Coating a specific length of a rebar with epoxy and leaving the remaining length black.
Coating a specific length of a rebar with epoxy and leaving the remaining length black.
(OP)
I'm sorry for this stupid question.
Case: The column dowels must be epoxy-coated and extend above the ground level with 1m, then black steel can be used.
The common practice is to make the lap splice between the coated dowels and long. black steel above that limit, which for a reason it's not possible.
Q. Is it possible to coat a steel rebar to a specific length with epoxy and the remaining part kept black ? what about the bond at the section between coated and uncoated parts?
Please I need an quick answer through the specs.
Case: The column dowels must be epoxy-coated and extend above the ground level with 1m, then black steel can be used.
The common practice is to make the lap splice between the coated dowels and long. black steel above that limit, which for a reason it's not possible.
Q. Is it possible to coat a steel rebar to a specific length with epoxy and the remaining part kept black ? what about the bond at the section between coated and uncoated parts?
Please I need an quick answer through the specs.






RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
Dik
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
Dik
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
Is there any specs, research or text book ensure our opinion ?
dik & Ron. Do you have any specs, research or text book for that ?
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
Dik
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
(Note...Brown finds only a 5 yr. service life increase with using ECR...not much in the scheme of things, relative to cost and effort)
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
Dik
RE: Coating a specific length of a rebar with epoxy and leaving the remaining length black.
Second, connecting coated and uncoated bars results in a macrocell corrosion potential. This is where small holes in the coating result in significant local corrosion because the relatively large uncoated bar acts as an anode, sinking free electrons which would be "trapped" within the coating of an isolated, fully-coated bar. Corrosion is an electrical process, and the coating acts as a barrier to flow of electrons.
Do not partially galvanize anything. This will result in the partial zinc coating acting to protect both the coated and uncoated bar, leading to premature oxidation of the zinc, resulting is loss of protection.
Epoxy-coated bar is not really very expensive, particularly since you are not talking about a large quantity.
As to the epoxy bashing, there are 100,000 bridge decks in the US using epoxy-coated bar. Of these, fewer than 200 have experienced premature deterioration. The product is used every day in every state, because it represents the best value for tax dollars under most circumstances. Where the exposure is severe or construction is expected take its toll on the coating, stainless is frequently used. Galvanized bar is also very good in most applications requiring corrosion resistance, but provides limited protection in some conditions (the zinc coating is sacrificial so the life is limited by that.) The first line of defense against corrosion is proper cover and concrete quality. Make sure there is proper consolidation and shrinkage is minimized to avoid excess cracking.
The problems in Florida and Hawaii were related to handling problems, and macrocell corrosion where black steel was mixed with epoxy. Both of these are addressed in the relevant design and construction standards, some of which were changed when macrocell corrosion was identified after these events. Handling is addressed in industry publications and the ASTM A775 spec. The coating is tough, but if they tear up the coating during construction, it certainly can't be expected to work properly. FHWA has long term projects which are showing good performance of galvanized, epoxy, and stainless bars under very harsh conditions. We expect publication of these findings very soon.