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struction, usually being a single casting, with no attached parts, sights, handles, or bolts that can create crevices that trap moisture. Being a single piece, effective, full coverage painting is very feasible. This is impossible on a modern, multi-part piece that has been welded into a single lump with perhaps hundreds of crevices to corrode. Acid rain, salt spray or worse, usually both, penetrates
into these crevices to attack the bare metal within. The occasional paint job these corroding military pieces receive is often exacerbating the effect of the crevice corrosion. Every decade or so, someone notices the rust and decides to do something about it. This usually takes the form of a hasty paint job. Since it is impossible to sand the corrosion away inside the welded pieces, the rust is
simply painted over and soon returns. Often the corrosion is much worse than if the piece
had been left unpainted.
Corrosion vs. display locations
The twentieth century steel pieces are in rapid decline everywhere. We have inspected all pieces in the Kingston area, as well as outdoor pieces in Ottawa and London Ontario; Halifax, Nova Scotia; Shilo, Manitoba; and Fort Drum, NY. Everywhere we look these military pieces are failing from a devastating attack by rampant corrosion. What our enemies could never do, corrosion is achieving silently, right under our collective noses. This is for several principal reasons. Invariably, military monuments are placed close to roadsides. In Canada and the northern parts of the United States, this can be considered a marine splash zone, a very corrosive environment indeed. Throughout our long winter, the Department of Highways spread chlorides to thaw ice, which the passing traffic quickly turns into a salty mist or aerosol that is blown over nearby structures and monuments. These high levels of chlorides with the ever present slush and snow easily slip between the cannons' parts to become a powerful catalyst for corrosion.
The steel battle tanks and guns on permanent display in front of the National War Museum on busy Sussex Drive in Ottawa have, for example, seriously deteriorated. These pieces now have lost all of their accessories to corrosion. Steel artillery and armored vehicles on outdoor display at the Royal Canadian Regiment Museum in London, Ontario, and at the museum of the Royal Canadian Artillery in Shilo, Manitoba, show all of these same forms of corrosion. So do the WWII military pieces at the Royal Artillery Park in Halifax, Nova Scotia. However, the cast iron cannons of the nearby Halifax Citadel are in excellent condition even though they are a full century older.
FORMS OF CORROSION
Massive corrosion
Crevice corrosion
Galvanic corrosion
The following examples illustrate the various forms of corrosion that have been observed on military pieces exposed boldly to atmospheric environments. In the present context, the term "massive corrosion" is used instead of the traditional term "uniform corrosion" to describe a state of corrosion so advanced that falling chunks of rust are a sure sign of the abandonment sometimes incurred by military artifacts.
For example Figure 1 shows how the steel wheel component of a 25 Pound
Howitzer exposed in Artillery Park beside a busy street in front of Halifax Citadel
(Figure 2), is falling apart in big chunks of rust. Crevice corrosion is most devastating to these monuments. Impossible to repair, or properly protect with paint coatings, it is destroying them all. As the corrosion creeps out of the crevices or from an incomplete weld joint the paint is lifted by the corrosion to form blisters that eventually break with streaks of rust.
(Figure 3). Unbroken blisters are a swelling of the paint caused by the corrosion expansion. The same corrosion environment can be so severe to produce the "pillowing" that has lifted up the plaque shown.
(Figure 4). While primarily steel, most of the modern era pieces have some dissimilar metal components attached to them, such as aluminum sight cones and rivets, and chrome plating of muzzles and handles for decorative purposes. All of these create an opportunity for galvanic corrosion to occur.
(Figure 5). And with the electrolyte effect of acid rain or salt in marine zone mists, galvanic corrosion rapidly proceeds. To add to these difficulties, commemorative plaques are added with no consideration for the galvanic mismatch, producing defacing damage in the first years of exposure. (Figures 6 to 8).
CONSERVATION vs. INHIBITION
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