Enamelware usually refers to Vitreous enamel also called porcelain enamel which is a material made by fusing powdered glass to a substrate firing usually between 750 and 850 °C (1,380 and 1,560 °F).
The powder melts, flows, and then hardens to a smooth, durable vitreous coating which can be applied in a number of coats.
Quality of Enamelware is dependant on the gauge of steel and number of coats applied to the product.
Powder Coating is a type of coating that is applied as a free-flowing dry powder which is mainly used for coating of metals and Tinware.
The coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a "skin".
The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint.
These are common features of Enamel Production they are not defective spots but Normal Signs of Manufacturing.