Can scratches in the clear coat be removed? Let's try polishing and repairing the gas tank

It is always a shock to find scratches on your beloved motorcycle's gas tank. However, in reality, many scratches caused by riding gear, tank bags, or keychains are often limited to just the clear coat layer on the surface of the paint. If the scratches are like that, there is a possibility that they can be made less noticeable or even completely removed by polishing with compounds or waterproof sandpaper. Here, we will introduce scratch removal techniques that even a Sunday mechanic can do, covering the basic structure of clear coat, how to identify scratches, repair methods using compounds and waterproof sandpaper, and precautions during work.

Gas tank scratches are more bothersome than you might imagine

乗降時やライディング時にウェアやシューズがガソリンタンクに擦れると、このような傷が付きがちだ。これらがクリア層だけの傷か、カラー層まで達しているかは、耐水ペーパーやコンパウンドで軽く擦ると分かる。

The gas tank of a motorcycle is located in the center of the body and is one of the exterior parts that the rider sees the most. Therefore, even small scratches can be surprisingly bothersome.

Common causes of scratches include contact with zippers, buckles, or shoe toes when getting on and off the bike, long-term rubbing from knee gripping, and friction from tank bag fixing belts or magnets. There are also cases where they are caused by contact with neighboring vehicles in parking lots while touring, or by wiping scratches during car washes.

While these scratches do not affect riding performance, once you start noticing them, they catch your eye every time you look at them. The mental damage is especially great for owners who cherish their vehicles.

However, if you correctly assess the condition of the scratches, it does not necessarily mean that repainting or replacing parts is required. First, it is important to check the depth of the scratches.

Motorcycle paint comes in types with and without a clear coat

To understand how to repair scratches, you first need to know the structure of the paint.

Many modern motorcycles use a "clear coat finish," where a color coat is applied over the base, and the surface is covered with a transparent clear coat. Whether it is a solid color or a metallic color, it is common to have a clear layer on top to enhance gloss and weather resistance.
The paint structure in this case is a three-layer structure:

・Base
↓
・Color layer
↓
・Clear layer

On the other hand, some older vehicles or certain parts omit the clear coat and use the color paint itself as the finished surface. Also, matte paint may use a special clear coat, and general polishing repairs may not be suitable.

The repair method introduced here is mainly for glossy clear-coated paint.

When checking the condition of the scratches, it is a good idea to first understand whether your vehicle has a clear coat.

If the scratch is only in the clear layer, it may be removed with compound

コンパウンドで傷消しを行う際は「細目」「極細目」といった名称の製品を使用する。これらは#1000より細かなペーパーの削り跡（ペーパー目）を消すことができる。

The first thing you want to try for scratch repair on a clear-coated vehicle is polishing with a compound.

Compound is a polishing agent containing abrasives that can smooth the paint surface while removing a very small amount of it.

If a scratch only enters the clear layer, it is like a groove on the surface of a transparent film. Therefore, by gradually leveling the surrounding area, the step becomes less noticeable, and as a result, the scratch appears to have disappeared.

First, wash the vehicle to completely remove sand and dust, and clean the painted surface. Then, apply a small amount of fine to ultra-fine compound to a cloth and gently polish around the scratch.

What is important here is to "start with the finest abrasive first."

If you suddenly use a coarse compound, you will cause new polishing scratches instead of removing the scratch.

The "fingernail check" is effective for determining the depth of the scratch. If it is a shallow scratch that your fingernail does not catch on, there is a high possibility that it is only damage to the clear layer, and it is often improved with compound.

As a simple method to judge the depth of the scratch along with the fingernail check, there is also the "water splash check."

When you splash water on the scratched area, if the scratch temporarily disappears or becomes less noticeable, it is highly likely that it is a shallow scratch only on the clear layer.

This is because the water fills the grooves of the scratch, suppressing the diffuse reflection of light and making the scratch harder to see. Conversely, if the appearance of the scratch hardly changes even when water is splashed, it may have reached the color layer or be a deep scratch.

Of course, you cannot make a complete judgment with this method alone, but if both conditions of "fingernail does not catch" and "scratch becomes less visible when water is splashed" are met, it is well worth trying a polishing repair with compound first.

If there is no change with compound, consider waterproof sandpaper

極細目耐水ペーパーの一例。これはシート状で専用スポンジに張り付けて使用するタイプのペーパーで、番手は2000番で非常に細かい。

ここでは#2000の耐水ペーパーでニーグリップ部分を擦ってみる。ペーパーをスポンジに張ることで、研磨時の圧力が均等になりムラが出づらいメリットがある。また研磨時にペーパーに水分を与えることで、削れたクリア層がペーパーに絡みづらくなる。

If the scratch does not become thinner even after using compound, there is a method of using waterproof sandpaper with higher abrasive power. For paint repair, ultra-fine grits from 1500 to 3000 are mainly used. For clear layer repair, it is common to start from around 2000 grit.

However, from here on, careful work is required because there is a risk of over-sanding.

When polished with waterproof sandpaper, the painted surface will temporarily become a whitish matte state. However, this is proof that the clear layer has been sanded and is not abnormal.

After that, polishing with compound will restore transparency and gloss.

Note that if you press the paper directly with your fingertips, pressure will concentrate and polishing unevenness will easily occur. Try to wrap the paper around a sponge or polishing block and polish evenly with the surface.

Many failures in scratch repair are caused by over-sanding from the beginning.

If you use coarse paper or powerful compound because you want to remove the scratch quickly, you may create polishing scratches larger than the original scratch.

The basics of paint repair are in this order:

For example, proceed in stages like:

・Ultra-fine compound
・Fine compound
・2000 grit waterproof sandpaper
・1500 grit waterproof sandpaper

The clear layer of the gas tank is not infinitely thick. If you sand too much once, it may reach the color layer, and repainting may be necessary.

In repair work, "watching the situation" is a shortcut to success rather than "attacking."

If you have a polisher, you can save time and polish evenly

ポリッシャーで磨きたい部分にコンパウンドを適量塗布する。塗りすぎるとバフの回転力で周囲に飛び散ってしまうので、コンパウンドをバフに塗ってから磨いても良い。

マイクロファイバークロスによる手磨きでも充分だが、ポリッシャーを使用することで磨きムラが出ず作業時間短縮にも役立つ。ポリッシャーをタンクに押しつけるとコンパウンドの研削力を引き出すことができるが、強く押し当てると深い磨き傷が入ることもあるので注意しよう。

ポリッシャーで磨いた後は古タオルや古Ｔシャツなど硬い布ではなく、残ったコンパウンドはマイクロファイバークロスで拭き取る。

For small scratches, hand polishing with a microfiber cloth is sufficient. However, if there is a wide range of rubbing or if multiple compound operations are required, having a polisher will significantly improve work efficiency.

A polisher is a tool that performs polishing by rotation or vibration, and it is characterized by being able to polish with more uniform force than human hands.

Especially for parts with many curved surfaces like a gas tank, it is less likely to have uneven finish than hand polishing using a polishing block, and work time can be shortened.

In recent years, small cordless models for DIY have been increasing, and if you have a hobby of maintaining cars and motorcycles, it is convenient to have one.

However, because the abrasive power is high, it is forbidden to continue polishing the same place for a long time. Even when using a polisher, the work procedure of starting with an ultra-fine compound does not change.

If it has not reached the color layer, try polishing repair

「仕方ない」と諦めていた傷が再塗装なしでリフレッシュできるのが磨き作業の魅力だ。目の前の傷がクリア層だけで留まっているのかカラー層に達しているのかを判断した上で、クリア層の傷ならコンパウンドや耐水ペーパーで磨いてみよう。

When you see scratches on the gas tank, you tend to think, "It won't be fixed unless I repaint it." However, in reality, many scratches from riding gear and tank bags are limited to the clear layer.

If your fingernail does not catch on the scratch, or if it becomes less visible when you splash water on it, it is worth trying a repair with compound first. If it still does not improve, use ultra-fine waterproof sandpaper in combination, and proceed with the work while carefully checking the condition.

What is important is not to perform strong polishing suddenly. Both compound and waterproof sandpaper should be started from a fine grit, and by watching the situation little by little, you can significantly reduce the risk of failure.

If the scratch has not reached the color layer or the base, it is not rare for it to become surprisingly clean without painting. If you find a bothersome scratch on your beloved tank, why not try polishing repair first?