Salesforce will soon be disabling TLS 1.0 support.
Starting in June 2016, Salesforce will begin disabling the TLS 1.0 encryption protocol in a phased approach across impacted Salesforce services. The disablement of TLS 1.0 will prevent it from being used to access the Salesforce service within inbound and outbound connections.
In Continuation to the great post on how to call salesforce APIs via BizTalk , the WCF behaviour can be extended to inforce any other TLS protocol.
ApplyClientBehaviour method can be modified to apply security protocol on the outgoing messages. By default this is SSL 1.0
You can pass on the parameter from the configuration like the other params.
WCF Behaviour extension would look something like.