Surface Treatments — Name the Oxidising Process for Aluminium and Magnesium Which process is specifically used to produce a controlled oxide layer on aluminium and magnesium components?

Introduction / Context:
Surface engineering tailors corrosion resistance, wear behavior, and aesthetics. Aluminium and magnesium rely on their oxide films for protection, and certain processes intentionally thicken and stabilise these films.

Given Data / Assumptions:

• Work material: aluminium or magnesium alloys.
• Goal: build a protective oxide layer with controllable thickness and porosity.
• Electrolytic processes are permitted.

Concept / Approach:
Anodising is an electrolytic oxidation process in which the component acts as the anode. The oxide layer formed (alumina on Al, magnesia on Mg) is thicker, harder, and more adherent than the native oxide, with pores that can be sealed or dye-filled for color and improved corrosion resistance.

Step-by-Step Solution:
Identify the target substrate: Al/Mg families.Match the objective: grow a controlled oxide film via electrochemistry.Recognise anodising as the correct process.Eliminate unrelated diffusion/coating processes (galvanising/sheradising) and conversion coatings for steels (parkerising/phosphating).

Verification / Alternative check:
Common industrial practice: architectural aluminium and consumer electronics enclosures use anodised finishes.

Why Other Options Are Wrong:
Galvanising/sheradising: zinc coatings, not oxide growth on Al/Mg.Parkerising/phosphating: phosphate coatings mainly for steels.

Common Pitfalls:
Assuming any conversion coating suits Al/Mg; anodising is the canonical choice.

Final Answer:
anodising