Automotive primer
Choose an undercoat by substrate, adhesion, corrosion protection and the requirements of the next paint layer.
A prepared foundation for the next layer
Primer describes undercoat materials that prepare a substrate for subsequent paint. A product may promote adhesion, provide corrosion resistance, help surface preparation, or combine roles. No single primer automatically performs all these jobs on every surface.
Primers are not limited to bare metal. Approved applications can include sound existing paint, factory electrocoat, filler or selected plastics, provided the exact product permits the substrate and preparation.
Primer, surfacer and primer-surfacer
Think first about function. An adhesion or corrosion-protection primer is not interchangeable with a material intended primarily to level minor surface imperfections. A primer-surfacer can combine functions, and some products support different modes with different specified mixes.
These names are not a list that must always be applied in sequence. Nor does a high-build product replace necessary panel straightening or filler work. Undercoat colour can affect coverage and colour development, but it does not replace the final colour layer.
Steel, aluminium, old paint and plastic
For exposed metal, check direct-to-metal approval and any required pretreatment or corrosion-protection layer. Steel and aluminium need not have the same requirements. For existing paint or electrocoated replacement panels, confirm that the coating is sound and follow its cleaning and abrasion conditions.
For plastic, identify the material and whether it is already painted. A specified adhesion promoter or additive may be necessary. Permission for one prepared plastic does not authorize every bumper. Covering corrosion, contamination or lifting paint does not fix the underlying problem.
Sanding and wet-on-wet processes
A sanding process allows the material to dry as specified before shaping or refining its surface. An approved wet-on-wet process permits the next layer after its stated flash-off without an intermediate overall sanding step. Wet-on-wet does not mean applying at any arbitrary time.
Check both the minimum wait and maximum recoat interval, as well as the specified hardener and conditions. Dust contamination or a missed window may require extra preparation. Do not substitute the schedule from another primer with a similar name.
Read the whole system before mixing
Identify the substrate and required function, then check the technical sheet for preparation, compatible hardener and reducer, film build, drying, sanding and overcoating. Review the safety information and the professional ventilation and protective equipment required for the operation.
The durability of the repair depends on the prepared substrate and compatible layer sequence, not simply on adding a primer. If the system or facilities are uncertain, resolve that before mixing or spraying.