(a) Attachment. A security interest attaches to collateral when it becomes enforceable against the debtor with respect to the collateral, unless an agreement expressly postpones the time of attachment.
(b) Enforceability. Except as otherwise provided in subsections (c) through (i), inclusive, of this section, a security interest is enforceable against the debtor and third parties with respect to the collateral only if:
(1) Value has been given;