{"id":66333,"date":"2026-07-25T08:00:11","date_gmt":"2026-07-24T23:00:11","guid":{"rendered":"https:\/\/norimen.net\/?p=66333"},"modified":"2026-07-22T18:49:17","modified_gmt":"2026-07-22T09:49:17","slug":"no-anti-rust-oil-required-for-the-rebar-insertion-head","status":"publish","type":"post","link":"https:\/\/norimen.net\/en\/rebar-insertion-head-anti-rust-oil-unnecessary\/","title":{"rendered":"Is Anti-Rust Oil for Rebar Insertion Tools Really Necessary? | Galvanized HDZT77 and the Limit of Oxidation Degradation"},"content":{"rendered":"

Hello, everyone.<\/p>\n

This is Enta.<\/p>\n

It's been hot every day, huh? lol<\/p>\n

It's been like a steam room out here since this morning, and it feels like my stamina is going to wear out first.<\/p>\n

Let's make sure to stay well-hydrated and get enough salt ^^<\/p>\n

\n

But that's beside the point.<\/p>\n

This time, we\u2019ll be discussing the question: \u201cIs anti-rust oil really necessary for the heads of rebar inserts?\u201d<\/p>\n

I've written quite a bit in the past about questions and issues regarding oil caps.<\/p>\n

Today, I\u2019ll revisit this topic using figures on the service life of galvanized steel and the lifespan of rust-preventive oil.<\/p>\n

\n

Do you know the limit of oil oxidation and degradation?<\/h2>\n

Have you ever heard of the \u201coxidation degradation limit\u201d for oil?<\/p>\n

Rust-preventive oil is a type of oil designed to protect metal surfaces from moisture, air, and dust, thereby preventing rust.<\/p>\n

However, the oil itself doesn't last forever.<\/p>\n

From what I've noticed, if you leave rust-preventive oil as is, it starts to turn blackish within about a week.<\/p>\n

I think most admins probably know this from experience, lol (the pails of rust-preventative oil we used, lol).<\/p>\n

The photo below shows the oxidative degradation of rust-preventive oil arranged in a color gradient.<\/p>\n

\"Oil<\/p>\n

Depending on the conditions, after about five years in your hair, the color tends to fade quite a bit, doesn't it?<\/p>\n

To begin with, each type of rust-preventive oil has a recommended duration of rust protection.<\/p>\n

Anti-rust oils are classified by JIS standards and are categorized from NP-0 to NP-20 based on film properties and base oil; it is generally considered that the thicker the film, the longer the rust protection period.<\/p>\n

In other words, it is not a material that guarantees \u201cunconditional, lifelong protection\u201d simply by applying rust-preventive oil; rather, it is a consumable whose lifespan varies depending on the type, film thickness, and environmental conditions.<\/p>\n

 <\/p>\n

It is said that the reason iron rusts in the first place is that oxygen and moisture combine, causing the iron to try to return to its natural, stable state as iron oxide.<\/p>\n

Rust-preventive oil prevents rust by blocking oxygen and moisture from reaching the metal surface.<\/p>\n

However, as the oil itself reacts with oxygen, heat, and dust and gradually oxidizes, this protective effect also gradually diminishes.<\/p>\n

Some products, like volatile types, lose their active ingredients over time. (Like Kure 556, for example.)<\/p>\n

That\u2019s why I think it\u2019s closer to reality to think of it not as \u201cit\u2019s over once it\u2019s in,\u201d but rather as \u201cthe countdown starts the moment it goes in.\u201d<\/p>\n

It is said that the effective lifespan of anti-rust oil applied to the head is about five years at most (KJS Ground Anchor Association).<\/p>\n

After all, they're exposed to the blazing summer heat, and in the worst-case scenario, they're actually melting, right...<\/p>\n

Oxidation progresses rapidly with heat.<\/p>\n

 <\/p>\n

According to a survey we conducted previously, 62% of respondents said they didn't need it.<\/p>\n

\"Presence<\/p>\n

By the way, there's a survey button on the left side of this site.<\/p>\n

We also conducted a survey in the past titled \u201cIs rust-preventive oil necessary for rebar installers?\u201d so if you\u2019re curious about the results, feel free to check that out too lol.<\/p>\n

\n

Even among anchors, which are the most demanding when it comes to rust prevention, the approach to the head has changed.<\/h2>\n

Now, let's talk about ground anchor construction.<\/p>\n

Among slope stabilization methods, ground anchors are the type that requires the most rigorous rust and corrosion prevention measures.<\/p>\n

The reason is that PC steel, which is subjected to high tensile stress in the tendons, poses a risk of stress corrosion cracking or fracture as corrosion progresses.<\/p>\n

For this reason, the Design and Construction Standards for Ground Anchors (JGS4101-2012, Japanese Geotechnical Society) also require reliable corrosion protection (Corrosion Protection Class II or higher) for anchors with a service life of two years or more.<\/p>\n

The standard clearly states that special care must be taken because insufficient corrosion protection from the head to the tension section may result in fracture due to corrosion.<\/p>\n

In particular, boundary areas\u2014such as the back of the fastener or the connection point with the tension member\u2014are prone to discontinuities in the corrosion-resistant structure, making them the areas most susceptible to corrosion.<\/p>\n

That just goes to show how much Anchor cares about rust prevention around the head.<\/p>\n

\"Clear
KJS Ground Anchor, Clear Cap, Grease-Free<\/figcaption><\/figure>\n

As a method for protecting the anchor head from corrosion, the standard document (Guidelines for the Design and Construction of Ground Anchor Works) states that \u201cit is common practice to cover the head with a corrosion-resistant cap and fill the cap with a corrosion-preventive material, such as anti-rust oil.\u201d<\/p>\n

At this point, you might be thinking, \u201cSo Anchor uses rust-preventive oil after all,\u201d but what I\u2019m really focusing on is what comes next.<\/p>\n

The same standard also states that the protective material filled into the head section \u201cmust be constructed of materials and designed in such a way that it does not leak, evaporate, or settle, and must be designed so that it can be replenished later.\u201d<\/p>\n

In other words, the manual itself is based on the assumption that the rust-preventive oil added will eventually evaporate or settle, and therefore anticipates that it will need to be replenished later.<\/p>\n

In short, this means that the anti-rust oil for the head isn't treated as a \"material that stays effective indefinitely once applied,\" right?<\/p>\n

And recently, there has been a growing trend\u2014albeit a modest one\u2014suggesting that it might be better not to apply anti-rust oil to the anchor head.<\/p>\n

Even the anchor heads\u2014which are the most sensitive when it comes to rust prevention\u2014are like that, so how much longer are rebar installers going to keep using rust-preventive oil on the heads? That\u2019s the question I\u2019m raising this time lol (How many times am I going to say this? lol)<\/p>\n

\"Oil<\/p>\n

\n

The rebar used in rebar insertion work is HDZT77 galvanized and will not rust for 50 to 100 years.<\/h2>\n

How is corrosion protection handled on the rebar insertion (rock bolt) side?<\/p>\n

Unless temporary structures require the use of bare (ungalvanized) rebar, hot-dip galvanized rebar is the standard for rebar installation work.<\/p>\n

The amount of residue is oftenHDZT77<\/strong>is specified.<\/p>\n

This is a classification under JIS H 8641 (hot-dip galvanizing) and corresponds to the former HDZ55 prior to the revision; in terms of zinc coating weight,550 g\/m\u00b2 or more<\/strong>, in terms of film thickness,77 \u00b5m or more<\/strong>This is the class.<\/p>\n

This is one of the highest-grade specifications for galvanized coatings, originally designed for use in \"harsh corrosive environments.\"<\/p>\n

So, how long will it last at this level of adhesion?<\/p>\n

The service life of hot-dip galvanizing can be estimated using the following formula, based on atmospheric exposure test data from the Japan Hot-Dip Galvanizing Association.<\/p>\n

Service Life = Zinc Deposition Rate \u00f7 Corrosion Rate \u00d7 0.9<\/p>\n

 <\/p>\n

This formula is based on the assumption that rust begins to form on the base metal when approximately 10% of the zinc coating remains (according to the explanatory notes for JIS H 8641).<\/p>\n

If we substitute the coating weight of 550 g\/m\u00b2 and the zinc corrosion rates for each environment into this formula, the results, based on the association\u2019s data, are roughly as follows.<\/p>\n

\"Plating:
Japan Hot-Dip Galvanizing Association (General Incorporated Association)<\/figcaption><\/figure>\n

In rural areas, the corrosion rate is low, and the service life is approximately110 years<\/strong>\u3002<\/p>\n

Even in urban and industrial areas, approximately53<\/strong>\u3002<\/p>\n

Even in coastal areas, approximately45 years<\/strong>\u3002<\/p>\n

Many of the mountainous slope sites we work on are located in areas that resemble rural landscapes.<\/p>\n

When you think about it that way, with HDZT77 galvanized rebar, depending on the conditions,For nearly 100 years<\/strong>This calculation will never go wrong.<\/p>\n

Even by a strict standard, as long as it's not raw material, at the very least50 years<\/strong>The numbers show that it's on the firm side.<\/p>\n

Incidentally, for large structures such as bridges, the thickness of the material means that the coating weight ranges from about 800 to 2,000 g\/m\u00b2, and their service life is considered to be virtually indefinite.<\/p>\n

It is also said that, indoors, it lasts more than five times as long as it does outdoors in the same area.<\/p>\n

Although the head of a rebar inserter is exposed to the outdoors, it doesn\u2019t reach that level of exposure; even so, a coating of the HDZT77 class is capable of withstanding rust for several decades.<\/p>\n

I made a simulator, so please give it a try lol<\/p>\n