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khoward (Mechanical) (OP)
18 Jan 01 15:56
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.
Helpful Member!  FSS (Structural)
18 Jan 01 18:26
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 (Civil/Environmental)
20 Feb 01 9:18
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.
Guest (Visitor)
20 Feb 01 16:05
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).  

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