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A number in parentheses indicates the year of last reapproval.
A superscript epsilon e indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. The wide variety of individual alloys and heat treatments under each group, the fact that certain adhesives exhibit speci? Procedures for aluminum alloys are well standardized, possibly because more bonding has been done with these alloys.
Preliminary tests should be conducted with the speci? This is especially true for stainless steel. It does not address the preparation of cast metals. The values given in parentheses are for information only. DuPont, Wilmington, DE The methods may be revised or supplemented, as necessary, to include methods based on proven performance. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applica- 1 This guide is under the jurisdiction of ASTM Committee D14 on Adhesives and is the direct responsibility of Subcommittee D Current edition approved Oct.
Originally published as D — Last previous edition D — 90 Generally in production, a series of tanks containing the necessary solutions is arranged with overhead cranes to transport parts to be prepared. Tanks should be lined with suitable materials to resist the solutions, and methods for circulating the solutions and heating with temperature controls should be included if required.
The use of a Series stainless steel for such equipment is suggested. Other metals may be used if they are resistant to the solution used. Rinsing may be done by spray or by dipping in a tank in which the water is circulated and constantly being renewed by an over?
After removing from any rinse the water-break test is commonly used. Other methods, such as indicator paper and contact angle, have been used to determine the effectiveness of the process.
Rinsing should be sufficiently long and vigorous to assure removal of soluble residue chemicals, or particles. The number of times a process may be repeated depends upon the amount of metal removed in relation to the tolerance requirements for the part and whether clad or bare metal is used. Generally, not more than two repeat treatments are permitted.
NOTE 1—No entirely foolproof method exists to determine bondability of a metal surface after preparation. Trial bonding followed by testing and evaluation against mechanical strength standards should be conducted to determine initial and continuous effectiveness of a method.
The useful life of solutions depends upon the number and size of the parts being prepared. Solutions should be sampled periodically and analyzed for materials pertinent to the particular treatment method, such as, titration for hexavalent chromium CrO3iron, chlorides, aluminum, etc.
A pH reading or acid content of trichloroethane vapor degreasing solution, or both, should be obtained. Standards should be established and records kept for such tests on each lot or vat of solution. Records should indicate the continuous conditions of solutions, such as amount of constituents added to bring solutions within limits, amount of contaminants present and date prepared see Methods D Usually, the time should not exceed 8 h and parts should be covered or wrapped in Kraft paper.
Prepared surfaces can change their characteristics on standing and adhesives vary widely in their tolerance of adherend surface conditions. In production bonding of complicated or large parts, the time interval may exceed 8 h. Investigation should be made to determine the time limitation of the adhesive and the rate of change on the surface of the adherend.
On the basis of the results of such an investigation, it may be possible to extend the length of time and establish standards for the interval between surface preparation and adhesive application to? Contaminating operations in the area should be avoided. Especially detrimental are paint or other spraying operations, processes using powdered materials, oil vapors from pumps and other machinery and spraying of mold release agents.
This can be accomplished by wiping with a cloth wetted with a variety of commercial solvents, such as acetone, methyl ethyl ketone, lacquer thinner and naphtha. Commercial vapor degreasing equipment is usually used. Parts are suspended in the vapor zone above the hot liquid and allowed to remain until there is condensation and run off approximately 5 min.
This step is repeated if necessary until all visible contamination is removed. The parts are raised above the tank and allowed to dry thoroughly. Previously bonded parts, such as honeycomb core materials, are usually not degreased due to difficulty in removing residue.
This test depends on the observation that a clean surface one that is chemically active or polar will hold a continuous? This is known as a water-break-free condition. A break in the water? Distilled water should be used in the test, and a drainage time of about 30 s should be allowed. Any trace of residual cleaning solution should be removed or a false conclusion may be made.
If a water-break-free condition is not observed on the treated surface, it should not be used for bonding. The surface should be recleaned until the test is passed.
If continuous failures occur, the treating process itself should be analyzed to determine the cause of the problem. Refer to the appropriate literature for details on cleaning techniques and procedures. Commercially available proprietary solutions may be used.
ASTM D2651 – 01(2016)
Material Sulfuric acid 6. Do not seal the anodized parts with boiling water before bonding. Do not allow the 2d651 interval between treatment and bonding to exceed 72 h, and cover or wrap all parts during the aastm with a non-contaminating vapor barrier material. Full-scale property tests should be run with the metal surfaces so prepared with the adhesive in question before accepting the process.
Satisfactory surface preparations have been accomplished by using paste-type etchants. These paste systems can be made by adding fumed silica to the sulfuric-dichromic acid solutions. The application of these paste systems allows for their use in fairly controlled areas.
The etching time is generally 10 to 20 min. Exercise extreme care to ensure removal zstm all traces of the etchant. A thorough rinsing with distilled water may be necessary to ensure complete removal.
Several commercial products are available. Some commercial compounds under the classi? Bond strengths obtained using either of these surface preparations are somewhat lower than those from the immersion processes. Aluminum oxide-impregnated nylon matting, glass-bead blasting and aluminum oxide cloth are typical acceptable abrasives.
Abrasive and debris should be wiped or water rinsed from the surface. The surface is the cathode. The surface is anodically etched again using astn wrapped electrode and a deep-etching solution.
E2651 rinsing should follow. The surface will exhibit a grey or lighter color. Initial treatment is at about 5 to 10 V. Finishing voltages from 15 to 25 V are used. Terminal voltages and current decay schedules are typically speci? Thorough rinsing follows, usually in warm to hot running water. Longer dwell times should be avoided.
Exercise care to ensure that all abrasive materials grit, sand, cloth, sand paper, or brushes are free from contamination that may be spread or rubbed onto the steel. Dry grit or sand blasting tends to warp thin sheet materials; these methods are suited only for thick-section parts.
Vapor blasting by water or steam and an abrasive is the most effective method and does not warp parts, if done carefully. Peening action of any blast process may work-harden the surface of some base metals. Hand sanding, rubbing with metal wool, and wire brushing are the least effective methods. Exercise care in using any mechanical method to prevent deep gouges or rough surfaces which are not conducive to good bonding.
Wash, vaporize degrease, r2651 brush or air blasted dry oil-free air surfaces to remove all traces of the abrasives. Apply the adhesive immediately after the treatment. This method should be used only in cases where other methods cannot be used. Somewhat lower bond strength results adtm this method compared to other methods asym.
Sand blast, grit blast, or vapor hone may be used. Thin sheet steel may be warped due to peening of the blasting abrasives. The major problem is in preventing oxidation of the surfaces.
Oxidation can occur in a very short time, even before the parts are dry. Parts must be bonded immediately. The adhesive or adhesive atsm must be applied immediately after drying. It produces a smut-free surface that can be treated by other chemical processes. Good bond strengths have resulted by bonding titanium alloys that have been anodized by proprietary processes. Procedure NOTE 3—The surface preparation methods for magnesium alloys are closely associated with corrosion prevention.
The high reactivity of magnesium requires that corrosion-preventative coatings be applied for most service applications.