OK - Then like I suggested on the other site - I would just buy a tin of primer for steel from the shop.
I, and others there, asked what the application was - is it indoor? Warm place? Outdoor, Exposed area, sea side? Read the tins - if you need a strong rust prevention then get a high zinc, zinc phosphate or aluminium tripolyphosphate loaded primer - all the info you need will be on the tin.
Where is the substrate? External/internal, sheltered/exposed?