Removing corrosion from the barrel plate of IBM AT Model F keyboards

[troglotype]

Vintage IBM Model F keyboards often suffer from corrosion of the steel plate holding the barrels ("barrel plate"). People restoring Model Fs either leave the corrosion as it is or they repaint the barrel plate after sanding or sandblasting. In the case of AT Model Fs, both sanding and sandblasting, as well as chemical paint stripper or rust remover, will probably damage the non-removable plastic clips which hold the stabilizer wires on the barrel plate ("stabilizer clips"). While you might try to keep away from these, it is often the stabilizer clips and stabilizer wires that attract the most dirt and thus speed up corrosion. In other words: The most corroded areas are also the areas most susceptible to damage from removing corrosion.

I want to share a method that allows you to remove corrosion from the entire barrel plate without damaging the stabilizer clips. It is cheap and requires only a handful of things you probably have at home already


Before

IBM AT Model F – Corroded barrel plate (focus on stabilizer clips)

IMG_0822.JPG (2.91 MiB) Viewed 4509 times

After

IBM AT Model F – Cleaned barrel plate (focus on stabilizer clips)

IMG_0825.JPG (2.7 MiB) Viewed 4509 times

WHAT YOU NEED

• Vinegar. I used 6° white wine vinegar. I don't know what other kinds of vinegar work well. I'd probably stay away from aceto di balsamico.
• Aluminum foil. I used the sturdy kind, but the thinner kind should work as well.
• Eye protection. The process produces very little to no splatter, but if vinegar and specks of corrosion do get into your eyes, you might not like it.
• Latex gloves. You don't need them but they make the process easier on your hands.

WHAT YOU DO

1. Separate the barrel plate from all other parts of the keyboard. DO NOT use this method while the barrel plate is attached to any other part of the keyboard as this would damage the keyboard beyond repair.
2. Clean the barrel plate thoroughly with warm water and a suitable detergent. Because the keyboard I was restoring had been used in a print shop, there was a lot of greasy ink mixed in with the corrosion and I used a soda-based biodegradable detergent.
3. Wipe off excess water and let the barrel plate dry completely. You can use a moderate heat source, e.g. a hairdryer on a low heat setting, to speed up this step of the process. The drier the barrel plate, the greater the impact of the vinegar in the next step.
4. Soak the barrel plate in vinegar. You can immerse the entire barrel plate in vinegar or pour vinegar over just one part of the barrel plate at a time. Whichever you choose (I chose the latter), it is important to allow the corroded parts to soak up the vinegar for a few minutes.
5. Take aluminum foil amounting to about the size of a walnut and form it into a shape that allows you to hold it comfortably and get at the corrosion easily. This might be a wedge or a ball or even a "blade" – you will figure out what works in your case.
6. Use your self-made aluminum tool to remove corrosion. There is no need to use brute force. Small straight and circular motions, additional vinegar when necessary, and a bit of patience will bring the desired result.
7. To remove corrosion near or right on the edge of a barrel hole, form an aluminum "plug" slightly larger than the barrel hole and rotate it inside and over the hole.
8. Depending on the amount of corrosion, you might want to rinse and dry the barrel plate once or twice during the process.
9. Once your aluminum tool passes over the surface of the barrel plate without any resistance, you have probably removed all corrosion and some or all of the existing lacquer.
10. In a few places and especially around the stabilizer clips, corrosion might have penetrated beneath the surface of the barrel plate. In these places I used a small flathead screwdriver to break up the rust, added copious amounts of vinegar, let it soak, and started cleaning with the aluminum tool.
11. Once you have removed all corrosion, wash, rinse, and dry the barrel plate. You can now prepare the barrel plate for painting. The smooth surface makes it very easy to give it a light sanding.

IBM AT Model F – painted barrel plate (focus on stabilizer clips)

IMG_0837.JPG (1.64 MiB) Viewed 4509 times

[Engicoder]

Interesting method. Thanks for sharing it. Your results are fantastic. What paint did you use for the final finish?
I have used vinegar as well, but I am lazy so I usually just submerge the entire plate and leave it a few hours or overnight. Next day all the corrosion and black finish easily brushes off and you're done. Even seriously corroded plates come out pretty clean with the soak method.

[fohat]

It is all vastly easier when you remove the plastic clips and clean them separately, but it is inevitable that you will damage 5%-10% of them, so it is a risk if you don't have spares.

[troglotype]

What paint did you use for the final finish? [...] I have used vinegar as well, but I am lazy so I usually just submerge the entire plate and leave it a few hours or overnight. Next day all the corrosion and black finish easily brushes off and you're done.

I used Hammerite direct to rust metal paint. This is NOT the best choice. It didn't bond well in all places and I didn't wait long enough for it to dry properly. Because I used the thick replacement foam from Ellipse, many clamps were needed to join the two plates and they ended up damaging the paint job despite all the precautions. Regular interior metal paint probably works much better.

Great idea! Since this was my first restoration, I was hesitant to submerge the plate in vinegar for a long time.

[troglotype]

It is all vastly easier when you remove the plastic clips and clean them separately, but it is inevitable that you will damage 5%-10% of them, so it is a risk if you don't have spares.

I completely agree. Because this is my first restoration and I lack spare clips, I wanted to play it safe. It's the least invasive method, but certainly not the easiest or most effective one. I leave these to the pros.

[JP!]

I wish I could get some of those plastic clips or an elegant alternative.

[troglotype]

I wish I could get some of those plastic clips or an elegant alternative.

Maybe this would be an option (you can also produce your own, I guess):

https://www.modelfkeyboards.com/product ... tabs-pair/

[JP!]

I wish I could get some of those plastic clips or an elegant alternative.

Maybe this would be an option (you can also produce your own, I guess):

https://www.modelfkeyboards.com/product ... tabs-pair/

That's a good idea but I'm not quite sure how they stay in place. Also would be quite expensive to do something like a Model F AT.

[troglotype]

That's a good idea but I'm not quite sure how they stay in place. Also would be quite expensive to do something like a Model F AT.

Yes, that's the reason I made every effort NOT to damage them. In my case, sourcing replacements would take much more time (and funds) than using a slow and non-invasive method of cleaning.

[orihalcon]

I usually take all of the stabilizers out while I wire brush and repaint, then put them back in place after. Some boards have extra stabilizers like F107’s and those make good replacements for other boards, though the spacebar ones are unique, so I always cringe when those are broken :/

[fohat]

Often on my F-122 ANSI conversions there is little or no need to put back any of the tabs at all.

Unfortunately, over half of the Model Fs that have crossed my work bench had missing or damaged space bars anyway, so some mod (permanent tabs fabricated and epoxied down or some overlay such as fabricated sheet or 7/16" SAE washers) to allow the use of standard Model M space bars was in order.

That leaves only Backspace, Right Shift, and numpad 0 as candidates for re-using wire-stabilized keys, and stock Backspace and Right Shift will not match the style of modern replacements. Thus I often re-use only the numpad zero and even if I put back some of the tabs, those will be the only ones in use.

There is a good reason to re-install the space bar tabs only if you have a proper working Model F space bar and wire to be re-used.

All of the above pertains to the 122-key, 107-key, (and presumably the 77-key and 62-key -I have never seen these last 2 in real life) terminals and the F AT after the mod to install Alt keys. Unmodified XTs and ATs have that weird black under-carriage assembly so their space bars are in a league of their own.

[troglotype]

I usually take all of the stabilizers out while I wire brush and repaint, then put them back in place after

Out of curiosity: Is it possible to take out the stabilizer clips without damaging to the back of the barrel plate? On the keyboard I was restoring, the feet of the clips are "melted" in place, creating plastic "beads" on the back. One would have to sand off the beads to push the clips out toward the front. But since the coating on the back of the barrel plate was intact, I was hesitant to sand on that side.

[fohat]

If you push the tabs out (from back to front) with a small flat-head screwdriver (just small enough to go through the slot in the plate) you will usually end up with 1/3 to 2/3 of the "flange" still attached. That is usually enough to re-seat it.

To re-install, put a larger flat-head screwdriver into the "mouth" of the tab and force it back into the plate with the shaft of the screwdriver parallel to the barrel plate. This takes a pretty hard push, but you can usually get some or all of your remaining flange back through.

I usually re-install them when my paint is dry to the touch but not cured, in hopes that the paint will "glue" them in place. Anyway, I have never had one come up, so I think that the force fit is tight enough to keep them in place. And also, your paint has reduced the interior diameter of the slots by some tiny amount, so that probably helps too.