In aluminum plate processing applications, pickling and passivation is a critical process. While aluminum plate inherently possesses a certain degree of corrosion resistance, this process, focused on optimizing performance, extending lifespan, and ensuring safety, focuses on resolving surface defects, building a protective barrier, and adapting to diverse scenarios.

1. The "Inherent Defects" of Untreated Aluminum Plate: The Root of the Necessity of Pickling and Passivation

During rolling, cutting, and storage, aluminum plate surfaces are susceptible to two types of surface hazards

First, oxidation and residual contaminants. Aluminum easily forms a 2-3nm uneven natural oxide film, which is ineffective against water, oil, and other contaminants. Residual oil from processing can cause localized corrosion, and contact with other metals can easily trigger electrochemical corrosion, resulting in black marks or white spots.

Second, processing damage and microscopic defects. Plastic processing can produce scratches and expose grain boundaries, and residual oxide scale may remain after heat treatment, affecting both appearance and reducing adhesion in subsequent processing steps. These defects can affect appearance at best, shorten lifespan, and even cause safety issues, such as metal ion migration in food-contact aluminum sheets and corrosion and peeling of architectural aluminum sheets.

II. The "Dual Role" of Pickling and Passivation: A Synergistic Effect of Cleaning and Protection

Pickling and passivation are a combined process of "pickling and decontamination" and "passivation film formation":

(I) Pickling: "Deep Cleaning" to Remove Surface Hidden Dangers

Using mixed acids such as nitric acid and hydrofluoric acid, it achieves three main goals:

Dissolves oxide layers and rust, revealing a fresh metal substrate;

Emulsifies and decomposes oil stains, removing impurities such as dust and debris;

Minor corrosion smoothes out minor scratches and optimizes surface smoothness. (II) Passivation: "Building a Shield" to Improve Corrosion Resistance

A dense 5-15nm aluminum oxide passivation film is formed through chemical or electrochemical methods to:

Isolate corrosive media such as water, oxygen, and salt spray;

Improve chemical inertness, making it suitable for harsh environments such as marine and chemical industries;

Extend the lifespan by 3-5 times, for example, extending the lifespan of architectural aluminum panels from 5-8 years to over 15 years.

III. The "Application Value" of Pickling and Passivation: A Key Guarantee for Adaptation to Diverse Scenarios

Architectural Decoration: Provides uniform surface gloss and weather resistance, improving adhesion to paints;

Food and Pharmaceutical: Removes oil and impurities, with the passivation film complying with GB 4806.3-2016;

Aerospace: Eliminates stress corrosion and improves fatigue resistance at high altitudes;

Electronic and Electrical: The passivation film provides insulation and reduces the risk of electrical leakage in equipment.

Aluminum plate pickling and passivation is a key process that combines "cleaning and protection" to safeguard the performance and lifespan of aluminum plates and support operations in multiple industries. In the future, the process will be upgraded to be more environmentally friendly and automated (such as chromium-free passivation), expanding the application space of aluminum plates.