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Posted: 5/7/2004 3:05:04 AM EST
Looks like some of the older CD's aren't holding up too well. This is pretty disturbing to say the least. We were lead to believe they were a timeless storage system.

www.dailystar.com/dailystar/business/20871.php

Wonder if this was just one brand or if it's industry wide.
Link Posted: 5/7/2004 3:05:57 AM EST
Another victim of hype.
Link Posted: 5/7/2004 3:08:25 AM EST
Well don't that suck
I just finished the huge change over from tape to DVD .
Don't it figure.
Link Posted: 5/7/2004 3:11:36 AM EST
Link Posted: 5/7/2004 3:20:40 AM EST
[Last Edit: 5/7/2004 3:21:03 AM EST by wetidlerjr]

Originally Posted By cyanide:
Well don't that suck
I just finished the huge change over from tape to DVD .
Don't it figure.



Gee, and to think you might lose all your Bobbsey Twins and Sesame Street movies !
Your mommy will beat your ass, again !

Link Posted: 5/7/2004 3:41:00 AM EST
Well ain't that just freakin' lovely.
Link Posted: 5/7/2004 3:43:24 AM EST
great
Link Posted: 5/7/2004 4:13:04 AM EST

Originally Posted By wetidlerjr:

Originally Posted By cyanide:
Well don't that suck
I just finished the huge change over from tape to DVD .
Don't it figure.



Gee, and to think you might lose all your Bobbsey Twins images.amazon.com/images/P/0448090716.01.LZZZZZZZ.jpg and Sesame Streetpbskids.org/sesame/images/cookie_03.gif movies !
Your mommy will beat your ass, again !




It was the homo insults wasn't it.

Link Posted: 5/7/2004 4:16:50 AM EST
This is why I've put over 500 gigs of storage space in my PC and backed up all of my CDs in lossless FLAC format. I'm still working on ripping them all, and plan on some day scanning the covers/liner notes.
Link Posted: 5/7/2004 4:20:31 AM EST

Originally Posted By cyanide:

Originally Posted By wetidlerjr:

Originally Posted By cyanide:
Well don't that suck
I just finished the huge change over from tape to DVD .
Don't it figure.



Gee, and to think you might lose all your Bobbsey Twins images.amazon.com/images/P/0448090716.01.LZZZZZZZ.jpg and Sesame Streetpbskids.org/sesame/images/cookie_03.gif movies !
Your mommy will beat your ass, again !




It was the homo insults wasn't it.




Nope ! Since I''m not a HOMO, I am not insulted by being called one. I am secure in who I am and my mommy does not beat my ass like your mommy does you.
On the other hand, YOU seem to have a fixation on homosexuals and I think that says a lot about you and what you fear.
By the way, when will you be here for the shootzenfest ?
Link Posted: 5/7/2004 4:29:47 AM EST
Yep, in the 80's we were definately lead to believe that cd's would last forever.

Perhaps someone could provide better info, but I read a while back, (for those who use CD/r) Most cdrs are only good for about 20-25 years. The cdr disks that are made in the Japaneese chemical facility use a different chemical and will last for 80-100 years.
Link Posted: 5/7/2004 4:35:54 AM EST
I've got CD's from 1983 that still play flawlessly.... 21 years and counting.
Link Posted: 5/7/2004 4:45:14 AM EST
I wonder if storing them in something such as an ammo can will help increase their life expectancy
Link Posted: 5/7/2004 4:45:52 AM EST
I have plenty (hundreds) of 1980's CD's that still play perfectly (I can't think of any that don't). Also, I remember reading about this possibility back in the 1980's. The concensus then was that they wouldn't last forever, but certainly MUCH longer than the typical LP album of the day under normal use. Just take care of them, and don't bend them.
Link Posted: 5/7/2004 4:46:07 AM EST
Glad I switched from paying to stealing downloading from Kazaa two years ago. All that unwasted money... going toward gun stuff.

Link Posted: 5/7/2004 5:25:23 AM EST

Originally Posted By pathfinder74:
Glad I switched from paying to stealing downloading from Kazaa two years ago. All that unwasted money... going toward gun stuff.




If it's a cd that I like, I have no problem whatsoever with paying for it, I still download it first to listen to it, because I refuse to pay 16 bux for 1 good song. Or if the artist is some liberal POS, i wont support them either.
Link Posted: 5/7/2004 6:34:35 AM EST
CD Rot is a bunch of BS. DVD Rot is real, but very limited. People heard of DVD rot, and started blaming that for their CD failures when that isn't possible.

DVD Rot is real, and is limited to select movies produced by "Warner Advanced Media Organization" a couple years ago. Several batches of those movies had a lamination failure due to the production process they were using. This has since been corrected. You can find a list of the movies on various web sites. This rot would spread from the point of failure and over time cause increasing failures when playing the disc.

DVD's have a chemical layer for their media, while CDs are aluminum. We are firearms people here so we know the properties of aluminum. Aluminum oxidizes rapidly and then stops. It does not spread and rust like steel. A small scratch in the lamination will cause oxidation in the aluminum underneath the scratch, but that will be the end of it. Only the area contacting the oxygen will be effected. It will not spread with time. This guy obviously stored his discs poorly and they were scratched, or he forgot they had the problems originally. We are all guilty of setting CDs down upside down when not in a case in order to prevent getting the playing side dirty or scratched. The downside is that the non-playing side is where the data is, and scratches there are permanent and can't be removed.

Eventually, the plastic and laquer will break down and both DVD's and CD's will fail, but we are talking centuries here, not decades.
Link Posted: 5/7/2004 7:40:50 AM EST

Search the download sites for a free download of CDRID, the program the CD-R manufacturers and sellers hate so much.

It tells ya if the CD-R uses short-term or long-term ink dyes. The short-term dyes usually last as little as 2 weeks or as much as 2 years, before they have broken down enough to not be readable.

The long-term archieval dyes are believed to have at least a 100 year life span. Very very few CD-Rs use it and they can be hard to find. Maxwell Pro is long term. Fuji CD-Rs in individual cases are, but those in bulk packs are not. All Sonys were long term, now none are. HPs were long term when I could find them. Every other brand I have tested used the short-term type. You have to test every box you get because you never know when they will pull a switch on you.

CD-RWs that use metal instead of ink have different ins and outs.

The commercial music CDs you buy do not use dyes, they are pressed with the music already on them so are not subject to this.

Link Posted: 5/7/2004 7:48:55 AM EST


Nothing lasts forever.
Link Posted: 5/7/2004 8:16:15 AM EST

I forgot to mention Kodak CD-Rs. Here is a link explaining more about Kodak CD-R longevity:
www.kodak.com/global/en/service/faqs/faq1632.shtml

"These accelerated ageing studies on KODAK CD-R Ultima media, considering the effect of temperature and humidity, indicate that its data lifetime is well in excess of the warranted lifetime of 100 years if the disc is maintained in a normal office or home environment (temperature less than or equal to 30°C, relative humidity less than or equal to 50%). No other brand beats KODAK CD-R Ultima media for stability. "
Link Posted: 5/7/2004 8:31:59 AM EST

CD Rot is a bunch of BS.

It's not. Half of my CD's made before 1988 quit working by summer of 1991. They were stored in my house that I didn't have A/C in until after that. The aluminum layer disappeared. You could see through the CD's in places where the aluminum look like it evaporated. I have a couple where over 75% of the metal is gone. On a few of the ones I have that quit, the plastic didn't seal the aluminum around the edges and most of them have quit working. Also, I've been working on sound systems in churches on and off for 15 years, and it used to be that all of the CD's worked, but now I'm seeing more and more older ones that have spots you can see through. It might be related to humidity, because I have two relatives with huge (>5,000 CD's) collections. The one in Florida has major problems with CD longevity for pre-1988 (or so) CD's and the one in Arizona doesn't.

I've been making a little money on the side converting CD collections to FLAC (lossless). That is a good thing to do. I also offer off-site storage and access via the Internet to the backups. For $90 you can get a 160 Gbyte harddrive and backup about 500 CD's. I have a CD tower at work with 10 CD drives so I can do 10 at a time. I've converted 6,000 or so, and I've found about (wild guess) about 30 that even my good Plextor drive can't read even though they weren't scratched.z
Link Posted: 5/7/2004 8:47:50 AM EST

Originally Posted By Bob243:

Originally Posted By pathfinder74:
Glad I switched from paying to stealing downloading from Kazaa two years ago. All that unwasted money... going toward gun stuff.



Or if the artist is some liberal POS, i wont support them either.



Isn't that the majority? not counting the bulk of CW.
Link Posted: 5/7/2004 8:54:05 AM EST
We have always known CDs won't last forever, it's just a mystery how long that actually is.

By the way, I was watching Modern Marvels the other day about consumer electronics I think... they had a guy talking about DVDs and was telling about how much better they are than tapes. His big selling point was that they are *more durable* than VHS tapes. He grabs a tape and says "See look at this" while he opens the hood and starts yanking the tape out and ripping it, then kind of smashes up the cover. Then he grabs a DVD and says "Now look at this!" and gently bends the DVD back and forth. Um, yeah whatever. Give it to my 3 year old kid and it will be destroyed within 60 seconds. He has never wrecked a tape, because he's not trying to do it on purpose. But unless you handle a CD or DVD very carefully it gets all scratched up. He'll take the DVD out of the cover and slide it around on the ground. Bye bye DVD!!
Link Posted: 5/7/2004 8:55:13 AM EST

Originally Posted By zoom:

CD Rot is a bunch of BS.

It's not. Half of my CD's made before 1988 quit working by summer of 1991. They were stored in my house that I didn't have A/C in until after that. The aluminum layer disappeared. You could see through the CD's in places where the aluminum look like it evaporated. I have a couple where over 75% of the metal is gone. On a few of the ones I have that quit, the plastic didn't seal the aluminum around the edges and most of them have quit working. Also, I've been working on sound systems in churches on and off for 15 years, and it used to be that all of the CD's worked, but now I'm seeing more and more older ones that have spots you can see through. It might be related to humidity, because I have two relatives with huge (>5,000 CD's) collections. The one in Florida has major problems with CD longevity for pre-1988 (or so) CD's and the one in Arizona doesn't.

I've been making a little money on the side converting CD collections to FLAC (lossless). That is a good thing to do. I also offer off-site storage and access via the Internet to the backups. For $90 you can get a 160 Gbyte harddrive and backup about 500 CD's. I have a CD tower at work with 10 CD drives so I can do 10 at a time. I've converted 6,000 or so, and I've found about (wild guess) about 30 that even my good Plextor drive can't read even though they weren't scratched.z



I hope you're not counting on the hard drive not going bad...!
Link Posted: 5/7/2004 8:55:30 AM EST
I want some of that aluminum you are talking about.

I have worked on aluminum aircraft structures for over 21 years in the military and in the civilian world. If you don't stop aluminum from corroding once it has started you will end up with a nice pile of white powder.




Originally Posted By gunman0:
We are firearms people here so we know the properties of aluminum. Aluminum oxidizes rapidly and then stops. It does not spread and rust like steel.

Link Posted: 5/7/2004 9:32:45 AM EST
Link Posted: 5/7/2004 9:46:00 AM EST

Originally Posted By pathfinder74:

Originally Posted By Bob243:

Originally Posted By pathfinder74:
Glad I switched from paying to stealing downloading from Kazaa two years ago. All that unwasted money... going toward gun stuff.



Or if the artist is some liberal POS, i wont support them either.



Isn't that the majority? not counting the bulk of CW.



Unfortunately, yes.
Link Posted: 5/7/2004 9:55:33 AM EST

Originally Posted By Aimless:
Part of the problem is that most people believe that it's the clear underside of the CD that is fragile, when in fact it's the label side. Scratches on the underside have to be fairly deep to cause skipping, while scratches on the top can easily penetrate to the aluminum layer.




I've been telling people that for years. NEVER LAY A CD OR DVD DOWN UPSIDE DOWN! Label is always up!
Link Posted: 5/7/2004 10:19:43 AM EST

Originally Posted By zoom:

CD Rot is a bunch of BS.

It's not. Half of my CD's made before 1988 quit working by summer of 1991. They were stored in my house that I didn't have A/C in until after that. The aluminum layer disappeared. You could see through the CD's in places where the aluminum look like it evaporated. I have a couple where over 75% of the metal is gone. On a few of the ones I have that quit, the plastic didn't seal the aluminum around the edges and most of them have quit working. Also, I've been working on sound systems in churches on and off for 15 years, and it used to be that all of the CD's worked, but now I'm seeing more and more older ones that have spots you can see through. It might be related to humidity, because I have two relatives with huge (>5,000 CD's) collections. The one in Florida has major problems with CD longevity for pre-1988 (or so) CD's and the one in Arizona doesn't.

I've been making a little money on the side converting CD collections to FLAC (lossless). That is a good thing to do. I also offer off-site storage and access via the Internet to the backups. For $90 you can get a 160 Gbyte harddrive and backup about 500 CD's. I have a CD tower at work with 10 CD drives so I can do 10 at a time. I've converted 6,000 or so, and I've found about (wild guess) about 30 that even my good Plextor drive can't read even though they weren't scratched.z



It must be the humidity. I have a 1,000 or so CD's from the 80's and they all are fine. I don't know of anyone personally that has had the problem you describe. Does the FLAC compression really not loose any quality? I have never tried it.
Link Posted: 5/7/2004 11:48:46 AM EST
It's a long read, this is what I used as a lecture guide when I taught corrosion control to my US Navy students.

FORMS OF CORROSION
Corrosion may occur in several forms, depending upon the specific function, size, shape and type of metal involved. Atmospheric conditions and the presence of corrosion-producing agents are also factors in the development of corrosion. The types of corrosion described in this section are the more common forms found on aircraft structures and SE.

This text uses the most commonly accepted terms that describe the various types of corrosion.

Uniform (Direct) Surface Attack
The surface effect produced by the direct reaction of a metal surface with oxygen in the air is a uniform etching of the metal. The rusting of iron and steel, the tarnishing of silver, and the general dulling of aluminum surfaces are common examples of surface attack. On aluminum surfaces, if the surface attack is allowed to continue, the surface will become rough and eventually frosted in appearance.

Pitting Corrosion
The most common effect of corrosion on aluminum and magnesium alloys is called “pitting.” The primary cause of pitting is the variation in structure or quality between areas on the metal surface in contact with a corrosive environment. Pitting corrosion is first noticeable as a white or gray powdery deposit, similar to dust, which blotches the surface. When the superficial deposit is cleaned away, tiny pits or holes can be seen in the surface. They may appear as shallow indentations or deep cavities of small diameter. Pitting may occur in any metal, but it is particularly characteristic of aluminum and magnesium.

Crevice Attack or Concentration Cell
Concentration cell corrosion is actually a form of pitting corrosion. Concentration cell corrosion is caused by the difference in concentration of the electrolyte or the active metal at the anode and cathode. When there are concentration differences at two different points in an entrapped pool of water or cleaning solution, anodic and cathodic areas may result. This results in the anodic area being attacked.
Areas where there are crevices, scale, surface deposits, and stagnant water traps are prone to this type of attack. Concentration cell corrosion is controlled and prevented by avoiding the creation of crevices during repair work. It is also controlled with sealants and caulking compounds that eliminate voids that trap water.

Intergranular Attack, Including Exfoliation
All metals consist of many tiny building blocks called “crystals” (sometimes called grains). The boundaries between these crystals are commonly called “grain boundaries.” Intergranular corrosion is an attack on the grain boundaries of some alloys under specific conditions. During heat treatment, these alloys are heated to a temperature that dissolves the alloying elements. As the metal cools, these elements combine to form compounds. If the cooling rate is slow, they form at the grain boundaries. These compounds differ electrochemically from the material adjacent to the grain boundaries, and they can be either anodic or cathodic to the adjoining areas, depending upon their composition. The presence of an electrolyte results in attack of the anodic area. This attack can be rapid and exist without visible evidence. As the intergranular corrosion progresses to the more advanced stages, it lifts the surface grain of the metal. This is caused by the force of expanding corrosion products at the grain boundaries just below the surface.

This advanced attack is called exfoliation. At this point, it can be seen by maintenance personnel. Correction of such serious corrosion is vital to aircraft safety. The insidious (sneaky) nature of such an attack can seriously weaken structural members before the volume of corrosion products accumulate on the surface and the damage becomes apparent. Metal that has been properly heat-treated is not readily prone to intergranular attack. However, localized overheating, such as could occur from welding and fire damage, can make metal prone to attack. If the intergranular attack has not penetrated so far as to impair structural strength, correction as outlined in the applicable structural repair manual (SRM) can restore an aircraft to flight status.

Dissimilar Metal Corrosion
The terms galvanic or dissimilar metal corrosion are applied when accelerated corrosion of metal is caused by dissimilar metals being in contact in a corrosive medium, such as salt spray or water. Dissimilar metal corrosion is usually the result of a faulty design or improper maintenance practices. You To keep these metals from coming in direct can usually recognize it by the presence of a buildup contact with each other, aircraft and support of corrosion at the joint between the metals. For equipment manufacturers use a variety of separating example, aluminum and steel materials riveted materials. Such materials include plastic tape, sealant, together in an aircraft wing form a galvanic couple if primer, washers. and lubricants. These materials keep moisture or contamination is present. When aluminum corrosion to a minimum. These separating materials pieces are attached with steel bolts or screws, galvanic must remain intact and be replaced, restored. or corrosion can occur around the fasteners.

To keep these metals from coming in direct can usually recognize it by the presence of a buildup contact with each other, aircraft and support of corrosion at the joint between the metals. For equipment manufacturers use a variety of separating example, aluminum and steel materials riveted materials. Such materials include plastic tape, sealant, together in an aircraft wing form a galvanic couple if primer, washers. and lubricants. These materials keep moisture or contamination is present. When aluminum corrosion to a minimum. These separating materials pieces are attached with steel bolts or screws, galvanic must remain intact and be replaced, restored. or corrosion can occur around the fasteners (fig. 4-12). repaired as needed

Some metals are more active than others. The degree of attack depends upon the relative activity of the two surfaces in contact. The more active or easily oxidized surface becomes the anode and corrodes. In plated metal, the possibility of dissimilar metal corrosion becomes a factor only if there are defects in the plating. Moisture penetrates and galvanic cells form because of these defects.

Stress Corrosion
Stress corrosion is caused by the combined effects of tensile stress and corrosion. Stress may be internal or applied. Internal stresses are produced by nonuniform deformation during cold working, by unequal cooling from high temperatures during heat treatment, and by internal structural rearrangement involving volume changes. Stresses set up when a piece is formed. Stress induced by press-and-shrink fits and those in rivets and bolts are examples of internal stresses. Concealed stress is more important than design stress because it is difficult to recognize before it exceeds the design safety factor. The magnitude of the stress varies from point to point within the metal.
Stresses that approach the yield strength of the metal promote stress cracking (visible at this point), but failure can occur at lower stresses. Most often, stress cracks are not visible to the naked eye and are discovered in the nondestructive inspection (NDI) process.

Fatigue Corrosion
Fatigue corrosion is a special kind of stress corrosion. It is caused by the combined effect of corrosion and stress applied in cycles to a component. An example of cyclic stress is the alternating loads to which the reciprocating rod on the piston of a hydraulic, double-acting, actuating cylinder is subjected. During the extension stroke, a compression load is applied. During the retracting or pulling stroke, a tensile or stretching load is applied. Fracture of a metal part due to fatigue corrosion commonly occurs at a stress far below the fatigue limit in a laboratory environment, even though the amount of corrosion is unbelievably small. This is why protection of parts subject to alternating stress is particularly important in any environment.

Fretting Corrosion
Fretting corrosion is a limited but highly damaging type of corrosion. It is caused by a slight vibration, friction, or slippage between two contacting surfaces that are under stress and heavily loaded. It is usually associated with machined parts. Examples of these parts are the area of contact of bearing surfaces, two mating surfaces, and bolted or riveted assemblies. At least one of the surfaces must be metal. In fretting corrosion, the slipping movement on the contacting surface destroys the protective films that are present on the metallic surface. This action removes fine particles of the basic metal. The particles oxidize and form abrasive materials, which further agitate within a confined area to produce deep pits. Such pits are usually located in an area that increases the fatigue failure potential of the metal. Early signs of fretting corrosion are surface discoloration and the presence of corrosion products in lubrication. Lubrication and securing the parts so that they are rigid are effective measures to prevent this type of corrosion.

Filiform Corrosion
Filiform corrosion consists of threadlike filaments of corrosion known as underfilm. Metals coated with organic substances, such as paint films, may undergo this type of corrosion. Filiform corrosion occurs independently of light, metallurgical factors, and microorganisms present. It takes place when the relative humidity of the air is 78 to 90 percent and when the surface is slightly acidic. Although the threadlike filaments are visible only under clear lacquers or varnishes, they also occur under opaque paint film. Filiform corrosion can attack steel, aluminum, and magnesium.

Microbiological Corrosion
Microorganisms contained in seawater can be introduced into fuel systems by contaminated fuel.
These fungus growths attack the sealing material used on integral fuel tanks. They can cause corrosion of aluminum, probably by aiding in the formation of concentration cells. Residues from biological growth tend to clog fuel filters and coat fuel quantity probes. Fuel quantity probes thus coated give erroneous readings. Also, moisture aides in the growth of fungi and microorganisms in avionic equipment.

Aluminum Aluminum and its alloys are used many places in aircraft construction, including ejection seats, chassis structures in avionic equipment, and the skin of the aircraft.

Because of its wide use, you must be able to recognize and take the proper corrective action whenever corrosion is detected or suspected.

Aluminum and its alloys are subject to a wide range of corrosive attack, varying from general etching of the surfaces to penetrating attacks along the internal grain boundaries of the metal.

The corrosion products appear as white-to-gray powdery deposits that have greater volume than the original metal. In its early stages, aluminum corrosion is evident as a general etching, pitting, or roughness of the surface. The surface attack progresses quite slowly at first; however, the attack will accelerate if the corroding material is not given immediate attention.

Paint coatings mask evidence of corrosion, but because the corrosion products have a greater volume, corrosion will show up as blisters, flakes, chips, lumps, or other irregularities in the paint coating. Often, white or gray streaks of corrosion products become readily apparent at breaks in the paint film. Maintenance personnel should investigate such signs further to determine the extent that corrosion has progressed.

There are three types of aluminum surfaces insofar as corrosion removal is concerned. They are clad, anodized, and exfoliated aluminum surfaces.

Clad Aluminum Surfaces.
Pure aluminum has considerable corrosion resistance compared to aluminum alloys. but it has little or no structural strength. An extremely thin sheet of pure aluminum laminated onto each side of an aluminum alloy sheet improves the corrosion resistance with little impairment of strength.

The trade name of this aluminum laminate, as originated by the Aluminum Company of America, is Alcad. From this trade name the adjective clad and the verb cladding have been derived.

An example of clad aluminum is the surface of unpainted aircraft. Not all aircraft sheet aluminum is clad, especially those alloy sheets from which small brackets, gussets, and fittings are made. The pure aluminum is very soft, and fabrication processes would severely damage or destroy the clad surfaces.

To remove corrosion from clad surfaces, the corroded areas should be hand polished with MIL-P-6888 metal polish. It effectively removes stains and produces a high-gloss, lasting polish on unpainted clad surfaces. During the polishing operation, you should take care to avoid mechanical removal of the protective clad layer and exposure of the more susceptible, but stronger, aluminum alloy base.

If there is any superficial corrosion present, you should treat it by wiping down the surface with an inhibitive material, such as the Chemical Surface Films for Aluminum Alloy, available under specification MIL-C-81706.

Anodized Aluminum Surfaces.
Nonclad aluminum alloys are the primary type of aluminum used on naval aircraft. Anodizing is the most common surface treatment of nonclad aluminum alloy surfaces.

In anodizing aluminum alloys, the alloy sheet or casting is the positive pole in an electrolytic bath in which an oxidizing agent produces an aluminum oxide film on the metal surface.

This aluminum oxide is naturally protective, and anodizing merely increases the thickness and density of the natural oxide film. When this coating is damaged in service, it can only be partially restored by chemical surface treatments.

Therefore, when processing anodized surfaces, including corrosion removal, you should avoid destruction of the oxide film.

Aluminum wool (nylon webbing impregnated with aluminum oxide abrasive) or fiber bristle brushes are the approved tools for cleaning anodized surfaces.

The use of steel wool, steel wire brushes, or harsh abrasive materials on aluminum surfaces is prohibited. A buffed or wire brush finish produced by any means is also prohibited.

Otherwise, anodized surfaces are treated in much the same manner as other aluminum finishes.

Exfoliated Surfaces.
As previously described, exfoliation is a separation along the grain boundaries of metal and is caused by intergranular corrosion.

More severe procedures must be used when intergranular corrosion is present. All corrosion products and visible delaminated metal layers must be removed by mechanical means to determine the extent of destruction and to evaluate the remaining structural strength of the component.

Maintenance personnel use metal scrapers, rotary tiles, and other tools to assure that all corrosion products are removed and that only structurally sound aluminum remains.

Maintenance personnel should inspect the area with a 5- to 10-power magnifying glass or use a dye penetrant to determine if all unsound metal and corrosion products have been removed.

When all corrosion products have been removed, maintenance personnel should blend or smooth out any rough edges, even if it involves the removal of more metal. Grinding, where required, is best done by using abrasive nylon wheels into which tiny particles of aluminum oxide abrasives have been impregnated.

Chemical treatment of exposed surfaces is applied in the same manner as any other aluminum surface. An aeronautical engineer should evaluate any loss of structural strength in critical areas.

This is particularly true if the damage exceeds the permissible limits established in the structural repair manual for the aircraft model involved.
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