2" diameter Aluminum Survey Caps for Rebar
All Berntsen aluminum survey caps for rebar are forged from 6000 series aluminum which is highly resistant to chipping, cracking and breaking. They feature the SureGripT plastic insulator that locks the cap tight on to the rebar or pipe and helps prevent dissimilar metal corrosion. They feature a deep hex socket that won't "wobble" when tapped on to the rebar.
A good survey cap for rebar or pipe must virtually eliminate dissimilar metal corrosion. What typically happens is the survey cap loosens over a short period of time. This confirms metallurgical theory. Aluminum is less "noble" than steel and an electrical current will actually flow from the aluminum (+) to the steel (-). Corrosion will occur in the anode (+) area of the battery like combination of metals in the presence of moisture (air or soil acting like an electrolyte).
Berntsen originated the SureGripT insulator/wedge which effectively isolates the survey cap from the steel and de-forms around the ribs of the rebar. The hex shape fills with the deformed plastic material and the survey cap is locked on with a super tight compression fit. Great force is required to remove the cap.
Our aluminum material is versatile and resistant to most environment conditions, however, if the survey markers are intended to be used in high traffic or caustic environments, such as roadways or salty conditions, we highly recommend using bronze survey markers to improve the lifetime of the markers.
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In high purity form, aluminum is a soft and ductile metal. Aluminum of 99 percent or higher purity has many applications but has very low structural strength. Most commercial applications for aluminum require greater strength than can be achieved with high purity aluminum. Additional strength is achieved in aluminum by adding other elements to produce alloys. These elements, either alone, or in combination impart strength to the metal. Additional strengthening is also possible by means of heat treating techniques or other processes such as cold forging. (Cold forging provides only a moderate increase in strengthening high purity 1000 Series aluminum; 1000 Series aluminum is not heat-treatable). Commercially pure aluminum components can also function like anodes used to protect buried pipelines and sacrifice themselves to protect the (iron or steel) pipe.
Berntsen's Better Way
6000 Series Aluminum-Berntsen has always worked with strong corrosion resistant alloys. Alloys in this group contain magnesium and silicon (which form magnesium silicide) and make the alloy heat-treatable. Alloys in this series can also gain considerable strength through cold working techniques such as orbital cold forming, a Berntsen exclusive in survey monument components since 1986. Several components of Berntsen survey monuments and markers such as caps, pipe and rods are manufactured from this versatile alloy series, and, depending on the intended use, may be heat-treated for added strength.