We did our M30T's first annual condition inspection and my IA noticed that the prop screws had white oxidation on the screws and under the metal prop cover. After he looked closer, he stated that the steel screws had alminum oxidation on them due to the mix matched metals touching them.

When I posted my findings, there were members of the group that were giving S#1T, stating that it was just dried locktite, which I find hard to believe since this was all the way to the top and under the cap cover.

So, is it oxidation or loctite?

If it is oxidation, there could be a prop failure in the future for someone out there that hasn't done a close inspection.
BTW, the drone has not been flown in rainy weather, tho, it has flown in the winter doing SAR work.

I'd say : the blue-ish is the loctite, the white...something else but it should be replaced ( the screws are coated not sure / never saw it could create aluminium corrosion ). We send our units every year back for maintenance at DJI.

Thank you, yes, that is what we noticed. We know what Locktite is, but the white is the oxidation from the aluminum propeller post. and it was coated around the outside of the post and on the plastic opening and bushing on all eight props.

Dissimilar metals -> galvanic or bimetallic corrosion. Loctite is blue (you can even see a fine strand of it where it has peeled away from the threads on one of the screws). White crust is the oxidized aluminum into which the fasteners were threaded. Your diagnosis is spot-on.

https://en.wikipedia.org/wiki/Galvanic_corrosion

Can you link the original thread where people called that white crud "dried locktite"? I could use a laugh.

patiam Posted at 5-25 10:34
Dissimilar metals -> galvanic or bimetallic corrosion. Loctite is blue (you can even see a fine strand of it where it has peeled away from the threads on one of the screws). White crust is the oxidized aluminum into which the fasteners were threaded. Your diagnosis is spot-on.

https://en.wikipedia.org/wiki/Galvanic_corrosion

Thank you. Like I said, my IA confirmed that during the inspection. The post was on the DJI M30T Only Facebook forum (https://www.facebook.com/groups/731220487965144) , or  .. let's host trolls division!

After being told  "My ignorance was showing" I did the mature thing,  deleted the post and wish them well with their drones.  LOL

HD Pilot Posted at 5-25 14:24
Thank you. Like I said, my IA confirmed that during the inspection. The post was on the DJI M30T Only Facebook forum (https://www.facebook.com/groups/731220487965144) , or  .. let's host trolls division!

After being told  "My ignorance was showing" I did the mature thing,  deleted the post and wish them well with their drones.  LOL

Lol OK, Facebook, 'Nuff said. Thanks for clarifying.

In any event I was just agreeing w/ you and your IA. You posed the question in your thread title and subsequent posts, and I offered my opinion.

I think we could all benefit from hearing how you get on w/ DJI support regarding this issue if you take it up with them. Please share if so.

patiam Posted at 5-25 16:37
Lol OK, Facebook, 'Nuff said. Thanks for clarifying.

In any event I was just agreeing w/ you and your IA. You posed the question in your thread title and subsequent posts, and I offered my opinion.

I will gladly share if I hear anything from them, but I doubt I will even bring this up with support. My track record with support and correcting issues with the M30T over the past year is of no interest or consequence with DJI.

I have not purchased another Enterprise level drone from them since the DJI - Autel price slash. And the fact that DJI seems to have no interested in correcting or improving the software for the M30T since the release of the M3DT last October. IMO, the M30 and M30T is at EOL

Agreed. The M30 has always been a red-headed stepchild "Enterprise" platform, like the P4M and M2E... Hyped but half-baked and poorly supported.

patiam Posted at 5-25 20:37
Agreed. The M30 has always been a red-headed stepchild "Enterprise" platform, like the P4M and M2E... Hyped but half-baked and poorly supported.

Which is a shame. I do like the drone, it just needed the attention to keep it competitive. But when Autel copied the M30 and then offered it for $4K less, DJI showed their hand on the margin. I bought mine six weeks before they slashed the price and after I expressed a concern with any upcoming sales and discounts and was opening lied to by DJI sales and support about the stability of the price since the drone was relatively new to the market (about 7 months).
I'll get off my soap box while others laugh at my naivety.

HD Pilot Posted at 5-25 06:06
Thank you, yes, that is what we noticed. We know what Locktite is, but the white is the oxidation from the aluminum propeller post. and it was coated around the outside of the post and on the plastic opening and bushing on all eight props.

For the pleasure of discussion : Could it be the plastic vibrating and "breaking off"?

On the M300, at the arms there is also some white stuff but it's the carbon arm/plastic rubbing...at least it's what we supposed :-)

AR_AirPrecision Posted at 5-26 07:28
For the pleasure of discussion : Could it be the plastic vibrating and "breaking off"?

On the M300, at the arms there is also some white stuff but it's the carbon arm/plastic rubbing...at least it's what we supposed :-)

No, it was identified as galvanic corrosion by my IA and 2 A&P's  (aluminum oxidation). Similar to this photo of galvanic corrosion on a  steel plate.   Also, remember, the steel screws are screwed into the aluminum prop shaft post.

HD Pilot Posted at 5-26 07:52
No, it was identified as galvanic corrosion by my IA and 2 A&P's  (aluminum oxidation). Similar to this photo of galvanic corrosion on a  steel plate.   Also, remember, the steel screws are screwed into the aluminum prop shaft post.

[view_image]

Do you have an idea how long it took to corrode like that on your unit?

It is not impossible that the white residue is threadlocker which has dried. Loctite 222 does this.
To find out, it's very simple, you immerse the screws in acetone*. If it disappears it's thread lock, if it stays it's corrosion.

Then if it is corrosion you can collect it by scraping it, expose the collected residue to a flame, depending on the color you will know who is oxidizing what.

*I assume you are an adult but in case that is not the case take your precautions with acetone and flame.

AR_AirPrecision Posted at 5-27 09:23
Do you have an idea how long it took to corrode like that on your unit?

The M30T was bought new last May, but who knows how long it was sitting in China before I received it.

LV_Forestry Posted at 5-27 09:41
It is not impossible that the white residue is threadlocker which has dried. Loctite 222 does this.
To find out, it's very simple, you immerse the screws in acetone*. If it disappears it's thread lock, if it stays it's corrosion.

Would dried threadlocker migrate up the full length of the machine screw and under the top cap?

LV_Forestry Posted at 5-27 09:41
It is not impossible that the white residue is threadlocker which has dried. Loctite 222 does this.
To find out, it's very simple, you immerse the screws in acetone*. If it disappears it's thread lock, if it stays it's corrosion.

Well, here is a photo of the screws in acetone. Most of the oxidation fell off and you can see the residue on the bottom. It did not dissolve. The hard caked on residue is still on the a few of the screws.

HD Pilot Posted at 5-27 16:50
Would dried threadlocker migrate up the full length of the machine screw and under the top cap?

Yes, that's what happens when there are too many.

HD Pilot Posted at 5-27 16:59
Well, here is a photo of the screws in acetone. Most of the oxidation fell off and you can see the residue on the bottom. It did not dissolve. The hard caked on residue is still on the a few of the screws.

[view_image]

Seeing how it comes off I rule out corrosion.   This looks a lot like a threadlocker.  Put the residue in a flame, you will see if it is a polymer or an oxide.

LV_Forestry Posted at 5-27 20:49
Seeing how it comes off I rule out corrosion.   This looks a lot like a threadlocker.  Put the residue in a flame, you will see if it is a polymer or an oxide.

After drying the residue and scraped off the remaining material, it didn't burn, just discolored. Notice, that the blue locktite is still on the screws, and the preplacement screws had the same amount of locktite on the end as these do.

Later, I tried to burn the material off of a screw, it too discolored. after cooling I ran the screw under some water, the color return to a off white.

HD Pilot Posted at 5-27 20:57
After drying the residue and scraped off the remaining material, it didn't burn, just discolored. Notice, that the blue locktite is still on the screws, and the preplacement screws had the same amount of locktite on the end as these do.

Later, I tried to burn the material off of a screw, it too discolored. after cooling I ran the screw under some water, the color return to a off white.

So it can be corrosion. It doesn't seem very serious, by which I mean that the integrity of the screws is not affected.

LV_Forestry Posted at 5-28 06:10
So it can be corrosion. It doesn't seem very serious, by which I mean that the integrity of the screws is not affected.

it's not the screws that have corroded, it is the aluminum into which they were threaded. that's what goes 1st in these situations. so the female threads may be compromised.

@HD Pilot, got any macro pix of the threaded holes in the aluminum propeller posts?

patiam Posted at 5-28 12:03
it's not the screws that have corroded, it is the aluminum into which they were threaded. that's what goes 1st in these situations. so the female threads may be compromised.

@HD Pilot, got any macro pix of the threaded holes in the aluminum propeller posts?

Yes Pat thank you for the chemical clarification.  

I still remain skeptical because in the photo in the acetone bath the white parts seem to come off.  The flame test was inconclusive but I doubt it was done correctly.  

Last solution is to immerse the white residue in nitric acid.  If it is aluminum oxide it should completely disappear very quickly.  

Blue threadlocker is not the same thing as Loctite 222 for example, I don't know its properties so it may not react very quickly with acetone. But once again, regarding how white part comes off in acetone, it looks a lot like a bonding components.

I submit that the white crud would have come off in water just as well as it did in acetone- it isn't strongly adhered to the screws and simply rinsed off.

I love all the chemical tests to figure out what's going on here but to me the real diagnostic is whether the aluminum threads show signs of material loss. If the white stuff is Al2O3, it had to come from there.If there is no appreciable damage to the threads, this is all kind of moot, other than as a  puzzle.

patiam Posted at 5-28 14:34
I submit that the white crud would have come off in water just as well as it did in acetone- it isn't strongly adhered to the screws and simply rinsed off.

I love all the chemical tests to figure out what's going on here but to me the real diagnostic is whether the aluminum threads show signs of material loss. If the white stuff is Al2O3, it had to come from there.If there is no appreciable damage to the threads, this is all kind of moot, other than as a  puzzle.

I agree, much of it could have been broken up when I was taking off the screws, which was harder to remove than I have had with other DJI drones (thou they were the Mini's). Still, the residue didn't dissolve. As for the threads in the Prop post, the condition seems that they just had power on the surface, but the threads were still there.

Do either of you have a M30T?

If you do, when was the last time the props were removed to have the motors and prop mounts inspected?

HD Pilot Posted at 5-28 14:58
Do either of you have a M30T?

If you do, when was the last time the props were removed to have the motors and prop mounts inspected?

I don't have an M30 available, but I checked on the propellers of an M300:



What I notice is that the material comes off very easily, and that it does not dissolve, neither in nitric acid, nor in the nitric + hydrochloric acid mixture. 100% sure it's not aluminum oxide. I did the test with aluminum oxide recovered from a piece of aluminum that had been lying around in a greenhouse for years, it disappeared almost instantly on contact with the acid which becomes orange. On the pictures above, nothing happen.

What is above is valid for my case only, not necessarily for yours because the color is significantly different (Even if to the naked eye my residue appears whiter than in the photo so closer to yours) therefore it is impossible to say that it is the same thing only by photo.

LV_Forestry Posted at 5-29 07:19
I don't have an M30 available, but I checked on the propellers of an M300:
[view_image][view_image]
[view_image][view_image]

Could it be plastic/carbon?

AR_AirPrecision Posted at 5-29 23:44
Could it be plastic/carbon?

In my case it is certain that it is threadlocker since in the maintenance procedure either we replace with new screws having the product already installed (the blue part) or we can reuse the same screw if the imprint of the head  screw is not damaged but it is obligatory to use loctite 222.

In the case of the OP's M30 it would be necessary to know if the drone has already gone through a maintenance stage, in which case it could very well be probably it's threadlocker.  
If this is the first disassembly then in this case corrosion should be considered because obviously DJI only uses the pre-installed blue drop as locking means, which doesn't give this white residue.

Regarding another carbon/plastic material this is very unlikely because the screw is not in contact with any of these materials.

HD Pilot Posted at 5-28 14:58
Do either of you have a M30T?

If you do, when was the last time the props were removed to have the motors and prop mounts inspected?

Thanks for the thread description. Nope, I don't have an M30.