shell treated wood approach€¦ · john ruddick 2007 4 cumulative amount (mg/m2) of copper leached...

John Ruddick 2007

1

Alkaline Copper Treated Wood for Residential Use

University of British Columbia Professor John Ruddick

ObjectivesInvestigate:

How shell treatments work in treated wood exposed above ground;

The factors influencing the migration of copper in amine copper wood preservative treated decking

Monitor depletion during natural weathering

Preservative mobility in decking

2 - 4 mm

Typical lumber yard production

Shell treated wood Approach

Isolate fungi from exposed CCA treated decking after 10, 15 and 20 years Identify fungiRecover samples for chemical analysisConfirm the difference between spore and mycelial tolerance

Possible explanations for good performance of CCA shell treated wood used above ground

Limited moisture content

High proportion of heartwood

The role of minor amount of mobile CCA preservative

Check –main avenue for fungi to access treated wood used above ground

John Ruddick 2007

2

Treated surface

Unfixed chemical

Checks

Spore germination in above ground wood Migration of chemical onto check surface

Spore

Spore germination in above ground wood Decay of treated decking associated with checks

Externally Sound

Fruiting body on decking

Minimum Inhibitory Copper Concentration(on agar media)

0

5

10

15

20

25

30

35

40

45

1 2

Cu c

once

ntra

tion

(mM

)

Mycelia Basidiospores

40

0.242.4

24

0.24

0.72 0.12 0.12

Oligoporus placentus

Gloeophyllum sepiarium

0

5

10

15

20

25

30

35

40

45

1 2

Cu c

once

ntra

tion

(mM

)

Mycelia Basidiospores

40

0.242.4

24

0.24

0.72 0.12 0.12

Oligoporus placentus

Gloeophyllum sepiarium

Approach

Install pressure treated boardsSection to provide samples for chemical analysis and field exposureSections for field exposure are approximately 300 mm longSupport two 2 x 6 samples or three 2 x 4 samples over basins and collect run off

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Chemical analysis

• Treated surface of reference section removed using a computerised routing system

• Analysed by x-ray spectroscopy to provide reference retention

• Penetration of the copper determined for each surface, including end penetration

Chemical analysis

Factors being examined

• Wood species• Preservative retention• Preservative penetration• 2 x 4 vs 2 x 6• Treated vs untreated ends• Water repellants• Pressure wash• Redistribution into checks

Preservative mobility in decking

Monthly amount (%) of copper leached - ACQ

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

Aug-02

Sep-02

Oct-02

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Dec-02

Jan-03

Feb-03

Mar-03

Apr-03

May-03

Jun-Jul03

Aug-03

Sep-03

Oct-03

Nov-03

Dec-03

Jan-04

Feb-04

Mar-04

Apr-04

May-04

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Jul-04

Aug-04

Month

Am

ount

of c

oppe

r (C

uO) l

each

ed p

er M

onth

(%)

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Leac

hate

(ml)

CuO leached (%) Leachate (ml)

Influence of the environmental conditions in the field leaching

• Amount Cu Leached = f (time of exposure, volume of leachate, sun hours, temperature)

• Cu leached(mg)=12.573-3.347T+0.003V+0.55S-0.923Temp.Where: T: time of exposure in months

V: volume of leachate (ml)S: sun hoursTemp: Temperature

Coefficient of determination: R²=0.74At retention of 5.21 kg/m3

John Ruddick 2007

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Cumulative amount (mg/m2) of copper leached after 4 years exposure - ACQ

0

1000

2000

3000

4000

5000

6000

Aug-02Sep-02Oct-02Nov-02Dec-02Jan-03Feb-03Mar-03Apr-03May-03Jun-Jul03Aug-03Sep-03Oct-03Nov-03Dec-03Jan-04Feb-04Mar-04Apr-04May-04Jun-04Jul-04Aug-04Sep-04Oct-04Nov-04Dec-04Jan-05Feb-05Mar-05Apr-05May-05Jun-05Jul-05Aug-

Sep 05Oct-05Nov-05Dec-05Jan-06Feb-06Mar/Apr

- 06May-06Jun-06Jul-066-Aug6-Sep

Months

Cum

ulat

ive

amou

nt o

f cop

per

(as

CuO

) lea

ched

(mg/

m²)

0

50

100

150

200

250

300

350

Prec

ipita

tion

(mm

)

Cumulative amount of Cu Precipitation (mm)

Final vs Initial losses after 2 years exposure

y = 253.48x0.4268

R2 = 0.8308

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 200 400 600 800 1000

Initial (mg/m²)

Fina

l (m

g/m

²)

Final vs Initial losses after 4 years exposure

y = 503.21x0.3743

R2 = 0.7877

0.00

1000.00

2000.00

3000.00

4000.00

5000.00

6000.00

7000.00

8000.00

0.00 200.00 400.00 600.00 800.00 1000.00 1200.00

Initial (mg/m2)

Fina

l (m

g/m

2 )

0

500

1000

1500

2000

2500

Jun-Jul-03 Aug-03 Sep-03 Oct-03 Nov-03 Dec-03 Jan-04 Feb-04 Mar-04 Apr-04 May-04

Cum

ulat

ive

amou

nt o

f cop

per (

mg/

m²)

Jack pine Hem fir Lodgepole pine

Cumulative amount (mg/m2) of copper leached – CA-B

Cumulative amount (mg/m2) of copper leached after 3 years – CA-B

0

1000

2000

3000

4000

5000

6000

Jun-J

ul-03

Aug-03

Sep-03

Oct-03

Nov-03

Dec-03

Jan-0

4

Feb-04

Mar-04

Apr-04

May-04

Jun-0

4Ju

l-04

Aug-04

Sep-04

Oct-04

Nov-04

Dec-04

Jan-0

5

Feb-05

Mar-05

Apr-05

May-05

Jun-0

5Ju

l-05

Aug-Sep-0

5Oct-

05

Nov-05

Dec-05

Jan-0

6

Feb-06

Mar/Apr-0

6

May-06

Jun-0

6Ju

l-06

Aug-06

Sep-06

Cum

ulat

ive

amou

nt o

f cop

per l

each

ed (m

g/m

²)

0

50

100

150

200

250

300

350

Rai

nfal

l (m

m)

Jack pine Hem firLodgepole pine Rain

Leaching of copper

Cu

Unfixed copper leached from the surface

Cu

Surface content is depleted during initial rain events

John Ruddick 2007

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Leaching of copper

During drying mobile copper moves to the surface

Cu

During further rain events mobile copper at the surface is

moves into checks or is leached

Migration of copper into checks

CA-B – hem-fir • Avge. 0.43 mg Cu/g wood

(0.26 – 0.54 mg Cu/g wood )ACQ – hem-fir• Avge. 0.49 mg Cu/g of wood

(0.47 – 0.52 mg Cu/g woodCCA – hem-fir• Avge. 0.29 mg Cu/g wood

Corrosion of fasteners and connectors used in contact with alkaline copper treated

wood – the real world

Objectives• Investigate the performance of

commercial fasteners and connectors in contact with alkaline copper treated wood

• Evaluate field performance of fasteners and connectors

Corrosion of fasteners and connectors in contact with treated wood

What is corrosion?

• Metals react with oxygen in the presence of water to form oxides.

• The problem with iron (and many metals) is that the oxide formed does not attach well to the metal surface.

• It flakes off easily causing “pitting” which weakens the fastener.

What is corrosion?

• The amount of water complexed with the iron controls the colour of rust.

• It may be black to yellow to orange brown (red).

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Wood is corrosive to metals

Factors affecting iron reactions are• Tannin content• pH• Moisture Content • Oxygen• Temperature

Treated wood

Factors affecting corrosion in treated wood• Same as untreated plus-• Corrosion inhibitors (Cr, As etc.)• Residual solvent (ammonia, amine, acids, etc)• Mobile noble metal e.g. copper

How do we control corrosion?

• Organic and Inorganic coatings

• Metallic coatings

• Combination coatings

How do we test fasteners?

Materials

• ACQ treated wood purchased from local Home Depot stores

• CX and ACQ supplied from commercial treatment• CCA wood samples purchased from Home

Hardware, Vancouver• Nails selected for the corrosion research based on

suppliers recommendation as suitable for alkaline copper treated wood

Fasteners before exposure

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Fastener preparation

Nails hammered into wood and removed by carefully splitting wood

Nails weighed before placing in the sandwiched samples

Effects of mechanical action

Fasteners placed in wood sandwich Climate conditions

• Harshaw Environmental chamber 0.7 x 0.76 x 1 m

• Water temperature – 32 °C• Water mist pressure – 10 Pa• No direct spraying of fastener heads• Continuous misting except during evaluation

Evaluation of Corrosion Level • Visual Observation (ASTM D610-01 based on

white rust and red rust formation. 100% red rust = 100 %)

• Weight Loss • Diameter Loss (Steel Core Cross-Section

Reduction)• Pit depth• Bending Yield Strength Testing

Evaluation Protocol Treated wood

• ACQ treated spruce• CCA treated hem-fir• ACQ treated lodgepole pine• CX treated hem-fir• Western red cedar

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Visual Results Bright – 830 hrs

• CCA

• ACQ

Visual Results - hot dipped Zn – 830 hrs

• CCA

• ACQ

Weight loss

• Weight Loss.• Ultrasonic Bath used to clean the

corrosion Products.• Less accurate than diameter

measurement due to difficulty of removing corrosion products.

Weight loss CCA vs ACQ

0

5

10

15

20

25

30

Magni #599HG + Ph

Stainless steelPT 2000

Weather Beater

Alumoweld HG

Bright nail

Wei

ght l

oss

%

Weight loss - ACQ Weight loss in CCA"

Diameter loss (%)

• Diameter loss (Steel Core Cross-Section Reduction)

• Measured with Caliper to 0.0025 mm• Can also be used to calculate cross sectional

area loss• Fails to assess pitting corrosion – pit depth

Diameter loss (%)

0

2

4

6

8

10

12

14

16

Magni

#599

HG + Ph

Stainle

ss st

eel

PT 2000

Weathe

r Bea

ter

Alumno

weld

Hot dip

ped

Bright

Dia

met

er lo

ss (%

)

ACQ

CCA

John Ruddick 2007

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Influence of water repellants on ACQ spruce – weight loss

0

2

4

6

8

10

12

Hot dipped Hot dipped+phosphate

Bright

% w

eigh

t los

s

% weight loss in ACQ + WR% weight loss ACQ

Visual corrosion rate ACQ+WR

0

20

40

60

80

100

188hrs 387hrs 575hrs 811hrs 1000hrs 1188hrs

Red

rust

gra

de (%

)

Bright Hot dippedPG MagniDeck screw Stainless

What happens in the real world and why? What happens in the real world and why?

• Incorrect fasteners and connectors– Common nails– Electroplated galvanized nails– Aluminum connectors– Inadequate barrier coatings

What happens in the real world and why?

Red rust on common iron fasteners

Incorrect fasteners


Electroplated zinc coated

Incorrect connectors

John Ruddick 2007

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• Incorrect fasteners and connectors• Incompletely fixed copper in alkaline

copper treated wood


Copper deposits on wood surface, but no watermarking, suggesting reaction with unfixed copper in wet wood


White rust

copper deposits Red

rust

Red rust


Red rust on G185 connector from ACQ treated wood

Copper plated onto

fasteners



copper treated wood• Red rust formed on unprotected edges of

G185 connectors– Will this red rust lead to accelerated corrosion of

galvanized face?


John Ruddick 2007

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White rust over surface and on

fastenersRed rust

Moisture on wood


Damage to heads and shank during nailing?



copper treated wood• Red rust formed on unprotected edges of

G185 connectors• Surface loading of copper due to

perceived end use or incising


Copper deposits and white rust

Incised lumber


• Not all fasteners or connectors corrode


Good performance

John Ruddick 2007

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Good performance

Real world

Alkaline copper treated wood is more corrosive than CCA treated woodSome connectors with G185 galvanizing showed red rust in less than 2 yearsRed rust was found on some galvanized connectors, even though no signs of wetting, suggesting mobile chemical in wet wood when delivered was causing corrosionIncised lumber appeared more corrosive than unincised lumber

Real world

• Fastener heads appeared susceptible to damage of the galvanizing during hammering resulting in corrosion

• Aluminum connectors, brackets, and flashing should not be used in contact with alkaline copper treated wood

• Lack of fixation of alkaline copper treated wood prior to use, will increase corrosion

But will they give 20 years?

Hot dipped galvanised nails after 20 years in CCA decking

Acknowledgements

• Newsha Ashari• Baekyong Choi• Sungmee Choi• Pablo Chung• Sofya Soldkin – Tree Island Industries

• Homeowners Protection Office of BC• Arch• Viance (CSI)• Dr. Wolman GmbH

shell treated wood approach€¦ · john ruddick 2007 4 cumulative amount (mg/m2) of copper leached...

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