Expert Care for the Alamo’s Battle Cannon

Two Alamo cannon before conservation treatment.

Over a period of more than fifty years, the Alamo’s surviving 18th century cannon had been set into concrete bases and left without substantive preservation treatment. This had led to corrosion in the bore and along the underside of the cannon, where moisture was permitted to cause deterioration. In 2017, the Alamo Trust began a major project to rectify this situation and contracted with Texas A&M Conservation and Research Lab to conserve these guns.

A Step-by-step Process

Two Alamo cannon soaking in a special chemical bath.

First, each cast iron cannon is documented and mechanically cleaned. Each then goes through an electrolytic reduction (ER) process to remove any painted surfaces, corrosion products and any chloride ions.

An Alamo cannon emerges from a rinse bath.
Credit: Texas General Land Office

During the second stage in conservation, the cannon are rinsed in a series of boiling reverse-osmosis (R/O) water baths, to remove any residual chemicals in the metal.

A newly conserved Alamo cannon on display.

After rinsing, the cannons are coated with tannic acid to create a layer of ferric tannate, which makes the iron more corrosion resistant. Then the surface is sealed with a matt polyurethane sealant, to form a water and oxygen resistant barrier to the conserved cannon. After that, each cannon is then ready to be put back on display.