AU2014100218A4

AU2014100218A4 - Method for improving the corrosion resistance of stainless steel mesh used to protect buildings from concealed termite entry

Info

Publication number: AU2014100218A4
Application number: AU2014100218A
Authority: AU
Inventors: Roger Franklin
Original assignee: TERMSTEEL Pty Ltd
Current assignee: TERMSTEEL Pty Ltd
Priority date: 2014-03-09
Filing date: 2014-03-09
Publication date: 2014-04-10
Anticipated expiration: 2022-03-09

Abstract

Woven steel mesh manufactured from strands of high grade stainless steel is widely used as a barrier to concealed termite entry in buildings. Although, stainless steel is generally regarded as highly resistant to corrosion, under adverse conditions stainless steel can corrode and compromise the integrity of the mesh barrier. This invention describes methods of polishing the stainless steel wire or mesh to reduce the likelihood of corrosion due to the presence of surface defects or surface contamination.

Description

EDITORIAL NOTE 2014100218 There are two page of description only There are approximately 30 species of termite in Australia capable of inflicting significant damage to timber structures and other wood-based building materials. Typically termite infestations are initiated from nests located in the ground outside the building structure. In the past buildings were protected from termite attack by treating the soil under and around the building with a chemical termiticide. This type of protection is generally known as a chemical barrier. Alternative methods of preventing termite attack that do not depend on the use of chemical termiticides involve placing a material impervious to termite attack around the perimeter of the building. Generally, the concrete slab itself forms part of the termite barrier or an impervious barrier is placed below the floor of the building. This type of protection is referred to as a physical barrier. In 1995 the building regulations were amended to allow concrete slabs constructed in accordance with Australian Standard AS2870.1 to be regarded as a physical barrier to entry of subterranean termites. In practice this means that only the perimeter of the concrete slab and slab joints where more than one slab is laid and service entry points need to be protected from termite ingress. For any barrier, other than a chemical barrier, to be placed under the concrete slab is difficult and costly to install. Consequently, this change to the building regulations paved the way for a variety of methods of protecting buildings from termite infestation. A number of physical systems have been developed to protect the perimeter and service points. These systems work by denying entry to termites other than by going around the barrier, where they can be detected by regular inspections. One commonly used physical barrier consists of woven steel mesh manufactured from strands of high grade stainless steel. The openings in the mesh are such that they are too small to allow termites to pass through and the steel itself is too hard for termites to penetrate. Steel mesh barriers are installed across all possible entry points such as perimeter cavities, service pipe penetrations, control joints, brick piers, etc. The mesh is bonded to the concrete/brick foundation using a termite proof parge such as bonding cement or epoxy adhesive. Stainless steel clamps are used to fasten the mesh around service pipes and other similar entry points. The parge material also forms part of the barrier and prevents termite entry because it is too hard for the termites to penetrate (analogous to the concrete slab barrier). The advantages of the stainless steel mesh system are obvious. Stainless steel is impervious to attack by termites, it is highly resistant to corrosion, and has a long history of use in construction as a stable construction material. Furthermore it is a system capable of eliminating all reliance on chemical termiticides. One disadvantage of stainless steel mesh is the tendency, under adverse conditions, for the stainless steel to corrode over time and compromise the integrity of the mesh barrier. While this is a comparatively rare occurrence, when it does occur it goes largely undetected.

This invention describes a simple method of reducing the likelihood of corrosion of the stainless steel mesh without resorting to the use of expensive, exotic grades of stainless steel or expensive coating materials that degrade over time. It is known that the presence of surface defects on stainless steel can increase its susceptibility to corrosion. Most surface defects are produced during fabrication. Defects can include embedded mild steel particles, scratches, heat tint, arc strikes, weld spatter, organic contaminants, etc. All of these surface defects have the potential to initiate corrosion that would not occur in their absence and can accelerate localised corrosion in aggressive environments. The wire from which stainless steel mesh is manufactured is polished prior to weaving into the final product. This process removes fine scratches, foreign material and other surface defects as outlined above considerably reducing the potential for the mesh to corrode under adverse conditions. Many methods of polishing stainless steel are known. These include but are not limited to electro-cleaning, electro-polishing, mechanical polishing including abrasive blasting, brushing, grinding and chipping. Electro-cleaning and electro polishing are the preferred methods of polishing stainless steel wire for manufacture of woven stainless steel mesh. Regardless of the method of polishing, the objective is to produce wire free from surface defects that increase the susceptibility of the stainless steel wire to corrode. It is also possible to form the wire into a woven mesh and then polish the wire to achieve the same net effect. This is most easily achieved using electro-cleaning or electro-polishing methods. Mechanical methods of polishing are less satisfactory when applied to the woven mesh but are capable of achieving the same reduction in the potential of the mesh to corrode. Stainless steel mesh used to protect buildings from concealed termite entry is typically constructed from 316 grade stainless steel. Many other grades of stainless steel may be used. This method of improving the resistance of stainless steel mesh to corrosion is applicable to all grades of stainless steel.

Claims

1. Manufacture of stainless steel mesh from polished stainless steel wire.

2. Polished stainless steel wire is any stainless steel wire that has been polished to remove surface defects that have the potential to initiate corrosion that would not occur in their absence and can accelerate localised corrosion in aggressive environments.

3. Methods of polishing stainless steel wire include but are not limited to electro-cleaning, electro-polishing, mechanical polishing including abrasive blasting, brushing, grinding and chipping.

4. Polishing of stainless steel mesh to remove surface defects that have the potential to initiate corrosion that would not occur in their absence and can accelerate localised corrosion in aggressive environments.

5. Methods of polishing stainless steel mesh include but are not limited to electro-cleaning, electro-polishing, mechanical polishing including abrasive blasting, brushing, grinding and chipping.

6. This method of improving the resistance of stainless steel mesh to corrosion is applicable to all grades of stainless steel.