Description / Abstract:
Purpose
This standard establishes definitions, guidelines, and
requirements governing the specific material (e.g., alloy and heat
treat condition) to be used for chemical process test specimens
when requirements call for "the same generic class of alloy".
Application
This standard has been used typically for plating and chemical
finishing processes, but usage is not limited to such applications.
Corrosion test specimens and hydrogen embrittlement test specimens
generally have specific test requirements and are excluded from
this document.
Background
Test samples utilized in metal finishing serve an important
function in assuring the quality and functionality of the plating
or coating produced. Some attributes of surface finishes can be
directly tested from actual parts that will see field service, and
the testing of actual plated/coated parts is always preferred.
However the testing of actual parts must always be nondestructive
in nature, that is, any tests that can alter, disturb or remove a
plating or coating will result ultimately in the rejection of the
test part from delivery. Since metal finishing by definition is a
topical plating or coating, many of the physical attributes of the
plating/coating can be easily, economically, and accurately
destructively tested using samples representative of the base metal
being processed. The selection of appropriate test sample material
and size establishes the foundation of quality acceptance of the
metal finishing process. When testing for the quality attributes of
the process, tests can be grouped in 3 categories:
a. Tests of the physical-dimensional properties of the actual
plating/coating: Examples of this can be general quality as
observed visually, microhardness, microthickness, wear resistance,
light fastness, residual stress, solderability, etc. Test sample
material is often specified to be of the same generic type as the
base metal, although test sample material differing from the base
metal being plated should not affect the outcome of this type of
test.
b. Tests of the coating/plating functionality: Examples of this
are adhesion, corrosion resistance, electrical resistivity, coating
weight, heat resistance, IGA-Surface attack, etc. Test sample
material is very important as this category test measures the
coating/plating relationships with the base metal.
c. Tests of coating/plating detrimental effects on the base
metal: An example of this is hydrogen embrittlement and test sample
material is of critical importance. Established industry testing
protocol for hydrogen embrittlement restricts test sample material
and heat treat condition. (ASTM F 519 is an example.)
Current industry standards and specifications allow separate
test specimens under certain conditions and the reader should refer
to the processing document specified by the procuring customer.
Generally accepted requirements state: "separate test specimens
shall be made of the same generic class of alloy as the parts,
distributed within the lot, cleaned, plated, and post treated with
the parts."
This document establishes policy for separate test specimen
material that is required to be of the "same generic class of
alloy" as the parts processed. While specimens of the same alloy
and heat treat condition are acceptable to represent the parts
processed, the materials listed herein have also found general
acceptance across the industry.