You can send bitcoin to any Bitcoin wallet for free with Bitstack.
To send bitcoin using the blockchain:
Navigate to the Wallet tab in your app
Tap on the Airplane button
Enter the amount of bitcoin you want to send
Scan a Bitcoin address QR code or enter a BTC address
Tap Confirm
Note:
You cannot yet receive bitcoin from any wallet using the blockchain (this feature will be available soon).
The minimum amount per transaction is 0.00006000 BTC or 6,000 sats (Satoshis).