Difference Between Red Oxide and Zinc Chromate Primer

The key difference between red oxide and zinc chromate primer is that zinc chromate primer provides metals more corrosion resistance than red oxide.

Zinc chromate and red oxide are important chemicals that are often used in metal primers. These two substances differ from each other in their appearance as well as in their ability to provide corrosion resistance to metal surfaces.

CONTENTS

1. Overview and Key Difference
2. What is Red Oxide Primer
3. What is Zinc Chromate Primer
4. Side by Side Comparison – Red Oxide vs Zinc Chromate Primer in Tabular Form
5. Summary

What is Red Oxide Primer?

Red oxide is tetraoxide of lead. Other names for this chemical substance are red lead and minium. Red oxide does not occur in nature commonly, but we can use several simple methods to prepare it. This substance is important as a primer for metals, and as a component in paints that is useful in rust prevention.

Red oxide primer undergoes chemical reactions with iron surfaces and iron oxide, forming insoluble compounds known as plumbates. In plumbates, lead exists as a part of the anion. E.g. ferrous plumbate has the chemical formula Fe(PbO2), in which the cation is Fe²⁺. When applying red oxide on a steel surface, if traces of rust already exists on the steel surface, the primer will still adhere to this surface because the red oxide primer interacts with the surface via forming chemical bonds.

However, as per concerns regarding the lead poisoning, red oxide primer has fallen under the category of disuse. It’s also important to note that red oxide has uses in some glass formulations that show no significant health threat to the public.

What is Zinc Chromate Primer?

Zinc chromate primer is a coating chemical substance having the chemical formula ZnCrO4. It is important as an industrial painting and as a coating over iron or aluminum materials.  This substance was extensively used by the US military during the 1930s to painting aircraft for the prevention from corrosion. Moreover, this substance is useful in a variety of paint coatings for the aerospace and automotive industries.

Zinc chromate primer is important as a corrosion-resistant agent where it is applied to aluminum alloy parts first in commercial aircraft, and then in military aircraft. The major uses of zinc chromate are as an anti-corrosive and anti-rust primer. However, zinc chromate primer is highly toxic; it also destroys organic growth on the steel surface. Therefore, it is also used in spray paints, artists’ paints, pigments in varnishes, and making linoleum.

What is the Difference Between Red Oxide and Zinc Chromate Primer?

Red oxide and zinc chromate are useful as primers that are applied on metal surfaces before applying paint in order to prevent the metal surface from rusting. The key difference between red oxide and zinc chromate primer is that zinc chromate primer provides metals more corrosion resistance than red oxide. Moreover, red oxide appears in bright red colour while the zinc chromate primer appears in yellowish-green colour.

Below infographic summarizes the differences between red oxide and zinc chromate primer in tabular form.

Summary – Red Oxide vs Zinc Chromate Primer

Red oxide and zinc chromate are useful as primers that are applied on metal surfaces before applying paint in order to prevent the metal surface from rusting. The key difference between red oxide and zinc chromate primer is that zinc chromate primer provides metals more corrosion resistance than red oxide.

Reference:

1. Summers, V. (2019, March 02). What Is Red Oxide Paint? Retrieved November 06, 2020, Available here.

Image Courtesy:

1. “Minium-232908” By Rob Lavinsky, iRocks.com – (CC BY-SA 3.0) via Commons Wikimedia
2. “Zinc chromate primer” By 水水 – Own work (CC BY-SA 4.0) via Commons Wikimedia