There are many items that are no longer tracked by the corporation. If there is an audit they would rather get rid of these items than try to track them now. In addition, aside from audits this equipment will most likely be destroyed if they do find it.
Can it be taken for personal use without explicit permission from the company?
אָסוּר לִגְנֹב כָּל שֶׁהוּא דִּין תּוֹרָה. וְאָסוּר לִגְנֹב דֶּרֶךְ שְׂחוֹק אוֹ לִגְנֹב עַל מְנָת לְהַחְזִיר אוֹ עַל מְנָת לְשַׁלֵּם הַכּל אָסוּר שֶׁלֹּא יַרְגִּיל עַצְמוֹ בְּכָךְ:
According to the law of the Torah, it is forbidden to steal the smallest amount. It is likewise forbidden to steal in jest, or to steal with the intention of returning the object or paying for it. All this is forbidden, lest one may become addicted to it.
אֵיזֶה הוּא גַּנָּב זֶה הַלּוֹקֵחַ מָמוֹן אָדָם בַּסֵּתֶר וְאֵין הַבְּעָלִים יוֹדְעִים. כְּגוֹן הַפּוֹשֵׁט יָדוֹ לְתוֹךְ כִּיס חֲבֵרוֹ וְלָקַח מְעוֹתָיו וְאֵין הַבְּעָלִים רוֹאִין. וְכֵן כָּל כַּיּוֹצֵא בָּזֶה.
Who is a thief? One who takes a person's property secretly without the owner's knowledge, as when he puts his hand into someone's pocket and takes money out without the awareness of the owner, and so on.
It's apparent from the above, that one is not allowed to take something even if the owner doesn't need the product. While it might not say those words specifically, I believe it's obvious that if one is not allowed to take something from a store even if he has in mind to pay later, then obviously one cannot take something that might not be needed, unless there's explicit permission from the company.
The previous, accepted answer is too simplistic albeit the sources are true.
The main problem in your answer is to establish ownership because the main question here and in all other cases of monetary disagreements is who's called מוחזק of the stuff. There are two possible solutions:
The answer about stealing fits the first scenario but not the second (see the clarification below). The second scenario can be regarded generally as "אבידה מדעת" or "הפקר". It can be also divided into two sub-scenarios:
Once the stuff is declared as waste by the management it surely bears the status of "אבידה מדעת" and can be taken without their specific permission on every item.
Once the stuff is declared not usable but is not officially declared as abandoned, but everybody knows that it is - that's the tricky situation. This is similar to what the Gemmoarah discusses in BM: the questionable property such as fruits of a tree that fall outside the fence - are they still considered their owner's or אבידה מדעת.
There are different approaches to resolving such a situation:
Clarification on stealing (גניבה or גזל): It has two parts: the monetary (בין אדם לחבירו) which is a subject to repay and ethical (בין אדם למקום) which is the wrongful thought of stealing. So theoretically one who takes something legal (postfactum) but fells that's a steal also transgresses this commandment. On the other hand, if he takes it rightfully but he's proven that the item was not הפקר, he only transgresses the first part בשוגג and postfactum.
The fineprint: the last distinction applies to non-J, גזל גוי is forbidden only because of the second part, as it "deforms the Jewish soul", but the monetary part is forgiven, כמו אחד שלוח מקל מכלב.
