Scope creep - Extra scope is added to the project without considering the impact of change on time, cost, quality, risks etc.
Gold Plating - The team provides extras over and above the scope baseline. Scope Baseline remains “unchanged”.
The key differences are:
With scope creep, the scope baseline is changed, but with gold plating, the scope baseline remains the same.
Scope creep usually results from the customer or other stakeholders requesting for a scope expansion, but in case of Gold Plating, project team voluntarily provides extras without the customer requesting for them.
Both Scope Creep and Gold Plating are bad for the project and should be avoided.