Formating default data for text fields

Here's my setup: In migration file:

... t.column :perm0, :int, :default => User::Perms::Base, :null => false ...

(User::Perms:Base = 1)

In app/views/login/add_user.rhtml: ... <label for="user_perm0">Permissions:</label> <%= form.text_field :perm0, :size => 10 %> ...

While (quite magically), provides me with a form with the default value "1" helpfully prefillled.

The fly in the ointment is that, should I decide on a more interesting default, I'm going to want the value displayed zero-filled in hex (%08x instead of %d). Any ideas?