Docstoc

Corrosion - PowerPoint

Document Sample
Corrosion - PowerPoint Powered By Docstoc
					    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

1.   Theory and Causes of Corrosion
2.   Corrosion Prevention
3.   Corrosion Identification
4.   Corrosion Removal
5.   Corrosion Treatment
6.   Local Corrosion Threats
       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
    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.
        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.
• 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.
• 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.
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.
       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.
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.
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.
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.
 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.
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.
   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.
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.
      CORROSION PREVENTION

• Air Force Corrosion Prevention Policy
• Air Force Corrosion Prevention Philosophy
• General Work Practices
• Cleaning Equipment
• Storage, Protection, And Handling Of Equipment
           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.
              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**
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.
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.
     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)
• 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)
• 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
• 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.
             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.
          Good maintenance practices
            dictate using the mildest
            cleaning method to remove
            all contaminants.
            Reference the applicable
            technical order for the
            correct cleaning solution.
GENERAL
PURPOSE
CLEANER
          There are numerous types of
            cleaners available. For
            most purposes, detergent
            and water are sufficient to
            remove dust, dirt and other
            soils.
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
      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.
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.
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.
               CORROSION
             IDENTIFICATION
•   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
       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.
              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.
             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.
                COMPATIBLE GROUPING OF METALS

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;
 IV      GOLD; SILVER; TITANIUM


  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.
               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.
       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.
The following types of
 corrosion are hard
 to detect until
 significant damage
 has occurred. When
 discovered, it is
 usually beyond your
 capability to repair.
          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.
                    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.
                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.
              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.
 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.
       ALLOY                                 TYPE OF ATTACK                                   APPEARANCE
Aluminum Alloy            Surface, pitting and intergranular.                          White or gray powder

Titanium Alloy            Highly corrosion resistant. Extended or repeated contact     No visible corrosion products
                          with chlorinated solvents may result in embrittlement.
                          Cadmium plated tools can cause embrittlement of titanium.
Magnesium Alloy           Highly susceptible to pitting.                               White powder snow-like mounds
                                                                                       and white spots on surface
Carbon and Low Alloy Surface oxidation and pitting, surface and intergranular.         Reddish-brown oxide (rust)
Steel (100-800 series)
Stainless Steel (300-400 Intergranular corrosion. Some tendency to pitting in          Corrosion evidences by rough
series)                  marine environment (300 series more resistant than 400        surface; sometimes by red,
                         series).                                                      brown or black stain
Nickel-Base Alloy        Generally has good corrosion resistant qualities. Sometimes   Green powdery deposit
                         susceptible to pitting.
Copper-Base Alloy        Surface and intergranular corrosion.                          Blue or blue-green powdery
                                                                                       deposit
Cadmium (used as a        Good corrosion resistance. Will cause embrittlement if not   White to brown or black
protective plating)       properly applied.                                            mottling on the surface
Chromium (used as a       Subject to pitting in the presence of sulfur.                Is cathodic to steel, does not
wear-resistant plating)                                                                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
       CORROSION REMOVAL


• Safety
• Corrosion Removal Tools And Materials
• Corrosion Removal Procedures
                    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
                  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.
                      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.
                        FUMES

Numerous electronic facilities use battery banks for back-up
  power or starting devices. Liquid cell batteries emit toxic
  and combustible fumes. The electrolyte used in batteries is
  highly corrosive, creating the need for continuous
  corrosion control measures. Exercise extreme caution to
  avoid inhaling fumes or creating sparks that could cause an
  explosion. Always wear goggles, rubber gloves and a
  rubber apron when performing corrosion control on
  batteries. Ensure eye wash is available. Avoid skin
  contact with the electrolyte. Never use power tools around
  batteries. Always use a safety observer.
                      CHEMICALS

Many corrosion preventives, cleaners, paint strippers, sealers
  and solvents are hazardous to the skin, eyes and respiratory
  tract. Observe all cautions and warnings listed on the
  manufacturers labels and Material Safety Data Sheets
  (MSDSs).
One final word on safety, keep your work area clean
 and free from clutter. This will greatly reduce the
 chance of mishap while performing corrosion
 removal.
   CORROSION REMOVAL TOOLS AND
            MATERIALS


• Common Materials And Hand Tools
• Power Tools
• Alternate Removal Methods
  COMMON MATERIALS AND HAND TOOLS

Materials and hand tools are classified as abrasive
   mat/cloth/paper, metallic wools, wire brushes and scrapers.
ABRASIVES & SANDPAPERS: The selection and use of
   any abrasive is determined by the type of metal and degree
   of corrosion damage.
Flint - used due to low cost, dulls and wears out quickly,
   normally a tan color
• Emery - mainly used for final polishing of metal due to it’s
   fine mineral face
• Aluminum Oxide - used on metal surfaces, fast and last
   longer than flint
• Silicon Carbide - sharp abrasive for wet or dry sanding on
   paint and metal
Aluminum oxide works better on softer metals such as
  aluminum and magnesium. Silicon is more effective on
  harder metals like ferrous alloys. These materials should
  be used primarily to remove mild to moderate corrosion
  and for surface polishing after corrosion removal.
Don’t overlook the common pencil eraser. It can be used to
  remove light corrosion from electrical contacts and printed
  circuit boards.
METALLIC WOOLS - Used to remove corrosion that is
 not tightly adhered to a metal surface.
         TYPE         GRADE                    USE
Very Fine                000     Final Smoothing

Fine                      0      Most Commonly Used

Medium                    1      General Purpose

Medium Coarse             2      Rough Work

Coarse                    3      Restoration

There are four major types of metallic wools:
Aluminum
Copper
Steel
Stainless Steel
Selecting the proper metallic wool looks easy at first glance.
  There is another consideration that comes into play here.
  You must know what type of metals you are working on.
  Steel wool is used on ferrous metals; aluminum wool on
  aluminum, aluminum alloys, magnesium and magnesium
  alloys; copper wool on copper, bronze and brass; and
  stainless steel wool on stainless steel. DO NOT use
  metallic wools which are not galvanically compatible with
  the metal surface being treated. Remember the chart on
  compatible metals? Using the incorrect metallic wool will
  only cause the corrosion to return in the near future.

When using metallic wool, always wear gloves and exercise
 caution - wool fibers are sharp!
WIRE BRUSHES - Come in a variety of sizes, shapes and
 are composed of different types of metal. The same rule
 applies to wire brushes and metallic wool - use a metal
 brush that is compatible with the metal you are treating.
 Wire brushes are used to remove heavy corrosion deposits.
 Thick, short bristles are used for rapid removal of heavy
 deposits, finer brushes for lighter jobs. NEVER use a
 brush with a bristle diameter greater than 0.010 inch
 because it can damage the metal you are treating.

Never brush sideways across another brush mark, this can
  cause unnecessary damage to the metal. After brushing a
  soft metal, polish the surface with a fine abrasive paper to
  remove brush marks.
SCRAPERS - Used primarily to remove heavy corrosion
  deposits in corners and crevices that cannot be reached.
  Due to gouges made by scrapers, the area will require
  further finishing.

FILES - Same as scrapers.
POWER TOOLS - Remove watches, rings, button shirt
  sleeves, tuck in loose clothing and always wear eye
  protection. Ensure work area is properly ventilated and
  wear a respirator. Be careful not to generate too much heat
  on the metal surface. It can change the bonding of metals
  making them vulnerable to intergranular corrosion.
  Remember to protect nearby equipment and clean up the
  entire area after work has been completed.



                       WARNING
Corrosion products of copper are highly toxic. Proper safety
  precautions must be taken to avoid inhalation or ingestion
  during corrosion removal. Personnel should wash hands
  before eating or smoking.
      ALTERNATE REMOVAL METHODS

There are several other methods available to remove severe
  corrosion. Workcenters in the 48IS will not perform these,
  but I will mention them briefly.
ABRASIVE BLASTING - Corrosion is blasted away using
  an abrasive driven by air pressure in excess of 125 pounds
  per square inch. C-E equipment should never be allowed
  to deteriorate to the point this is required. Steel antenna
  support structures may require this treatment.
CHEMICAL REMOVAL - Application of acid-based or
  rust conversion chemical. If left on equipment too long, it
  may eat into the metal being treated. Should be
  accomplished only by personnel with the proper training
  and equipment.
   CORROSION REMOVAL PROCEDURES

PREPARATION:
• Identify the extent of the corrosion and type of material to
  be treated. Then determine if the work can be
  accomplished at the workcenter level and the type of
  corrosion removal tools needed.
• Survey the area for safety hazards and take the appropriate
  precautions.
• Cover up and protect all equipment and facilities that could
  be damaged in the removal process.
• Gather all materials needed (to include protective
  equipment and safety observer).
• Consult the applicable TO for correct removal procedures,
  cautions or restrictions.
• Coordinate the work with Maintenance Control
CORROSION REMOVAL:
• Closely inspect your work - 100% of the corrosion must be
  removed.
• Use the appropriate materials to smooth the surface area
  and prepare it for the protective coating.
CLEANUP:
• Remove all dust, particles and corrosion residue from the
  treated equipment and surrounding area.
• Remove protective covers from other equipment and
  inspect for contamination. Clean as necessary.
• Wipe down the area from which the corrosion was
  removed with isopropyl alcohol.
• Properly dispose of used materials and put away tools.
• Return the equipment to operation and complete the
  correct documentation in CAMS.
      CORROSION TREATMENT
          PROCEDURES
SAFETY - Many materials used for corrosion treatment are
  both flammable and toxic. All products obtained through
  normal supply channels will have a Material Safety Data
  Sheet (MSDS). It is extremely important for you to follow
  all safety precautions when using corrosion treatment
  materials. Wear of respiratory protective devices, rubber
  gloves, apron and eye protection is a good idea if you are
  ever in doubt. Always wash hands thoroughly after
  working with these products and always before eating,
  drinking or smoking.
            PROTECTIVE FILMS
SEALANTS:
• POLYSULFIDE - Prevents moisture intrusion on
  equipment exposed to outside elements.
• ZRC AEROSOL SPRAY - General use sealant.
• ROOM TEMPERATURE VULCANIZING (RTV) -
  One of the most commonly used sealants.


                    WARNING
DO NOT use an RTV containing Acetic Acid. This RTV
 will cause serious corrosion on all metallic surfaces.
CORROSION PREVENTION COMPOUNDS (CPC):
CPCs are effective corrosion inhibitors, but never apply a
  CPC unless authorized by a TO. Consult Maintenance
  Support for assistance.

LUBRICANTS: Fill air gaps between moving parts and
  forms protective barriers against dirt, moisture and foreign
  materials thus inhibiting corrosion. Use only IAW the
  applicable TO.
VARNISHES: Provides a thin film that is resistant to
  moisture and fungus.

CONFORMAL COATINGS: Special protective
  compounds that conform to the contour of the material it is
  applied to. Many circuit boards have conformal coatings.
  Again, check the appropriate TO.

TOPCOATS: Paint. Always use the correct paint specified
  in your equipment TO.
LACQUERS & ENAMELS: Good for indoor use only.

POLYURETHANE: Perhaps the most effective topcoat
  made. Requires careful mixing and respiratory protection.
  (No we’re not talking about the type you buy at the
  hardware store.)
As you can probably tell, there are many types of protective
  films. Always check your equipment TOs as well as TO 1-
  1-689 and 1-1-691. Your Unit Corrosion Control Monitor
  in Maintenance Support can also offer assistance.

Once you have determined the appropriate protective film to
  use, always follow manufacturer application instructions
  and personal protective measures on the MSDS.
Remember corrosion prevention and control is everyone's
  responsibility. Wherever there is a metal surface, there
  could be corrosion.
   IT’S TIME TO TAKE THE
            TEST

                     GO TO:

P:\common\LS\LSK\corrosion training\corrosion test\

      Follow the instructions and Good Luck.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:395
posted:8/4/2011
language:English
pages:72