Oftentimes, the corrosive material from the batteries transfers to whatever device you were using the batteries to power. Unless effectively treated, the corrosion will return from the contact points to whatever batteries you might use to replace the corroded ones with. You can very often completely remove the corrosive material from the device's contact points and area around same by using clear vinegar. Apply a vinegar wet cotton swab to get around the nooks and crannies of the contacts and adjacent areas. Use it generously as it should evaporate fairly quickly. You can also use an air can to dry the area of application and force the residue out of corners and cracks. Once I figured out that vinegar did the trick, I have been able to salvage a number of good quality instruments and devices (flashlights, remotes, etc.).
