The phrase "as a pledge for" is correct and usable in written English.
It can be used when referring to something that serves as a guarantee or assurance for a promise or commitment.
Example: "He offered his watch as a pledge for the loan he needed."
Alternatives: "as a guarantee for" or "as a security for".
The American Dream began as a pledge for equality rather than as a dream of supremacy and 'making it big'.
The enormous sum of 15 talents of silver was deposited in Athens as a pledge for their safe restitution.
This property may be constituted as a pledge for enemy liabilities under the conditions fixed by paragraph 4 of the Annex hereto.
"I am encouraged by this choice, viewing it as a pledge for a church of simplicity and of ecological ideals," said Leonardo Boff, a founder of liberation theology.
Distress, in law, process that enables a person to seize and detain from a wrongdoer some chattel, or item of personal property, as a pledge for the redressing of an injury, the performance of a duty, or the satisfaction of a demand.
He also directed state grants of at least $150,000 — with a pledge for as much as $500,000 more — to the hospital over the next two years, a period that overlapped substantially with his wife's employment there from 2002 to 2005.
What began as a pledge task for Lambda Chi Alpha (LCA) in 1958 has become permanently etched, not only into the bridge, but into MIT lore as well.
Prosecutors are investigating the death as a pledging incident for a fraternity banned from campus in the 1980's.
Detroit residents interested in receiving help from PETA can send a hard copy of their most recent overdue water bill, as well as a pledge to go vegan for one month, to the organization's office in Virginia.
Their stories have sparked Congressional hearings, as well as pledges for institutional reform.
The Islamic State, also known as ISIS, releases a pledge video for only a minority of the attacks it claims.
