The science of wood preservation is the treatment of wood to increase durability and give extended service life. There are timber structures still in existence after hundreds of years of service, but there are also fence posts which have rotted after only 18 months of service.
The effectiveness of any type of preservative treatment depends on the penetration achieved and the retention of preservative in the penetrated zones. Correct methods in the application of preservatives must be used to ensure proper timber treatment practice.
Applying the Tanalith® C or CCA treatment (Chromated Copper Arsenate) to timber enhances the durability by preserving it against biological deterioration such as wood destroying fungi, insects and weathering conditions. It has a proven track record of being effective against organisms by rendering the treated wood fibre useless as a food source for fungi, termites and woodborer.
The CCA preservative is applied by vacuum pressure impregnation and solution concentration can be varied according to the desired retention. It is both a fungicide and an insecticide. The chrome acts as a fixing agent, reacting in the presence of wood cellulose to render the CCA preservative insoluble and therefore do not contaminate ground water or soil with harmful leachates.
This method ensures that the wood preservative penetrates and is retained within the wood cell structure. Some of the predominant characteristics that sets Tanalith® C products apart as a viable alternative option is that it is odourless, it does not leave an oily residue, it does not need to be rotated during storage, its low conductivity protects against current leakage and its low corrosiveness makes it compatible with a wide range of metal fittings.
In South Africa, all Tanalith® C treated timber products must be treated according to SANS 10005 – The Preservative Treatment of Timber and meet the product SANS 457 product specifications for timber poles, droppers, guardrail poles and spacing blocks for Pine poles (SANS 457-2) and Eucalyptus poles (SANS 457-3).
To achieve the desired performance, the wood preservative must be applied in compliance with the correct requirements for penetration and retention in order for the treated wood to deliver the performance expected of it. Products that are not treated to standard, including those produced without quality procedures, with superficial systems such as dip treatments, or those treated using wet timber will not provide the durability and longevity of a properly preserved pole.
Freshly treated CCA timber is identifiable by its yellow/greenish to green colour that fades over time into a weathered silver-grey if exposed to the elements and not maintained with a wood finishing protective product i.e. a suitable exterior sealer. CCA treated wood is highly resilient against attack from biological decay and organisms if correctly applied.
Quality treated CCA timber is identifiable by doing a CCA penetration test. This is be done by using an increment borer and obtaining a 30mm sample from the treated timber and spraying it with Tanalith® indicator. The sample should show at least 15mm penetration into the treatable zone.
The penetration refers to the depth at which the chemicals enter the wood. The depth of penetration is dependent on the cut and species of the wood being treated. Additionally, the deeper the treatment penetrates, the more effective and long-lasting the preservative treatment will be. Retention is usually expressed as kilograms of preservative per cubic meter of wood (pounds per cubic foot), which is the amount of preservative retained in the wood after completion of the treatments and is one measure of the degree of protection provided.
The degree of protection required is dependent on the various elements the timber will be exposed to. South Africa utilizes a Hazard class system grouping various applications of treated timber by the exposure of elements the timber faces; this will determine the amount of Tanalith® C CCA required effectively protecting the timber and prolonging the life of the Timber.
For example:
- Hazard Class 2 (6kg per m3): Interior aboveground eg: roof trusses, purloins and battens, framing timber.
- Hazard Class 3 (8kg per m3): Exterior above-ground eg: decking joists, bearers and decking boards, external cladding, garden furniture, balustrades, walkways, fence battens, trellises.
- Hazard Class 4 (12 kg per m3): Exterior in-ground eg: fence and agricultural posts, garden edging, pergolas, landscaping material.
- Hazard Class 4V (16 kg per m3): Vineyard timbers e.g. vineyard poles.
- Hazard Class 5 (16 kg per m3): Exterior in fresh water e.g. house piling, retaining walls, fresh water jetties, flood irrigated vineyards.
- Hazard Class 6 (20 kg per m3): Marine timbers e.g. marine piling, slipways, timber in seawater (dual treatment with TANALITH®C and creosote).
Tanalith® C has been the standard bearer of water-based wood preservatives since 1933 and is a globally recognised brand that has a proven successful history, when applied to standard in good quality timber. This is backed by laboratory and field tests. It also has a certified 20 to 25 year lifetime (minimum) with a 15-year guarantee against insect attack and fungal decay.
Source: Lonza
The information contained herein is believed to be correct and corresponds to the latest state of scientific and technical knowledge. However, no warranty is made, either expressed or implied, regarding its accuracy or the results to be obtained from the use of such information. Some products may not be available for every type of application. Any user must make his own determination and satisfy himself that the products supplied by Lonza Wood Protection and the information and recommendations given by Lonza Wood Protection are (i) suitable for intended process or purpose, (ii) in compliance with environmental, health and safety regulations, and (iii) will not infringe any third party’s intellectual property rights.
About Lonza
Lonza is a leading global supplier to the pharmaceutical, biotech and specialty ingredients markets. We work to promote a healthier lifestyle and prevent illness by supporting our customers to deliver innovative medicines that help treat or even cure a wide range of diseases. This is complemented by our broad range of microbial control solutions, which help to create and maintain a healthy environment.
Patients and consumers benefit from how we apply our scientific knowledge and advanced manufacturing technologies to the healthcare, hygiene and fast-moving consumer goods markets and to developing preservation and protection materials. Founded in 1897 in the Swiss Alps, Lonza today is a well-respected global company with more than 100 sites and offices and approximately 15,500 full-time employees worldwide (at the end of 2019). The company generated sales of CHF 5.9 billion in 2019 with a CORE EBITDA of CHF 1.6 billion. Find out more at www.lonza.com.
