to black film Gold Highly corrosive resistant. Deposits cause darkening of reflective surfaces Tin Subject to whisker growth. Whisker-like deposits

  47. CORROSION REMOVAL • Safety • Corrosion Removal Tools And Materials • Corrosion Removal Procedures

  48. SAFETY Safety is the first consideration when performing corrosion removal. Common sense and use of proper protective equipment is a key player here. We will cover four hazards that require special attention. 1. HIGH VOLTAGE 2. RADIATION 3. FUMES 4. CHEMICALS

  49. HIGH VOLTAGE If there is even a remote chance of coming into contact with high voltages when removing corrosion, postpone the job until another time. Never endanger yourself! A second consideration is doing damage to the equipment. Take necessary precautions to protect the equipment from corrosion residue, metal chips and shavings. Always have a safety observer and post “DANGER - DO NOT ENERGIZE” signs on all applicable circuit breakers. Schedule the down time you need to perform the job correctly.

  50. RADIATION The same basic precautions taken around high voltage also applies to radiation hazards. Most radiation hazards are encountered by radar and antenna personnel. Corrosion control actions (or any maintenance) should not be performed on hot antennas. Again, schedule the down time that you need. Always post a safety observer and “DANGER - DO NOT ENERGIZE” signs where necessary.

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