Chrome-Plated Surfaces

Determination of the Microcracked Chrome Deposit

Previous issues

PV 1058: 1973-04, 1999-12, 2004-12

Changes

The following changes have been made as compared to PV 1058: 2004-12:– Sections 3.2, 3.3, and 3.4 expanded

Scope

This standard describes a method for determining the microcracked chrome deposit on chrome-plated surfaces.

Description

Microcracked chrome deposit acc. to PV 1058

Test

Test equipment

A reflected light microscope with 100x to 200x magnification that has a dark field capacity in additionto the normal bright field capacity is required to determine the microcracked chrome deposit. In orderto count the microcracked chrome density, the microscope must either have etched measurementlines in the eyepiece or an image recording device that can be calibrated.

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3.1

Group Standard PV 1058Issue 2010-03

Class. No.: 50221

Descriptors: chromium, microcracked chrome deposit, chrome-plated, cracks

Check standard for current issue prior to usage.This electronically generated standard is authentic and valid without signature.The English translation is believed to be accurate. In case of discrepancies the German version shall govern.Numerical notation acc. to ISO practice.

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Technical responsibility Standards DepartmentGQL-LM/2 Dr. Anja Hasse Tel.: +49-5361-9-42106

GQL-LM/2 Günther Laudien

GQL-L Dr. Stephan EisenbergEKDV/4 Jürgen Wiesner EKDVTel.: +49-5361-9-29064 Manfred Terlinden

Confidential. All rights reserved. No part of this document may be transmitted or reproduced without prior permission of a Standards Department of the Volkswagen Group.Parties to a contract can only obtain this standard via the B2B supplier platform www.vwgroupsupply.com.© Volkswagen Aktiengesellschaft VWNORM-2008-12m

Etching solution

In order to be able to evaluate the microcracked chrome deposit, etching is common in most cases.The aqueous etching solution contains 85,0 g/l NaOH and 53,0 g/l K3(Fe(CN))6. Etching is omittedfor chrome-plated plastic parts with microcracks.

Procedure

The specimen part is cleaned with methylated spirit or acetone and viewed at 100x magnificationunder the microscope using the dark field. If the microcracked chrome deposit is clearly identifiable,the number of cracks per cm is counted using the measurement lines in the eyepiece or by meansof a calibrated recording.If the crack network cannot be clearly identified, the part must be etched and then viewed anew underthe microscope. The etching duration is approx. 20 min when the etching solution is unused and canbe extended to 15 h. If a microcracked chrome deposit cannot be clearly identified even after thisetching duration, then the etching solution is discarded, new solution is prepared, and the etchingprocess is repeated.Alternatively, anodic etching with a Couloscope® for 5 s at 0,5 A in 10% NaOH is permissible.Etched parts must preferably be evaluated at 100x magnification in the bright field. If the crack networkcannot be identified clearly with this method, 200x magnification must be used for the evaluation.

Test report

The counted number of cracks, the crack structure (e.g., incomplete, regular) if necessary, and theposition of the examined measurement areas must be indicated in the test report.Example: top of piston rod (according to drawing specification) 600 to 800 cracks/cm, partially in‐complete.

Explanations of the images (magnification = 100 : 1)

Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, and Figure 6 show typical unacceptable microcrackedchrome deposit structures and microcracked chrome crack densities.Figure 7 shows an irregular microcracked chrome deposit that is the cause of a complaint but is stillaccepted.Figure 8, Figure 9, Figure 10, and Figure 11 show microcracked chrome crack densities that areevaluated as being OK.

3.2

3.3

3.4

3.5

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Figure 1 – Irregular microcracked chrome deposit,< 100 to 400 cracks/cm

Figure 2 – Irregular microcracked chrome deposit,< 100 to 200 cracks/cm

Figure 3 – Incomplete microcracked chrome de‐posit

Figure 4 – Individual crack

Figure 5 – Overly coarse microcracked chromedeposit, < 100 cracks/cm

Figure 6 – Overly fine microcracked chrome de‐posit, > 1 000 cracks/cm

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Figure 7 – Irregular microcracked chrome deposit,approx. 200 to 400 cracks/cm

Figure 8 – Complete microcracked chrome de‐posit, approx. 250 to 400 cracks/cm

Figure 9 – Complete two-layer microcrackedchrome deposit, approx. 300 to 400 cracks/cm in

the upper crack layer

Figure 10 – Complete microcracked chrome de‐posit, approx. 400 to 600 cracks/cm

Figure 11 – Complete microcracked chrome deposit, approx. 600 to 800 cracks/cm

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