Question

Which of the following compounds can be used as an inhibitor in moulding materials for avoiding chemical reaction with magnesium alloys?

(a) Sodium silicate

(b) Water

(c) Hydrogen silicate

(d) Potassium borofluoride

I had been asked this question in a job interview.

Question is taken from Magnesium Alloys in section Foundry Introduction & Materials of Casting-Forming-Welding II

Answer 1

Correct answer is (d) Potassium borofluoride

To explain I would say: Moulding materials are effectively inhibited by adding 1 to 2 percent of potassium borofluoride. And controlling of inhibitor content in moulding materials is very important because they can affect setting times. Sometimes elimination of silica content from moulding materials also takes place to avoid chemical reactions.