Invincible after collision

Hi,

I'm making a physics game where if you hit something with great enough velocity you take damage. What I'm trying to do here is to add invincible time after on collision. I have a coroutine with a float time that makes invincible true after on collision. I thought this would work and been searching everywhere but can't find answers.

Thanks for any help.

public int attackDamageLow = 10; public int attackDamageMid = 20; public int attackDamageHigh = 30; public float hitDelay =5f; private bool Invincible = false;

 GameObject player;
 Health playerHealth;
 //EnemyHealth enemyHealth;
 bool playerInRange;
 float timer;

 // Use this for initialization
 void Awake () 
 {
     player = GameObject.FindGameObjectWithTag ("MainPlayer");
     playerHealth = player.GetComponent<Health> ();
     //enemyHealth = GetComponent<EnemyHealth> ();
 }

 void OnCollisionEnter (Collision other)
 {
     if (!Invincible) {

         if (other.gameObject == player) {
             float mag = other.relativeVelocity.magnitude;
             if (mag > 40f) {
                 
                 AttackHigh ();
                 Debug.Log ("S");
                 StartCoroutine (Delay ());
             } else if (mag > 20f) {
                 
                 AttackMid ();
                 Debug.Log ("M");
                 StartCoroutine (Delay ());
             }

             else if (mag > 10f) {
                 
                 AttackLow ();
                 Debug.Log ("H");
                 StartCoroutine (Delay ());
             }
     



             }
     }

     }







 void AttackLow ()
 {
     //timer = 0f;

     if(playerHealth.currenthealth >0)
     {
         playerHealth.takeDamage (attackDamageLow);

     }
 }

 void AttackMid ()
 {
     //timer = 0f;

     if(playerHealth.currenthealth >0)
     {
         playerHealth.takeDamage (attackDamageMid);

     }
 }

 void AttackHigh ()
 {
     //timer = 0f;

     if(playerHealth.currenthealth >0)
     {
         playerHealth.takeDamage (attackDamageHigh);

     }
 }

 IEnumerator Delay()
 {
     Invincible = true;
     Debug.Log ("True");
     yield return new WaitForSeconds (hitDelay);
     Debug.Log ("false");
     Invincible = false;
 }

}