21. Galvanising (i.e., zinc coating) of steel sheets is done to Prevent its rusting by contact with corrosive atmosphere Protect the base metal by cathodic protection Both A & B Neither A nor B ✅ The correct answer is option C.
22. Steel balls for ball bearings are generally made of __________ steel. Cast Stainless Free carbon Carbon chrome ✅ The correct answer is option D.
23. Which of the following will have the highest melting point? Pig iron Mild steel Wrought iron High carbon steel ✅ The correct answer is option C.
24. __________ moulding process can not be used for thermoplastic plastics. Compression Extrusion Injection None of these ✅ The correct answer is option C.
25. Nickel is a __________ material. Ferromagnetic Diamagnetic Paramagnetic None of these ✅ The correct answer is option A.
26. Cast iron vessels are not suitable for the storage of Freon H₂SO₄ (95%) at room temperature H₂SO₄ (fuming) Wet SO₂ ✅ The correct answer is option D.
27. Cast iron is a __________ material. Brittle Ductile Tough Malleable ✅ The correct answer is option A.
28. The heat treatment process to which castings and the steel balls produced by cold heading are subjected is Tempering Normalising Annealing None of these ✅ The correct answer is option B.
29. How many atoms are there per unit cell in a body centred cubic lattice system? 2 3 4 6 ✅ The correct answer is option A.
30. Phenol is not shipped in Nickel lined steel tank cars Galvanised or tin lined drums Boxed glass carboys Cast iron containers ✅ The correct answer is option D.