From As-Cast to Plated: Picking the Finish
As-cast and mechanical finishes
Many internal or non-visible parts ship as-cast with only machining on critical faces. Shot blasting or tumbling gives a uniform matte texture that hides flow marks — an inexpensive upgrade for visible structural parts.
Remember machining exposes fresh alloy: mask or re-plan finishing where machined surfaces must match cast ones.
Paint systems: powder vs e-coat
Powder coating gives durable, film-build finishes in many colours — the default for visible housings. E-coat (electrodeposition) excels as a thin, uniform corrosion base layer, often paired with powder as a two-coat system for outdoor exposure.
Pre-treatment (conversion coating) is where most coating failures actually start; specify it explicitly.
Plating and special cases
Zinc die castings plate well and are the classic basis for bright chrome hardware. Aluminum needs zincating before plating, adding cost. For EMI shielding, conductive coatings or casting-in inserts can be specified instead of full plating.
FAQ
Which finish for outdoor exposure?
E-coat base plus powder topcoat is a common corrosion package for exterior aluminum die castings.
Can zinc parts be chrome plated?
Yes — zinc die castings are the traditional substrate for decorative chrome on hardware and trim.
Why does powder coat peel at edges?
Usually insufficient pre-treatment or edge geometry; sharp cast edges thin the film — add radii and specify conversion coating.
Is as-cast surface good enough?
For internal and hidden parts, often yes; specify cosmetic requirements only where the part is visible to keep cost down.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.