ASTM D Test Method of Painted or Coated Specimens The purpose of the ASTM D test method is to provide a standardized procedure for the evaluation of corrosion performance of coatings and metal pretreatments subjected to one of a variety of corrosion resistance exposures. ASTM D describes the scribing of coated samples through the coating layer and into the substrate using one of a number of scribe tools. Following exposure, the samples are evaluated for corrosion resistance performance. The less corrosion creep on either side of the scribe, the higher the corrosion resistance performance.
|Published (Last):||4 December 2010|
|PDF File Size:||16.37 Mb|
|ePub File Size:||20.72 Mb|
|Price:||Free* [*Free Regsitration Required]|
A number in parentheses indicates the year of last reapproval. This standard has been approved for use by agencies of the Department of Defense. The values given in parentheses are for informationonly. It is theresponsibility of whoever uses this standard to consult andestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.
Referenced Documents2. Current edition approved Nov. Published December Originallyapproved in Last previous edition approved in as D — United States Significance and Use4. ANSI B See Fig. The tool bit is typicallymounted in a holder such as a wooden file handle to facilitatethe scribing operation. Typically thegripping surface is knurled. The tip may be replaceable orpermanent. Preliminary Treatment of Test Specimens6. This position will allow solution droplets to run lengthwisealong the scribe.
Position the tool sothat only the tip is in contact with the surface. Pullthe scribing tool to obtain a uniform V-cut through the coatingthat is being tested.
The endpoints of the scribe shall be at least1. Inspect the toolfrequently, using low power magnification, for dulling, chip-ping or wear and replace or repair as needed. The scribe shouldbe of sufficient length to cover the significant test area, butshould not contact the edge of the specimen. The scribe mustpenetrate all organic coating layers on the metal, leaving auniformly bright line.
The extent of scribe penetration throughmetal coatings, such as galvanize, should be agreed uponbetween the producer and user. The coil coating industrytypically requires scribes to penetrate all organic coating layersbut not penetrate the metal coating layers. The automotiveindustry typically requires scribes to penetrate all organic andmetal coating layers. The pencil type may be less effective thanthe lathe tool type when scribing coating systems consisting ofmultiple layers of organic coatings or coating systems includ-ing metal layers.
When scribing coating systems consisting ofmultiple layers of organic coatings or coating systems includ-ing metal layers the depth and quality of scribe techniqueshould be evaluated using the cross section, castable plasticmount, polishing technique described in Practice E3. Quality ofthe scribe technique may also be observed with the aid oflow-power magnification.
Note, mark, and describe defects,coding, and flaws that may affect results. If a motorizedcircular blade is used, position the test specimen to allow for astraight, linear cut at the desired length. The blade shall bepositioned to a depth such that it is able to cut into thesubstrate.
This type of blade will result in a rectangular cutrather than a V-cut. The use of more thanFIG. When multiple cuts are needed, each cut mustbe done in the same direction. If a motorized blade is beingused, it may be necessary to clean out residual materials of thescribe with a pencil-type scriber. Exposure of Test Specimens7. The lengthof test and evaluation intervals should be agreed upon prior toexposure of specimens. Remove coating along scribe with one of thefollowing methods such that all corrosion of the substrate thatis, rust creepage or undercutting can be observed using one ofthe following methods.
NOTE 1—The above methods may not be appropriate in all cases, suchas for interim ratings in continuing tests. NOTE 2—For all methods, complete the removal of loose coating with15 min of specimen removal from the exposure cabinet.
If removal cannotbe completed within the prescribed time, immerse the specimens in waterat room temperature or store in a plastic bag to avoid any drying effect. Record the maximumand minimum creepage from the scribe, and note whether ornot the maximum is an isolated spot. The mean can bedetermined by making at least 6 measurements of the width ofthe zone of corrosion uniformly distributed along the scribe,ignoring 3 mm 0.
As an alternative, use Test Method D Record creepvalues in millimetres, inches, or rating numbers as prescribedin Table 1, as agreed upon between producer and user.
Loss ofpaint that does not extend down to the substrate and result incorrosion can be rated using the same procedure, but shouldnot be considered as scribe creepage, undercutting, or corro-sion. If this is the case, not the coat s removed. Procedure B—Evaluation of Unscribed Areas9. Procedure C—Evaluation of Unprotected Edges Procedure D—Evaluation of Formed Areas Precision and Bias