Aluminum in contact with concrete 1

[khoward]

We have several aluminum slide gate frames in a municpal wastewater treatment facility that appear to be oxidizing and spalling the concrete channels.
My question is there any way to passivate the aluminum guides that are cast into the concrete to stop the spalling of concrete or do we have to remove the guides? Is it possible to grout the guides in and prevent further oxygen from getting to the aluminum and stop it's oxidation. We suspect the guides were not coated prior to installation into the concrete.

we are scheduling replacment of the aluminum guides and gates with FRP surface mounted units at this time.

 

[FSS]

If the aluminum is in direct contact with the concrete then you definitely have a problem. Aluminum needs to be isolated in order to prevent the types of problems you are describing. Bituminous or similar coatings which provide a barrier can be used. An epoxy type grout (different chemical composition than "normal" grout) can also be considered, but verify the strength/expansion characteristics as they may vary.

 

[dickwilber]

We had good results with a bituminous coating on either the concrete or the aluminum to maintain isolation and eliminate the formation of the growth salts which are so disruptive to the concrete. However, I would be concerned about reaction between the aluminum and the sulfur compounds in the municipal sewage, as well.

 

REPLY:
1. PRODUCT DESCRIPTION:

RUST GRIP is a one-part polyurethane coating that
combines with atmospheric moisture to cure. Upon curing,
RUST GRIP provides a protective coating of superior
adhesion, flexibility and abrasion/impact-resistance. It is
resistant to chemical solvents and acid splash. Originally
designed for metal surfaces, RUST GRIP demonstrates
excellent adhesion to wood, concrete, fiber glass and many
other substrates. RUST GRIP is designed for the
encapsulation of and adherence to tightly-bonded surfaces
of lead-based and other toxic paints as well as rusted
surfaces. This unique ability is accomplished by the curing
mechanism of the base polymer. The coating (having a low
initial viscosity) wets the rusty surface, then penetrates to
the foundation of the rust's origin where curing begins. The
polymer literally begins to swell, developing an interlocking
network between the pores of the surface and the coating.
RUST GRIP is highly recommended as a base coat for
SUPER THERM (liquid ceramic insulation). No pot life, no catalyzation, no
two-part mixing. Can substitute for zinc-rich primer
requiring no white sand-blasting. Can be applied over
rusted surfaces after loose/flaking material is removed.
High humidity quickens dry/cure cycle.

2. APPLICATION
Can power wash with solvent wipe down, light commercial
blast, or power hand tool to remove loose flake and debris
before applying. Can use power tool (within the guidelines
of Clean Air Act) with vacuum to prep lead-based paints
(as discussed at Steel Structures Painting
Council--SSPC--. meeting March 15-17 attended by
EPA and NIOSH) before applying RUST GRIP over
lead-based paints. Possible alternative to abatement of
lead paints. Surfaces should be clean, dry and sound.
Existing surface dirt, oil, tar, grease and film should be
removed from surface by approved methods
(TSP-Tri-Sodium Phosphate or equivalent) prior to
application of RUST GRIP. MUST BE COMPLETELY
DRY.

Salt Spray Corrosion Test: ASTM B117 @450
hours evaluation ASTM
Dl 654 over black steel.
Rating Procedure B:9
Key to Rating 0-10: ASTM D1654 0=
complete failure, 10=
excellent
Vehicle Type: Aromatic Polyurethane
Pigment Type: Aluminum
Gloss: Low angular sheen
VOC -- Rating: 414 gram/ ltr, California
EPA (Table of
Standards) maximum
accepted VOC allowed
is 500 grams/liter
under the classification of : "Metallic pigmented
coatings"
Viscosity: 15 seconds, #4 Zahn
Density: 9.18 lbs. per gallon
lmpact - Resistance: 200+psi Front side/l60
psi Backside
Abrasion-Resistance: ASTM (D4060) Graded
18, (excel lent) 18
milligram loss per 1000
cycles with the C517
wheel using a 1000 gram
load. Standard range of
loss is 100-150
milligrams per 1000
cycles.
Transmission of electrical currents: RUST GRIP does not
show any conduction until
18 volts. Important for
underground pipes and
tanks.

We also have a product that can restore the concrete (INNER SEAL).