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Hot Dip Galvanizers Association Southern Africa, 3 Riley Road, Bedfordview (2025)

05/11/2025

Connecting with the steel supply chain on the safety and structural integrity of hot-dip galvanized fasteners

Hot-dip galvanizing, a tried and tested technology which provides barrier protection and cathodic corrosion protection, ensures safety and structural integrity when applied to fasteners.

Although South Africa has the capability and capacity to manufacture these, volumes remain small. A clearer understanding of the benefits of hot-dip galvanizing fasteners - as well as the knowledge of and adherence to stringent industry standards - could grow the market and benefit the entire supply chain, says Robin Clarke, Executive Director of the Hot Dip Galvanizers Association of Southern Africa (HDGASA).
The nuts and bolts of hot-dip galvanising
The conventional method of hot-dip galvanizing, jigging components onto a flight bar and dipping them into molten zinc, is not feasible for small fasteners. Instead, they are placed in perforated baskets for hot-dip galvanizing, and then transferred to a centrifuge to spin off any unreacted zinc. This leaves a carefully controlled amount of zinc on the fastener with very good definition in the threaded area.

For the hot-dip galvanizing of fasteners, the HDGASA supports and promotes adherence to the ISO 10684 and the SANS 121:2024 / ISO 1461:2022 standard. These specify a minimum coating thickness of 50 microns for threaded articles with a diameter exceeding 6mm; and 25 microns for those with diameters equal to or less than 6mm.

Clarke emphasises that engineers design structures with sufficient strength to perform their functions: “Corrosion control is integral to strength calculations. The use of the correct fasteners, particularly in a structural steel environment or highly corrosive climate, is critical. The considerations applied to corrosion control of nuts and bolts should, at all times, equal those applied to the main structural members.”
Fastening on to the benefits
A common misconception among users is that any zinc-coated item is hot-dip galvanized: “Hot-dip galvanizing produces a significantly thicker zinc coating than zinc plating. Often fasteners specified as hot-dip galvanized are supplied as zinc-plated, resulting in reduced durability due to thinner coatings,” Clarke observes.

A zinc-plated fastener typically has a coating thickness of around 10 microns, which is 2.5 to 5 times thinner than the minimum specified in hot-dip galvanizing standards. It follows that hot-dip galvanizing offers a 2.5 to 5 times greater level of corrosion control and service life.

Clarke also warns against using stainless steel fasteners to connect hot-dip galvanized steel components: “This mismatch of materials creates a galvanic corrosion cell which accelerates corrosion of the hot-dip galvanized component. In fact the hot-dip galvanized component sacrifices itself to protect the stainless-steel nuts and bolts. The hot-dip galvanized steel retreats from the stainless steel, giving the incorrect impression that the hot-dip galvanized coating has failed.”
Price and aesthetics are also challenges, with the thin coating on a painted article appearing more attractive and more cost-effective. Clarke concedes that, with South African construction supply chains under pressure, there is always a temptation to resort to cheaper options, without sufficiently considering how these will perform from a safety and quality perspective.

Connecting over challenges
Furthermore, Clarke points out that concerns surrounding hot-dip galvanizing of high tensile nuts and bolts which exceed a 1 000 mega Pascals (MPa) tensile strength rating are to be re-evaluated: “While it is perceived that these are prone to hydrogen embrittlement during the galvanizing process and should not be hot-dip galvanized, German companies are hot-dip galvanizing tensile fasteners at volume. This is done by mechanically cleaning fasteners and flash pickling them, to minimise the potential for hydrogen ingress into the fastener,” he explains.

He also mentions that correct storage and handling of hot-dip galvanized fasteners is imperative. These should be stored and delivered to site with the nut secured onto the bolt:
“The torqueing of hot-dip galvanized fasteners is usually done by the ‘turn of the nut’ method. The method of fastening is to turn the nuts to achieve a snug fit between plies. Once that is done, the nut is marked and then turned (depending on the size and length of the nut and the bolt) by a further third to two-thirds full turn.

Correctly hot-dip galvanized fasteners play an integral role in the ‘nuts and bolts’ of durable, successful steel construction: “The HDGASA is committed to working with our members and the wider steel supply chain, to ensure the quality and standards of hot-dip galvanized fasteners, through the provision of guidance, technical education and advisory services,” Clarke concludes.

03/11/2025

Regalvanizing: cornerstone of the circular economy, says the HDGASA.
Steel can be regalvanized three to four times, effectively doubling the lifespan of key infrastructure for 30% of the replacement cost. That is why the Hot Dip Galvanizers Association of South Africa (HDGASA) sees regalvanizing as a cornerstone of the circular economy.

HDGASA Marketing Manager Anthony Botha notes that the circular economy challenges the linear ‘take, make and dispose’ manufacturing model - and goes beyond traditional recycling: “This involves melting and reprocessing, which consumes significant energy. However, regalvanization is just cleaning and recoating the existing steel with zinc, to restore corrosion resistance - without the energy- intensive rebuilding of an entirely new structure,” Botha explains.

“Regalvanizing is no longer optional. With the challenges facing the industrial sector, it is a powerful strategy for extending the lifespan of steel. Materials of construction are running out, and industries must start reusing and regalvanizing. Rather than discarding ageing steel components or articles, we need to ensure these have a longer service life. That way, we preserve embodied energy and minimise waste,” he advises.

Stripping and cleaning

According to Botha, the process begins with a thorough inspection by the galvanizer, to ensure that an article can be regalvanized either for continued use or for reuse elsewhere: “Regalvanized components must retain their inherent structural tolerances, especially if these are used in load-bearing applications. This will ensure durability congruent with the environment in which the regalvanized material is to be employed.”

Key considerations include steel chemistry – including the silicon content when first fabricated, as this will reduce during preparation for regalvanizing – as well as the overall surface condition and dimensional integrity.

Components are then stripped of old coatings. The galvanizer will have to remove any coating of existing zinc, rust, any other oxides, contaminants or paint either by abrasive blasting and/or chemical cleaning.

Botha emphasises that the steel surface plays an important role in achieving a quality coating. Cleanliness is paramount when it comes to the final step, which is fluxing.

“After coating acceptance, the regalvanized article will be inspected as per any other galvanizing in accordance with SANS 121:2024 (ISO 1461:2022). This is exactly the same process and methodology used for brand new articles,” he notes.

Infrastructure renewal

Botha explains that regalvanizing is gaining traction in the refurbishment of utility structures and modular infrastructure by South African and neighbouring countries’ state-owned enterprises (SOEs): “Many do not have hot dip galvanizers in their countries. They disassemble and then send it to South Africa for regalvanizing. This is typically reusing existing steel elements for everything from road furniture to signs, gantries, and lattice towers. This reduces the procurement cost of steel and shortens the lead-time because there is no fabrication requirement.”

Overall, hot dip galvanizing provides a far extended lower cost over the entire lifespan of the structure.

Duplex coating, when a galvanized article is painted with a zinc compatible coating to provide extra protection, can also be repeated after steel is stripped, cleaned and then regalvanized.

Economic and environmental spin-offs

“From an economic standpoint, regalvanizing can cut costs by up to a third. This is important, especially when logistics and lead-times are factored into overall infrastructure costs.

When extending the service life of a structure, regalvanizing can completely change the way that the industrial sector looks at maintenance,” Botha adds.

He reiterates that a structure can be successfully regalvanized several times over a 20-year period, as long as the properties of the steel are preserved. The first maintenance is due when 5% of the entire surface area shows red rust, as galvanizing, whilst still providing corrosion control through cathodic protection, experiences increased rates of depletion.

“As infrastructure owners and engineers embrace circularity, galvanizing stands out as a practical, standards-compliant, and economically sound solution. It bridges the gap between sustainability and operational realities: to deliver corrosion control, protection, cost-savings, and environmental stewardship, all in one elegant process. In short, this is not just a technical fix, but a strategic pivot towards more resilient and resource-efficient futures,” Botha concludes.

02/09/2025

The HDGASA galvanizes micro-enterprises to learn and grow
The Hot Dip Galvanizers Association of South Africa (HDGASA) has a distinctive ‘open door’ approach when it comes to educating and equipping micro-enterprises – small businesses - to embrace hot dip galvanizing, the widely preferred method of corrosion control for steel.
“A great oak tree does not grow overnight. As an industry, we must remember that the great oaks of tomorrow are just saplings today,” says HDGASA Marketing Manager, Anthony Botha.
“In South Africa, youth unemployment is currently sitting at approximately 60%. Government is looking at youth training programmes such as welding and metalworking. People will use these skills for their own entrepreneurial pursuits. Others may have already developed skills in fabrication or manufacturing, and are now trying to set up their own businesses. Despite having had some exposure, they may not yet fully understand the technology,” Botha points out.
The HDGASA provides technical support to micro-enterprises online via the Association’s website and responds to phone and email enquiries - providing what Botha calls “ground-level entry to education on galvanizing” for the entrepreneur who may be working out of his home garage or a small factory unit.
Guidelines can be easily downloaded and are written not only for technically qualified people such as engineers, but for non-technical entrepreneurs, who are looking for practical information and advice about hot dip galvanizing as a means of corrosion control.
Supply and demand
In certain parts of the country where corrosion is high, there is already significant demand for galvanizing - even from small businesses or semi-professional DIY businesses making steel articles such as gates, burglar proofing, fencing or trailers.
“However, to optimise the protection provided by galvanizing, micro-entrepreneurs must understand their role: for example, inserting venting and drainage holes, as well as other technical requirements,” Botha points out.
He adds that micro-enterprises should understand that hot dip galvanizing is a final phase in the downstream supply of steel products. It is therefore a finishing, rather than an applied coating: “It is not paint, or something that you can take and put on yourself. There are some misconceptions around what the market perceives as ‘cold’ galvanizing. This refers to a zinc-rich paint, applied to very small items in non-aggressive environments. With hot dip galvanizing, an item is dipped into a kettle of molten zinc at 450°C. There is a significant difference in the outcome.”
A two-pronged approach to protection
Botha notes that the end-user also requires education: “The person bringing in the work is not necessarily the one who gets to use the product. So the galvanized gate, the boat anchor; the burglar proofing or fencing is used by another party. This is about protecting both the business owner and their customers. It is a two-pronged approach.”
He stresses that the quality of galvanizing is driven by the steel itself. Once an article has been made, the dye is cast and there is very little that a galvanizer can do.
Different types of steel have a different chemical composition, which reacts with the zinc to give it a certain appearance. This varies from bright, shiny, silvery galvanizing to a dull grey. Corrosion control is the primary focus - with aesthetics being a secondary consideration.
Paint can be applied to galvanized steel - but again, the right choice of paint and preparation is essential: “We supply a lot of information on our website about how to prepare galvanizing for a paint coating. Once again, it comes to communicating, coordinating and cooperating around the galvanizing of an item.”
Botha says it is important for the small business to ask the big questions and to “be its own policeman” when it comes to quality control: “Small businesses should not only understand what they are dealing with - but should use the resources at their disposal, including the Hot Dip Galvanizing Association and the galvanizer.
For example, before buying steel, the small business should ask the galvanizer for their recommendations and referrals to reputable steel merchants, and request certificates for any steel that is bought.”
Ambassadors for galvanizing
“We would really like to see the education, training and advisory requirements of micro-enterprises more adequately catered to by established industry,” Botha emphasises.
The good news on the galvanizing front is that this is already happening, with galvanizers that are members of the HDGASA setting up remote depots specifically to accommodate the needs of micro-enterprises.
Many HDGASA member galvanizers provide for depots in remote areas where articles for galvanizing can be dropped off and collected. Access to galvanizing is therefore closer than if it was only available at the galvanizers’ main facilities,” he explains.
“A strong relationship with a galvanizer gives the micro-entrepreneur opportunities over time. For example, the better the relationship, the better the quality of the products coming in, the welding and the preparation for hot dip galvanizing. Ultimately, this is about growing both businesses. The solo micro-entrepreneur who starts out making one gate, could be making 20 by the end of the year,” concludes Botha

02/09/2025

The essential pillars of corrosion control are built on steel value chain collaboration,
co-ordination and communication, says the HDGASA

Duplex coating - combining hot dip galvanizing with painting - is an extremely effective method of corrosion control.
“Paint on hot dip galvanizing is an excellent system, but it does require that everyone in the value chain understands the requirements for best practice,” says Robin Clarke, Executive Director of the Hot Dip Galvanizers Association of Southern Africa (HDGASA).
Several award-winning projects demonstrate its efficacy. These include the Kirstenbosch Gardens walkway - the steel work on the Cape Town soccer stadium - and the Standard Bank facade in Maputo. All required high levels of corrosion control, as well as architectural synergy with their surroundings.
Grappling with technicalities
The HDGASA frequently assists designers, architects, fabricators, galvanizers and paint professionals regarding the best approach to take to the duplex coating process - and its website includes useful documentation and methodologies to guide them.
For example, Clarke explains that a structure may require a paint over-coating to prolong service life in harsh marine and agricultural locations, exceptionally high pollution areas and corrosive micro-environments within processing plants.
However, both aesthetic and legislative requirements may play a role: “These might relate to a specific aesthetic to complement the surroundings - or a legislative requirement such as colour coding of pipelines, or meeting Civil Aviation Authority (CAA) requirements with regard to high-rise structures in and around airports or flight paths,” he advises.
Tried and tested corrosion control
Clarke describes hot dip galvanizing as a well-established, tried and tested, preferred corrosion control method. Extensive research between the 1940s and 1960s on hot houses in the Netherlands produced a very repeatable outcome when it came to service life. The same applied to certain paint systems. These were put onto the same galvanizing base as a third leg of the experiment - and the outcome was that the lifetime of the coating exceeded the sum of the two individual parts by at least 1.5 times in aggressive environments and up to 2.8 times in less corrosive situations.
Clarke explains that laboratory tests also determined that when paint became porous, the zinc from the galvanizing process plugged and sealed the micro-porosities, giving new life to the coating.
Another benefit is avoiding under-creep on a paint system: “If the paint is penetrated, the steel can rust under the paint. That does not occur when you have painted onto a galvanized or zinc-based coating. The zinc will sacrifice itself to restore the coating and, if it cannot, it will sacrifice itself to protect the carbon steel substrate.”
Collaboration and co-ordination to mitigate corrosion
Once duplex technology has been specified, important decisions around steel selection and preparation follow.
The HDGASA frequently advises about the best corrosion control approach in extreme environments, specifying silicon-controlled steel in terms of the SANS 1471 (parts 1 and 2) guidelines.
“The best manufacturing practice starts with ensuring that you select the most appropriate steel - which is silicon-controlled steel - and ensure the consistency of your steel supply throughout the project. If this is a substantial project that requires various steel suppliers, it will be very difficult to deliver the same paint aesthetic,” Clarke observes.
Clarke adds that, in terms of SANS 14713 for best manufacturing practices, the design must ensure an even flow of cleaning materials across the steel articles, address best practices in terms of welding, control of de-fluxing and anti-spatter. Safety is also paramount in the case of enclosed containers, where venting and filling holes need to be placed appropriately.
Communicating to achieve the perfect outcome
Clarke says the HDGASA recommends commencing with a gentle sweep blast of air to remove any products of oxidation, remnants or contaminants on the surface.
“We advocate very strongly that the paint manufacturer makes a recommendation in accordance with the ISO 12944 standards, which relate to a variety of painting systems that will be effective depending on the coating durability required for the project,” he says.
He also emphasises that the paint coatings for a single project should come from the same manufacturer to avoid incompatible paint.
“The engineer, the architect/designer and fabricator must inform the galvanizer that the material is to be over-coated or painted before the galvanizing process starts. At that point, the galvanizer and the painter will also need to liaise regarding the requirements for post-galvanizing surface preparation.”
“The painter will have looked at the HDGASA’s codes of practice and prepared the surface before following the manufacturer's recommendations to ensure that the paint is correctly mixed, applied and cured.
Therefore, adherence to the methodology of collaboration, co-operation and communication will ensure that the client ultimately receives a hot dip galvanized and painted article that - instead of lasting under ten years, will have a service life of double that,” Clarke concludes.

28/08/2025

“Bad Medicine for the Steel Industry?”
XA Global’s latest blog post delivers a sharp and timely critique of ITAC’s proposed steel tariffs, framing them as a potentially damaging intervention in an already fragile industry. The piece opens with a striking observation: one steel importer stands to see their duty liability spike by R119 million the moment the tariffs take effect. That figure alone sets the tone for what follows, a sobering analysis of policy, ideology, and unintended consequences.
CEO, Donald Mackay, situates the tariff proposal within a broader global trend toward localisation, drawing parallels to the Trump-era mantra of “importing is bad, local manufacturing is good, exporting is best.” It’s a worldview that casts trade decisions in moral terms, where buying local becomes a patriotic act and importing a kind of economic betrayal. In theory, localisation promises jobs, growth, and self-sufficiency. But XA Global urges readers to look beyond the rhetoric.
The real problem, they argue, is structural and global. China’s relentless overproduction has flooded steel markets worldwide, and even with R2 billion in support and aggressive protectionist measures, ArcelorMittal South Africa is teetering. The rise of subsidised mini-mills, producing steel from scrap, only adds to the glut, squeezing traditional producers further. The author’s metaphor is biting: this is “a crisis wrapped in a bubble inside a policy failure,” and tariffs, they suggest, are not the cure but a dose of “Bad Medicine.”
Even the potential upside, R6 billion in duties collected, comes with caveats. The author is sceptical that this will meaningfully shift demand to local suppliers. Tariffs, by design, reduce competition and raise prices. And when prices rise, consumption tends to fall. What’s especially troubling is the structure of the proposed duties: 77% apply to intermediate goods, 14% to capital goods, and just 9% to final consumer products. That means the pressure lands squarely on the upstream inputs that feed downstream industries, where 90% of steel-related jobs reside.
Steel is everywhere, from paperclips to pipelines, and making it more expensive has ripple effects across the economy. XA Global acknowledges ITAC’s difficult role in balancing competing interests across a complex value chain. Rebates exist, but they’re conditional, often costly to access, and subject to shifting regulatory requirements. They’re not a panacea.
Perhaps the most damning insight comes at the end: of the 819 companies that imported over R10 million worth of affected products, only 101 responded to ITAC’s investigation. The silence is deafening. Whether due to complacency, confusion, or misplaced faith in industry bodies, the lack of engagement has left ITAC with a narrow evidence base. As the author warns, “If you don’t speak up, how can you expect ITAC to hear your words?”
The blog doesn’t claim to have all the answers, but it does pose a critical question: is this truly “Bad Medicine,” or did the industry bring it upon itself by failing to act? Either way, the implications are profound.

Hot Dip Galvanizers Association Southern Africa

05/11/2025

03/11/2025

02/09/2025

02/09/2025

28/08/2025

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Monday	08:00 - 16:30
Tuesday	08:00 - 16:30
Wednesday	08:00 - 16:30
Thursday	08:00 - 16:30
Friday	08:00 - 15:00