Organic Coatings on Aluminum Surfaces

Another name for this chemical substance is Phosphorous acid.

In the aviation and automotive industries, chromate-based coatings were used on aluminum surfaces to prevent corrosion. However, environmental responsibilities and high-performance demands in this field have necessitated new research.

Therefore, environmentally friendly coating chemicals based on organic and organic-inorganic phosphonic acids will replace products that are toxic and have low performance.

In the following sections, we will share details about different types of compounds derived from phosphonic acid on aluminum and aluminum alloy materials.

How Does Aluminum Resist Corrosion?

There are several reasons for using aluminum in engineering applications. These include low cost, a high strength-to-weight ratio, and formability. Its use in the automotive, aviation, and construction industries is of great importance. Additionally, its corrosion resistance is extremely important.

In fact, due to its nature, aluminum easily oxidizes to form a passive, protective oxide layer.

What Are the Advantages of Organic-Inorganic Hybrid Coatings?

The application methods for these types of coating materials are simple. The main advantages of hybrid materials are that their organic layers provide good corrosion resistance and mechanical performance with positive characteristics.

Many phosphonic acids are excellent chelating agents due to their protective effect against corrosion on metal surfaces and metal oxides, nano-particle stabilization, hydrophobization, hydrophilization effect, and tendency to adhere to organic layers.

Thanks to these properties, they form hydrolytically stable bonds with metals.

How Do Phosphonic Acid-Based Substances Work?

Phosphonic Acid polymerizes with a hydrophobic group or acts as a binder between chemically stable protective materials. These molecules are applied to the aluminum surface by dipping, spraying, or are incorporated into the polymeric matrix coated on the metal surfaces in a subsequent process. One of the new methods is deposition on the surface, supported by an ultrasonic method.

Phosphonic acids with hydrophobic aliphatic groups and fluorinated groups increase the hydrophobicity of the metal surface. This creates a barrier against aqueous solutions, thus having an inhibitory effect on corrosion formation.

The acidic phosphorus compound is dissolved in a suitable solvent, and a portion of the resulting solution is added to a previously prepared copolymer solution. The ratio of the acidic phosphorus to be used in this application is very important. If it is below the optimum amount, it will not yield the desired result. If added above the limit, it will not solidify on the aluminum surface and will remain in a fluid or sticky form.

Some Phosphonic Acid Derivatives Used Are as Follows:

• PhenylphosphonicAcid(PPA)
• VinylphosphonicAcid(VPA)
• 1,12-DodecyldiphosphonicAcid(DDP)
• Amino Trimethylene Phosphonic Acid (ATMP)
• Ethylenediamine Tetra Methylene Phosphonic Acid (EDTPO)
• 1,2-Diaminoethanetetrakis-Methylenephosphonic Acid (DETAPO)
• (12-Ethylamino-Dodecyl)-Phosphonic Acid
• Aminopropyl Phosphonate (APP)
• ω-(3-Phenylpyrrol-1-ylalkyl) Phosphonic Acid (Cn-Ph-P)
• ω-(2,5-Dithienylpyrrol-1-yl-alkyl) Phosphonic Acid (SNS-n-P)
• (1H,1H, 2H,2H-Heptadecafluorodec-1-yl) Phosphonic Acid (HDF-PA)
• Poly (Vinyl Phosphonic Acid) (PvPA)

What Other Chemicals Are Used for Coating on Aluminum Surfaces?

Toluene diisocyanate (TDI 80/20), methyl methacrylate, ethyl methacrylate, butyl methacrylate, Triethylamine, Titanium dioxide, iron oxide, Silicone oil, Polydimethylsiloxane, Sodium dodecyl sulfate