Hi @Maximilien, welcome to the community!
Credentials are only loaded once, no matter how many items you’re passing on to the node. So if you want to use different credentials for each item, my suggestion would be to split up your data in batches (with a size of 1 item per batch) using the Split In Batches node.
A generic workflow demonstrating the idea would be this one:
The credentials contain an expression of {{$json["address"]}}, reading the address field:
When running the workflow you can see that each request uses different credentials and sends them to my webhook.site URL:
Hope this helps!