Berntsen 2" diameter Bronze Survey Caps for Rebar
All Berntsen bronze survey caps for rebar are orbital formed from silicon bronze alloy 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 that 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.
Brass has been used in the manufacture of survey monuments and markers for many years. Iron pipe monuments with brass caps were used by federal government surveyors as early as the first part of the 20th century. Certain brass alloys, notably those with a high lead (a hazardous material) content, equal or greater than five (5) percent, are now viewed as archaic metals. Alloys that are typically used in survey monument components were Leaded Semi-Red Brass 81-7-9 (7 percent lead) and Leaded Red Brass 85-5-5 (5 percent lead). Few customers require these alloys for any reason other than tradition.
Berntsen’s Better Way
Berntsen pioneered the introduction of non-leaded brass alloys for survey monuments and markers in the mid-1980’s. Through our continued research and testing we have found that brass or bronze alloys containing high amounts of coppers, provide the best characteristics in corrosion resistance, strength and durability. We now exclusively use silicone bronze alloy (97 percent copper, 2 percent silicon) for our cold forged survey markers and caps. In an independently conducted test, Berntsen’s silicon bronze cap was found to have essentially no corrosion after 240 hours of salt spray per ASTM B-117-16.
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