Gary;
here's is an abbreviated version of a piece I posted previously;
Aluminum Cleaning:
To properly adhesive bond aluminum, the surface must be clean and chemically treated. The highest performance adhesive bonding includes degreasing and chromate conversion. Improper surface preparation is the major cause of adhesive bond failure.
Remove ink and markings from the surface of the aluminum with a light wash using MEK or acetone and white paper towels, followed by a degreasing (vapor phase degreasing preferred).
However a rinse using brake parts cleaner works well, which comes in spray cans and is available from most auto supply stores). Perform all of the above operations in a well-ventilated area (outside or fan blowing) and wearing a respirator.
Etch or chromate convert the surface using an Alodyne solution or a chromate conversion solution made from Iridite 14-2 (same thing). Immerse aluminum part for twenty minutes (at 70F or higher) or until the aluminum becomes a golden-brown color.
Rinse the metal thoroughly with distilled water and dry well. Do not use compressed air, because there is oil in most air compressors which will contaminate the clean surface.
If you do not wish to work with chromate solutions (I can provide a suggestion for safe disposal), you can use a phosphoric acid cleaner (Jasco Prep & Prime) to etch the aluminum surfaces which then passivates the aluminum with dichromate. Clean aluminum as above (no abrading) and immerse the aluminum in the Prep & Prime for thirty minutes (check time). Remove, rinse with distilled water (rain water – see note below) and air dry. All cleaned parts MUST NOT be touched by hand; use fresh, white cotton (mickey mouse style) gloves.
For best results, parts should be coated or bonded immediately after cleaning or chromate conversion. If you do not plan to bond the parts together within twenty-four hours, wrap in fresh ‘butcher’ paper to keep clean.
There are commercial companies that perform chromate conversion processing, and will provide this service on a tolling basis. Prior arrangements must be made to ensure the processed parts remain clean and suitable for adhesive bonding. This may be a way to go if a builder wants to use adhesives and obtain excellent corrosion protection.
Rinsing: Distilled water produces best results. However, rainwater caught from the roof is very low in mineral ions and is an acceptable substitute (discard the first five minutes of runoff – that is the roof rinse water & is dirty).
When working with chromic acid or Iridite solutions, wear nitrile rubber gloves (Harbor Freight – low cost). Also a long apron and shop face shield – safety first and last.
ALTERNATIVES:
Jasco Prep & Prime – caution, this contains both phosphoric acid and dichromates. Use full strength on aluminum at room temperature for thirty minutes, rinse well with distilled water and air dry.
Dupont Quick-Prep - Auto paint supply stores which sell Dupont paint. Quick Prep is a mixture of phosphoric acid and alcohol. When spread over bare metal it reacts with the surface to form a light coat of aluminum phosphate that prepares the surface for bonding. Most finishes can be applied directly over a surface that has been coated with metal prep. Quick-Prep is soluble in water and is generally only mildly toxic unless vaporized by heat. It is always advisable to wear nitrile rubber gloves and protect eyes from the irritating effects of contact.
Sherwin Williams Metal Prep - Auto paint supply stores sell Sherwin Williams paint. Metal Prep is a cleaner and conditioner for bare metal. It is composed of phosphoric acid and glycol ether. See Quick-Prep above for use directions.
Anko Phosphoric Acid Aluminum Brightener – This is available over the internet and is a cleaner and brightener for bare metal. It is composed of phosphoric acid and glycol ether.
All the best & fly safe,
MalcolmW
here's is an abbreviated version of a piece I posted previously;
Aluminum Cleaning:
To properly adhesive bond aluminum, the surface must be clean and chemically treated. The highest performance adhesive bonding includes degreasing and chromate conversion. Improper surface preparation is the major cause of adhesive bond failure.
Remove ink and markings from the surface of the aluminum with a light wash using MEK or acetone and white paper towels, followed by a degreasing (vapor phase degreasing preferred).
However a rinse using brake parts cleaner works well, which comes in spray cans and is available from most auto supply stores). Perform all of the above operations in a well-ventilated area (outside or fan blowing) and wearing a respirator.
Etch or chromate convert the surface using an Alodyne solution or a chromate conversion solution made from Iridite 14-2 (same thing). Immerse aluminum part for twenty minutes (at 70F or higher) or until the aluminum becomes a golden-brown color.
Rinse the metal thoroughly with distilled water and dry well. Do not use compressed air, because there is oil in most air compressors which will contaminate the clean surface.
If you do not wish to work with chromate solutions (I can provide a suggestion for safe disposal), you can use a phosphoric acid cleaner (Jasco Prep & Prime) to etch the aluminum surfaces which then passivates the aluminum with dichromate. Clean aluminum as above (no abrading) and immerse the aluminum in the Prep & Prime for thirty minutes (check time). Remove, rinse with distilled water (rain water – see note below) and air dry. All cleaned parts MUST NOT be touched by hand; use fresh, white cotton (mickey mouse style) gloves.
For best results, parts should be coated or bonded immediately after cleaning or chromate conversion. If you do not plan to bond the parts together within twenty-four hours, wrap in fresh ‘butcher’ paper to keep clean.
There are commercial companies that perform chromate conversion processing, and will provide this service on a tolling basis. Prior arrangements must be made to ensure the processed parts remain clean and suitable for adhesive bonding. This may be a way to go if a builder wants to use adhesives and obtain excellent corrosion protection.
Rinsing: Distilled water produces best results. However, rainwater caught from the roof is very low in mineral ions and is an acceptable substitute (discard the first five minutes of runoff – that is the roof rinse water & is dirty).
When working with chromic acid or Iridite solutions, wear nitrile rubber gloves (Harbor Freight – low cost). Also a long apron and shop face shield – safety first and last.
ALTERNATIVES:
Jasco Prep & Prime – caution, this contains both phosphoric acid and dichromates. Use full strength on aluminum at room temperature for thirty minutes, rinse well with distilled water and air dry.
Dupont Quick-Prep - Auto paint supply stores which sell Dupont paint. Quick Prep is a mixture of phosphoric acid and alcohol. When spread over bare metal it reacts with the surface to form a light coat of aluminum phosphate that prepares the surface for bonding. Most finishes can be applied directly over a surface that has been coated with metal prep. Quick-Prep is soluble in water and is generally only mildly toxic unless vaporized by heat. It is always advisable to wear nitrile rubber gloves and protect eyes from the irritating effects of contact.
Sherwin Williams Metal Prep - Auto paint supply stores sell Sherwin Williams paint. Metal Prep is a cleaner and conditioner for bare metal. It is composed of phosphoric acid and glycol ether. See Quick-Prep above for use directions.
Anko Phosphoric Acid Aluminum Brightener – This is available over the internet and is a cleaner and brightener for bare metal. It is composed of phosphoric acid and glycol ether.
All the best & fly safe,
MalcolmW