White crystals forming around the spokes - corrosion?

[Ali-bear]

I haven't used the GS for weeks now since the first time it was cold enough for a risk of ice on the road. I left it in the garage, filthy from the last time I did manage to ride, and I didn't have the opportunity to clean it until last weekend because it has been freezing all the time. There shouldn't be any salt on the bike because I stopped riding when the gritters came out, so I thought leaving it dirty was better than washing it and leaving it covered in ice!

The rear wheel looked like it had snow crystals around the spokes where they meet the rim. Front wheel was OK. Some white, more powdery deposits around some of the bolts on the front of the engine casing. I suppose its corrosion? The famous galvanic corrosion or whatever its called where different metals meet? Blimey these GS's rust easily!

It was slightly above freezing last weekend so in desperation I washed the GS. Would have used a pressure washer (at a safe distance) on the wheel rims but it was frozen and didn't work... I used BMW wheel cleaner which got rid of the white stuff but there is still a deposit on the rim, around the spokes and spots around in other places. Its dark grey/black and extremely hard. Brake dust? There is a small amount of the same deposit on the front wheel but nowhere near as much. I would have thought the wheel cleaner would remove brake dust though. Any ideas what it is and how I get rid of it?

Could be a sign that your bike has been abusing drugs.

 

[theop]

actually it doesn't.

personally used hot water for decades with no instance of accelerated corrosion. hot water shifts the salt off the bike better IMO.

actually it does (cookie clearly not a scientist).... Temperature matters. Not the primary reason, but let me explain:

The main cause of corrosion is water with a low pH. Fact. Acidic waters have lots of H+ ions in the water to react with the electrons at the cathode, so corrosion is enhanced. In contrast, water with a higher pH (basic water) lowers the solubility of calcium carbonate so that the calcium carbonate is more likely to precipitate out as scale.

Other chemicals and compounds found in water also influence the corrosion process. The most common of these are oxygen, carbon dioxide, and dissolved solids.

Oxygen reacts with hydrogen gas at the cathode, causing depolarization and speeding up the corrosion. As a result, water with a high D.O. (dissolved oxygen) will tend to be corrosive. Other oxidizing agents can perform the same function, although they are less common. Nitrates and chlorine are two other oxidizing agents found in water.

Carbon dioxide in water also tends to cause corrosion. The carbon dioxide gas can combine with water to form carbonic acid, which lowers the pH of the water and akes it more corrosive.

Dissolved solids are typically present in water as ions. These ions increase the electrical conductivity of the water, making the electrolyte more effective. Thus, they also increase the rate of corrosion.

In addition to the chemical properties of water, physical characteristics will influence corrosion. The most important of these physical characteristics are TEMPERATURE and velocity of flow.

Temperature speeds up the rate of corrosion just as it does most other reactions. However, the effect of temperature on corrosion can have positive effects, but is too complex for this forum. In pipes ans shipping vessels,a high water temperature reduces the solubility of calcium carbonate in water, which promotes scale formation and slows corrosion. This alleviating factor of temperature is rather irrelevant for the bikes. Temperature also alters the form of corrosion. Pits and tubercles tend to form in cold water while hot water promotes uniform corrosion, thus making it more visible in items like cars and bikes.

The influence of flow velocity on corrosion is also rather complex and more related to pipes, ships etc. The higher the fluid velocity, the higher the rate of corrosion.

Hope the above helps

 

[thornley]

actually it does (cookie clearly not a scientist).... Temperature matters. Not the primary reason, but let me explain:

The main cause of corrosion is water with a low pH. Fact. Acidic waters have lots of H+ ions in the water to react with the electrons at the cathode, so corrosion is enhanced. In contrast, water with a higher pH (basic water) lowers the solubility of calcium carbonate so that the calcium carbonate is more likely to precipitate out as scale.

Other chemicals and compounds found in water also influence the corrosion process. The most common of these are oxygen, carbon dioxide, and dissolved solids.

Oxygen reacts with hydrogen gas at the cathode, causing depolarization and speeding up the corrosion. As a result, water with a high D.O. (dissolved oxygen) will tend to be corrosive. Other oxidizing agents can perform the same function, although they are less common. Nitrates and chlorine are two other oxidizing agents found in water.

Carbon dioxide in water also tends to cause corrosion. The carbon dioxide gas can combine with water to form carbonic acid, which lowers the pH of the water and akes it more corrosive.

Dissolved solids are typically present in water as ions. These ions increase the electrical conductivity of the water, making the electrolyte more effective. Thus, they also increase the rate of corrosion.

In addition to the chemical properties of water, physical characteristics will influence corrosion. The most important of these physical characteristics are TEMPERATURE and velocity of flow.

Temperature speeds up the rate of corrosion just as it does most other reactions. However, the effect of temperature on corrosion can have positive effects, but is too complex for this forum. In pipes ans shipping vessels,a high water temperature reduces the solubility of calcium carbonate in water, which promotes scale formation and slows corrosion. This alleviating factor of temperature is rather irrelevant for the bikes. Temperature also alters the form of corrosion. Pits and tubercles tend to form in cold water while hot water promotes uniform corrosion, thus making it more visible in items like cars and bikes.

The influence of flow velocity on corrosion is also rather complex and more related to pipes, ships etc. The higher the fluid velocity, the higher the rate of corrosion.

Hope the above helps

Thanks for that. There's at least two of us with an understanding of metalurgy

 

[(RIP) Kaister]

White crystals forming around the spokes - corrosion?

wtf do you think it is ?

cocaine ? baking powder ? , lithium disulphide, ? alien bat shit ?.


of course its feckin corrosion

 

[FatBob]

wtf do you think it is ?

cocaine ? baking powder ? , lithium disulphide, ? alien bat shit ?.


of course its feckin corrosion

Yeah, silly me. I thought that not actually riding on salted roads and leaving the bike in the garage would stop it corroding. I should have known better, its a BMW after all!