It is not applied when the effect of an already face-up Spell or Trap Card is activated or when the effect of a Spell or Trap Card in the Graveyard is activated. (It applies if a Spell or Trap Card is activated.)
It is not applied unless "Scrap Shark" was face-up at the time the card or Effect Monster’s effect was activated.
Even if a card or monster effect is activated during the Damage Step before damage calculation while "Scrap Shark" is battling, it is not destroyed until after damage calculation and is considered to be destroyed by its own effect even if it loses the battle.
The effect to send a “Scrap” monster to your Graveyard also activates during the Damage Step.