Simply unblocking I'd say.

That's one way of translating it.
Release of rust from screws, bolts etc


HTH

préparation pour le dégrippage des écrous

Reference TARIF DOUANIER;NOTEX CCD;38.19



(1)
TERM bold and nut release preparation



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Note added at 2002-02-21 14:19:41 (GMT)
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Well it is only \"release\" or

Termium defines degrippage as penetrating oil, with this explanation:
special type of oil
designed to release seized or
corroded parts

My can of WD-40, the leading anti-rust product in the US, says that it "penetrates and frees" rusted or corroded screws and bolts. "Dégrippage" is a noun that could either be describing an action, or naming a type of product. English prefers to use verbs to describe actions, hence "free," rather than "the freeing of," for instance. Otherwise, if you need a descriptive term for the type of product (rather than the action it performs), use Paula's "penetrating oil."

The following is from the WD-40 website (everybody has one of those nowadays!):

Welcome to WD-40 * Our Brands: WD-40 FAQs
... eliminate moisture-induced short circuits. PENETRATES: WD-40 loosens rust-to-metal bonds and frees stuck, frozen or rusted metal parts. LUBRICATES: WD-40's ...