Tech Scrap information in The Surge is on this page.
In The Surge, Tech Scrap serves as character's XP. You can use it to boost your stats, or upgrade weapons or gear.
If you haven't installed the new update, you can get unlimited scrap by selecting your highest mk piece of armor, unequipting it, then holding the destroy and pressing the equip button at the same time, this will net you the amount of scrap destroying that armor would give without destroying it. You can repeat this process infinitely.