Simple Analysis on the Snowflake Corrosion of Oxidized Aluminum Profiles

Edit: Wuxi XSX Metal Materials Co.,Ltd    Date:Jul 12, 2016

Generally, there is a natural oxide film and other contaminants on the surface of original aluminum material which are quite likely to cause corrosion. And in the solution of acidic, basic and neutral, aluminum profile is prone to corrosion, which will destruct its surface properties, shorten the lifespan and limite the application areas.

The corrosion ways of aluminum and aluminum alloy are the followings:

> In the atmosphere, the seawater and netural aqueous solution can cause "spot corrosion"

> With other metals, potential differences can cause "galvanic corrrosion"

> Combined with aluminum or other metals, there is a tiny surface contact gap in between, which can cause "crevice corrosion"

For aluminum industrial profile manufacturers, in pratical aluminum profile surface treatment process, the aluminum metal will react with the solution and appear "snowflake corrosion" sometimes.

According to relative research, the main reasons of snowflake corrosion appears are as below:

1. Chemical composition-The higher content of Zn is in metal materials, the severer the snowflake corrosion will grow; And Gallium is also another critical element that will effect.

2. The bathing time control in the trough-The first step of chemical surface treatment is in the oil removing tank. And then comes to rinse. The bathing time in the rinsing bath is crucial to the profile surface quality. The longer the bathing time is, the severer the snowflake corrosion will be.

3. Neutralized nitric acid- After the alkali etching, the neutralization is processed to ahieve agleam surface. The traditional technology of removing surface dust is to use nitric acid. Aluminum material surface will form a very thin oxidation film in nitric acid solution which plays an inactive protection role. However, excess content of nitric acid will speed up the etching and cause punctiform corrosion.

4. Rinsing bath after neutralization- There are sulphuric acid and nitric acid in the neutralization bath. During the reacting, more acidic materials will come up, causing the decreasing of PH value in solution and snowflake corrosion emerges.

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