Thicker is not automatically better, and one finish does not suit every spring. Substrate strength, wire size, fit and environment constrain the process choice.
Define the purpose first
Rust prevention, appearance, conductivity, friction and solderability are different goals. Drawings should specify function rather than color alone.
Consider thickness and coverage
Coatings change wire and fit dimensions, while coverage can vary at coil contacts, hook interiors and complex bends. Inspect critical dimensions after finishing.
Review embrittlement for high-strength steel
Acid cleaning and electroplating can introduce hydrogen-embrittlement risk in high-strength steel. Review strength, pretreatment, baking and validation together.
Stainless still needs a clean surface
Cleaning and passivation support cleanliness and restoration of a corrosion-resistant surface. They cannot repair deep damage, inclusions or an incorrect alloy.
References
This article is informed by public standards catalogues and industry engineering resources. Project values should be confirmed by drawings, material certificates and sample validation.