Got a temperature regulated solder iron, always had the temp set to 350C. Used the wet sponge after every solder job to clean the tip. Used a 60/40 rosin core 0.6mm solder. After week of use, when turning it on again I noticed the stock tip only had few areas where the solder would stick to. The areas were visible, they had dull metallic look, the rest areas were darker. Tried cleaning with wet sponge, made no difference. Finally had to use very fine sandpaper. After that no part of the tip was usable anymore. But the surface was metallic, not copper color so I don't think I sanded away all the tip cover.
Is there any explanation for this?
Replaced the tip with a new one which came with the iron. Solder sticks to it well, but I don't know how long this one will last. Here are pictures of how a 60/40 solder looks on it (wanted to tin the tip). Very odd coloring. Does this give any explanation?
Not a professional, so didn't get an expensive quality solder station, but this one wasn't cheap either and had a iron holder, replaceable tips and temperature knob. The iron itself seems to work fine.
Best Answer
There are definite quality differences between tips from different vendors, the base material used may differ (steel, iron, copper, silver) - Though I don't generally support silver as it gives near to no benefits over a well coated copper one, I have recently posted an answer on that here. But there is also difference in coating quality and even type and some last longer than others.
What you should never do with any coated tip (99% of them) is clean them with hard abrasives. Very cheap tips might not even like those steel mesh sponges, but if your tip is that cheap...
Which brings me to another piece of advise: Try if you like a steel mesh sponge, many outlets have them at a buck or two, they need no wetting and if you can get the movement right easily they clean well enough, but at 350degrees offer a much lower chance of cracking of the coating. But those are not for everyone and in many cases a lightly wet sponge (not soaking! Very easy to crack the coating when it's soaked) cleans better.
To restore a coating there are things like "Tip Activator" that you can use. A small $8 can from cooper tools / weller can last you dozens of uses and for most people you only need it once per year, or even longer for each tip you use regularly. It basically cleans a little and leaves a bit of coating layer extra behind. But never use it on a new tip of well coated quality. As with anything, a cheap home solution to add coating or such is always less good than a good factory coating.
You may be able to restore your damaged tip to sort of working order with tip-activator as well, I have used it to get horrible uncoated stainless steel tips to usable for a month or two, so it's worth a try.
Usually tip-activator works best when you put in a tip at 150 ~ 200 degree C, but the datasheet or booklet that comes with it will say how to use it.