Canal Lock Gate 

Conewago Canal

HISTORIC OVERVIEW

Conserved Canal Lock GateThe construction of Pennsylvania's Canal system began in 1797 with the Conewago Canal. It was primarily used as a means of transportation for people and materials. The long project provided jobs for many Pennsylvanians. It was hard work as they only had the use of picks, shovels, and wheel barrows, however after several decades the interlocking sections of canals grew to reach 1,243 miles throughout the state.

 

Heberling Associates, Inc. worked under a contract with Pennsylvania Department of Transportation to perform an extensive culture resources study of the Lewistown Narrows prior to the reconstruction of a 10 section off of route 22/322 along the Juniata River. During the investigative study near the Lewistown Narrows Canal Park, a portion of the remaining canal wall and cast iron lift lock gate was discovered.


PRE-TREATMENT CONDITION

Canal Lock Gate upon discoveryThe cast iron lock gate was bought to B.R. Howard & Associates Inc. to be examined and properly stabilized and preserved. The gate was found to be in an unstable condition having a heavy layer of iron corrosion and organic debris on the surface. The cast iron brackets which secured the gate to the to the canal had fractured. The upper bracket had lost both ends, leaving only the collar, in which the gate pivoted. A condition report along with proposed treatment was then generated for review prior to treatment.

 

TREATMENT

Mechanical removal of scalingB.R. Howard & Associates Inc. was given the approval to begin the project. The lock gate was submerged in a tank containing deionized water and soaked for several weeks. The water was drained and replaced every 3 days to reduce the chloride contamination. Initially the chlorides were recorded at over 200 parts per million, but was lowered to under 30 part per million over the course of a month.

 

After the chloride levels were significantly reduced, the gate lock was submerged in a new tank. This tank held a 5% solution of sodium hydroxide and was connected to a cathode of the rectifier that was adjusted to run a 15 amp current. Stainless steel was used as the sacrificial anode. This electrolytic reduction process was carried out for two weeks.

 

The gate lock was then again thoroughly rinsed in a tank of deionized water prior to the mechanical removal of the loosened corrosion product using metal picks and brushes. The surface scale was removed and the surface was vacuumed in preparation for the final stage of treatment.

 

A 2% tannic acid solution was heated and brush applied to the cast iron surface for 20 minutes, and allowed to dry for 24 hours. It was then hot waxed using a microcrystalline wax impregnated with carbon black pigments.

 


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