mars 2019

Surface Academy

Surface Testing

Surface Engineering

50 test methodsCorrosion & Coating properties

Our Market

Proton Technology, Bankeryd

Cooperation partners

Our Customers

Repositioning of test panels

during exposure – effect on

corrosivity of steel panels

Evaluation of reproducibility of

accelerated corrosion test –

ACT 1

ACCELERATED CORROSION TESTS

Accelerated corrosion testing is an essential tool for assuring

sustainability of parts and components that are exposed to

corrosive environments.

Many test methods have been developed and used over the

years.

Type of test

A Continuous salt spray tests

B Alternating exposure to salt solution or salt spray followed by drying

C Cyclic variation of humidity and including exposure of salt spray or rain

DContinuous exposure atmospheres with low concentration of corrosive gases at

moderately high humidity

EContinuous exposure atmospheres with higher concentration of corrosive gases at

higher humidity also with steps of drying and exposure to salt spray

F High humidity tests

From ISO/TR 16335 – Guidelines for selection of accelerated corrosion test for product qualification

From ISO/TR 16335 – Guidelines for selection of accelerated corrosion test for

product qualification

Field of

applicationSuitability of different categories of corrosion tests

Description

A

(Constant

salt spray)

B

(alternate

immersion/spray)

C

(humidity

cycling with

salt exposure)

D

(air pollutants)

E

(air pollutant,

drying and salt

spray)

F

(condensation)

Marine N U P P

Automotive N U P P

Building

constructionN U P P

Electric devices U* U* U* P P P

* For tightness

P: Preferred method

U: Useful for comparative tests of same product

N: Not useful unless for QC of same product

ACCELERATED CORROSION TESTS

Conclusively, the field of application determines what type of corrosion test

that should be chosen.

In many fields of application, tests using cyclic humidity and temperature with

intermittent salt exposure are being used more frequently. One of the main

reasons is that they often show good agreement with field exposures.

Salt spray tests may be used for process stability control of coatings for

cathodic protection. For product qualification, salt spray testing is not

suitable.

PURPOSE

The purpose with this study is to evaluate the

effect of periodic repositioning of the tested objects

during exposure.

The Accelerated Corrosion test method used is

described in e.g. Volvo STD 423-0014.

Standard test panels of CRS 150×70×1 mm were

used.

POSITIONS IN TEST CHAMBER

Initially, in each position (1-7) 2 sets of steel panels, A and B, respectively, with 3 panels in each set are positioned.

After each full cycle (one week), the set B panels are moved one position up (1→2, 2→3 etc).

The A set of panels are stationary during the full test.

After six weeks, the test is terminated and the weight loss due to corrosion is measured by dissolving the corrosion

products as per the method in ISO 8407 using 50ml/l HCl and 3,5 g/l hexamethylenetetramine as etchant.

2 15

6

7

3 4

↕ appr 10 cm↔ appr 10 cm

TEST CYCLE - ACT

Salt content. 1.0% ± 0.1%

pH 4.2 ± 0.1

Temperature deviation over the test plane

The temperature deviations were measured the last 5 minutes of a plateau before a ramp.

The conditions above are 35°C, 95 %RH and an empty test Cabinet.

This kind of data is very helpful to foresee corrosion scattering performance.

The temperature measurements were done by ControlArt in collaboration with Volvo Cars

RESULTS

Average metal loss ± std dev stationary panels: 162,7 µm ± 4,39 (2,70%) 1269 g/m² ± 34,2Average metal loss ± std dev repositioned panels: 160,0 µm ± 4,40 (2,75%) 1248 g/m² ± 34,3

163 160

0

20

40

60

80

100

120

140

160

180

Stationary Repositioned

µm

Metal loss

RESULTS

0

20

40

60

80

100

120

140

160

180

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Met

al lo

ss (

µm

)

Position

Stationary panels

1 2 3 4 5 6 7

Position

RESULTS

0

20

40

60

80

100

120

140

160

180

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Met

al lo

ss (

µm

)

Position

Stationary panels

0

20

40

60

80

100

120

140

160

180

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Met

al lo

ss (

µm

)

Position

Repositioned panels

1 2 3 4 5 6 7

Position

1 2 3 4 5 6 7

Position

Metal loss

It cannot be concluded that the repositioning has had an impact on the test result.

0

20

40

60

80

100

120

140

160

180

200

1 2 3 4 5 6 7

Met

al lo

ss (

µm

)

Position

Average metal loss per positionStationary

Repositioned

COMMENTS

• No significant difference between stationary and repositioned test panels.

• The purpose with this study was to evaluate the effect of periodic repositioning

of the tested objects during exposure. It cannot be shown that repositioning of test objects has any effect on the spread

in results in this type of chamber.

• It was also shown that the position in the chamber had no influence on the metal loss – the whole chamber can be used

• One cabinet only, one test period of six weeks

• Only steel panels, no zinc, no painted and scribed panels

• The cabinet had a low to medium load of parts. No parts were positioned closer than

10 cm from the test objects

• The cabinet was a ControlArt AB type TC210, installed during 2017.

• In future studies, similar measurements need to be performed in other cabinets, especially in cabinets produced by other

manufacturers.