Which type of primer is specifically designed to convert surface rust?

The correct choice is self-etching primers because they contain chemicals that can chemically bond with rusted surfaces, converting rust into a more stable compound. This type of primer allows for better adhesion of the subsequent paint layers and is particularly useful when painting over metal surfaces that may have some corrosion. Self-etching primers are commonly used in automotive refinishing as they effectively prepare the surface for a topcoat by ensuring durability and preventing rust from reappearing.

The other options do not perform the same function. Oil-based primers are typically used for their excellent adhesion and sealing properties but do not specifically address rust conversion. High solids primers are designed for better build and coverage but also lack rust conversion capabilities. Latex primers, while versatile for various surfaces, are not suitable for dealing with rust on metal surfaces, as they are not formulated to handle the chemical changes associated with rust.