I'm looking to replace some nibs I ruined, and in the meantime I need to store what's left for a while.
How should I go about preparing them for storage? Is there a difference between storing cartridge pen and dip pen nibs I should know?
There are a couple of things you need to consider before we look at storage options.
When you are done using your nibs you should ensure that you medium is removed and clean before you store it. Most people suggest just using room temperature water or more specifically distilled water (that would have less mineral build up that would being stuck inside the workings of the pen). Ink is obviously easier to clean before it has set.
More on this from Levenger.com
Remember that rust begets rust. You want to be sure that the nibs / cartridge nibs are free of rust before you go to store them. This is especially true if you intend to store your nibs together in close proximity. Enough rust will render the nib useless.
Baking Soda Paste
For simple surface rust you can make a paste from baking soda and water and use a toothbrush to gently work the surface to remove the rust. Again, using water to clean the surface one done.
There are more tactics to removing rust, like vinegar or a molasses bath, but given that there are hard to restore if the rust is bad you should only have to worry about simple surface rust.
One area where people seem a little divided is on storage of nibs. Particularity when it comes to storing nibs together where they can touch or completely segregated from each other.
Storage options are numerous. Some styles worth mentioning
Other storage considerations
By cartridge I presume you mean cartridge calligraphy pens and/or their nibs. The main difference when it comes to storage of nibs is that usually cartridge (fountain) calligraphy pen nibs are stainless steel and dip pen nibs are not. So the main concern will be with moisture/damp as the dip pen nibs will try to corrode, but I would store both in a dry place anyway. If the storage is likely to be for an extended period I would do what the manufacturers do and oil the dip pen nibs before storage (and remember to remove the oil before using).
I presume you will have cleaned and dried dip nibs after use. If not, remove from holder soak and use a tooth brush to remove any residual ink. If you have dried ink residue that does not loosen on soaking in water you need to use an appropriate solvent, usually some form of alcohol, in the UK methylated spirit would be my first choice, isopropyl alcohol my next ... Then dry after cleaning.
One really ought to do the same with the nib and feed of a cartridge pen, but it is more troublesome to pull the nib and feed for cleaning. Also flushing a cartridge pen (if you have the materials to do it) will not remove all of the ink residue from the nib and feed, so before long term storage you should pull the nib and feed for cleaning. (There should be no need to oil a stainless steel nib.)
I recently acquired a used fountain pen that had been stored inked and it had serious corrosion on the back of the nib, even though it was stainless steel, and nasty deposits blocking the feed. Fortunately I could junk both as I had bought it as a new home for a custom grind italic nib with feed that had lost their original home :)
There seems to be a trend to put manga G dip pen nibs in fountain/cartridge pens among some fountain/cartridge pen users. If you have such a pen the nib should be treated as a dip pen nib for storage purposes, and probably should be pulled and cleaned between every use anyway.