Expeditions to the Monitor have yielded an amazing variety of artifacts: huge iron components, delicate glass bottles, lumps of coal, wood paneling, a leather book cover, walnut halves. In 2001 alone, more than 250 artifacts arrived at The Mariners' Museum to be conserved and prepared for exhibition at The Monitor Center.

Each artifact presents a different challenge to conservators as they seek to reverse the damage done by nearly 140 years of immersion in saltwater. Once-mighty iron components such as the engine and propeller have been rendered so fragile that they will disintegrate without years of painstaking treatment. Delicate glass bottles can often be cleaned and readied for exhibition in just a few days or weeks. Layers of iron must be dissolved off of coal pieces; walnuts must be chemically dried; both iron and brass are treated by electrolytic reduction.


Fragile as iron: A conservation challenge.
Courtesy of the Daily Press

Conserving the iron artifacts recovered from the Monitor is a race against time. Once recovered from the ocean, the ship's fragile, salt-contaminated iron can split apart if exposed too long to the air. After recovery, the artifacts are kept wet and quickly transported to The Mariners' Museum, where they begin intensive treatment to counteract the effects of being submerged in seawater for nearly 140 years.


The corrosion process

In a reduced-oxygen environment such as the sea bottom, iron becomes mineralized. Its new state contains salts, which form crystals within the material when it dries. This reaction can cause the material to tear apart, much like frost-heaving in frozen soil.

Conserving iron pieces recovered from the sea involves reduction of the object to arrest corrosion, stabilization of the material, and removal of the salt. The length of time for the process depends on the rate at which salt can be removed from the mineralized iron. Large items with thicker corrosion layers, such as the engine or propeller, require more time than do smaller ones.

The fragile, salt-contaminated iron artifacts recovered from the Monitor present the greatest challenge to conservators. More than 65 tons of iron items have been raised from the wreck and will require years of treatment before the deteriorated metal is stable.

Layers of decay
Submerged iron oxidizes into various corrosion compounds that form in unstable layers. It also becomes covered with surface encrustations, as well as destabilizing chlorides from sea water.

Surface encrustations
A combination of sand, sediment, marine life, and iron oxides that bonds to the surface.

Iron oxides (rust)
Progressive oxidation will disintegrate iron over time.

Electrolytic Reduction
Uses low-voltage electrical current and an alkaline bath to reverse the effects of sea water on submerged iron.

Slow going

Large iron artifacts can require years of conservation. Multi-part objects such as the Monitor's steam engine and turret must be disassembled to insure thorough treatment.

Electrolytic Reduction

The Monitor turret and other metal artifacts are being conserved through a process known as electrolytic reduction. This procedure helps remove organic encrustations from the surface and corrosive chloride compounds from the interior. Without conservation, these objects would corrode and disintegrate.

The metal objects are submersed in an electrolytic solution of sodium carbonate or sodium hydroxide. Platinum surface electrodes are then suspended around the metal artifacts and a 3- to 3.5-volt current is passed through the objects. This removes chlorides from the artifacts and stabilizes them through the process of reduction. This process also loosens the marine encrustation consisting of seabed debris cemented by corrosion products. The chlorides are trapped in the electrolyte solution, which is changed when it becomes contaminated with chlorides. The process is complete when no more chlorides can be detected in the solution.

What are the white tubes?
In order to complete the electrolytic reduction circuit in the conservation tank, there has to be a place for the electricity to go when it leaves the artifacts. Platinum coated electrodes complete the circuit. The white tubes cover and protect the electrodes.

Why are there bubbles?
When the electric current flows out of the artifacts into the solution in the tank, it causes water molecules to break down into their component parts. This creates bubbles of hydrogen and oxygen.

How long does the process take?
It is estimated that it will take fifteen to twenty years to reduce the corrosion and to remove all the salt from the turret. Other objects, such as the engine, may take up to ten years.

Why is this treatment necessary? Most materials made or refined by humans become altered by minerals and salt in the chemically and biologically active medium of sea water. If left untreated after recovery, these artifacts would rapidly corrode and disintegrate. Unprotected wrought iron loses an average of approximately 0.001 meters per year to corrosion in sea water. Since the Monitor sank in 1862, an iron plate that once was a half-inch thick has been reduced to only millimeters. What happens when the objects are removed from the tanks? When the reduction and chloride removal phases of iron conservation have been completed, the artifacts are removed from the tanks. Their surfaces are stabilized with phosphates and tannates and then coated with wax, lacquer, or paint to protect them from moisture and other damaging substances. The fragile, salt-contaminated iron artifacts recovered from the Monitor present the greatest challenge to conservators. More than 65 tons of iron items have been raised from the wreck and will require years of treatment before the deteriorated metal is stable.		Layers of decay on a section of iron exposed to saltwater for decades.

Layers of decay
Submerged iron oxidizes into various corrosion compounds that form in unstable layers. It also becomes covered with surface encrustations, as well as destabilizing chlorides from sea water.

Surface encrustations
A combination of sand, sediment, marine life, and iron oxides that bonds to the surface.

Iron oxides (rust)
Progressive oxidation will disintegrate iron over time.

Chloride
Absorbed from the ocean, they destabilize iron and accelerate corrosion. They also crystallize when they dry and can break an iron object apart from the inside out.