Hey guys.
I've bought a few different Male and Female headers, some Tin, and some Gold.
Initially I didn't even consider dissimilar metal problems, but when I finally received the headers in the mail and had them in-hand, the thought occurred to me.
How much of an issue is dissimilar metals in a ~5v Arduino environment?
I know corrosion takes a while, so perhaps it's only an issue in permanent builds?
It really depends on how much electrolyte is available, I think.
You won't have an issue. Gold is quite inert.
Interesting issue. Here is some advice from Intel from 1997 (summary: not a great idea):
http://advantagememory.com/Home_Page/support_link/faq/why_do_gold_and_tin_contacts_mak.htm
This is why the old advice of "reseating your boards" was given for failing ISA cards. The mechanical action of moving the contacts over the pads was enough to break the oxides that formed.
--
The QuadRAM shield: add 512 kilobytes of external RAM to your Arduino Mega/Mega2560
Ah, nothing like a mixed bag of replies!
This thread made me think "so what happens with gold-plated boards?" Why would you plate with Gold if you will be soldering with a Tin-based solder? I didn't realize that the gold plating is actually dissolved during the soldering process.
Panici:
Ah, nothing like a mixed bag of replies!
I wasn't going to answer as I assumed someone would give a more scientific answer somewhere.
Look around, there's loads of gold\tin mating going on, stuff is sold to be used in exactly this way (rightly or wrongly). You can get gold plated HDMI, SCART, RCA leads etc... that will all be mating with cheapo tin terminals. I've never seen one of these lead combos start to cause any problems after being plugged in for at least a matter of Months or even Years.
Bottom line - 'tis fine.
I guess you are planning to solder them. I hope you "sand" the soldering point.
Right now, I am soldering a steel wire - 12 gauge ( from a coat hanger ) to a 12 gauge copper wire ( from an old Air Conditionning electrical wires ) with the help of a smaller 22 gauge copper wire to attach it and solder together to make a DYI HD fractal antenna. Anything Goes. I am making 4 of them to make a bow-tie configuration diytvantennas.com
I have to make a good contact, so I sand the area where I will be soldering. I alway try to remove/sand the area where I will be soldering. If I do not do that, well the solder do not make a proper contact and it look like a cold solder joint. Even I have a PCB & DYI type board, I alway use a SOS steele wool to remove the oxidation.
Anyway, soldering gold with tin...YES it is possible, sanding the contact will help.
Techone, you should look into getting a bottle of liquid flux, that will help with cleaning as you solder as well.
Sanding is terribly agressive - it's appropriate for that painted coathanger wire, but keep it away from your PCBs.
As Crossroads says, a good flux is the solution. And, for large wires, an iron that has a large tip and will put out plenty of heat.
-j
Thank for the tip. I will look into it.
I use a SOS pad to clean a PCB board - my own DYI PCB. Clean nice. As for the large copper wire - the 12 gauge - I did use a "light" sanding - high grid. As for the coat hanger's, I use a low grid. I will look and buy the "flux"
What type of flux to buy ? hum..No idea :~ I know I can not use the flux for soldering copper pipes.
My favorite flux applicator is a flux pen - looks and works like a magic marker or paint pen, except it's flux that is dispensed. Kester is a big manufacturer of solders and fluxes.
There are various formulations of fluxes. I prefer a no-clean flux; it's less aggressive than others, but it doesn't leave a corrosive residue, either. If you don't use a no-clean flux, you need to clean the board (per the flux manufacturer's recommendations) to make sure the flux residue doesn't make your board corrode (and fail).
Google "kester no-clean flux pen".
-j
Thanks. I will look into it. I will check it up on the Net, check for prices and see the electronics store I goes to have it in stock. Thank for the good tip.
Radio Shack sells a Rosin paste in a can, and can be left on the board after soldering. I even treat boards with the flux after etching and cleaning to preserve the newly exposed bright copper from oxidization during storage.(I never etch just one board......never know when you will need another one)
If you want long-term reliability go with thick gold plating (its expensive but its the most reliable).
Using all tin-plated contacts has several issues - if a corrosive atmosphere then the metal corrodes (that means in a city or near the sea!) eventually - you cannot expect decades of reliable operation without regular maintainance.
Also tin-plate has the tin-whisker problem. Thin whisker crystals of tin (or zinc) grow from the surface over a long timescale, eventually leading to shorts. Its a bizarre phenomenon that's not well understood. Within a whisker of failure | Research and development | The Guardian, NASA Goddard Tin Whisker Homepage
For normal use I wouldn't worry except to say "use gold if a corrosive / salty environment". Most issues can be managed by cleaning connectors every few years.
Some people say mixing tin and gold is less reliable than tin/tin IIRC.
@all in this tread and all newbees with soldering
I just bought MG Rosin Flux. Since I have to figure out how to apply to my joint/lead, I use a q-tip, soak with the rosin flux, wet the joint/lead and ...... 
IT WORK LIKE A CHARM !!! The solder joint are very nice and propely done right. Except the dificult joint that I have a hard time with, I light scrap the lead and re-do the soldering.
Now it is more fun to solder...
Thanks guys for this tip. I am gratefull for the tip. Thank you. 
Yup, its all about having the right tools...
The tin whiskers article was very interesting reading. I too abhore leadfree solders, but from the standpoint of the lack of plastic state during cooldown that 60/40 solder exhibits. I never get a grey joint with 60-40.