Corrosion

[pstephens46]

It's interesting why certain parts corrode or rust when other parts nearby do not.
This bracket for example. Mainly on the ends. I replaced the diaphragms on both low pressure fuel pumps on my F150. The bottom screws on both pumps were jammed with rust. The other four were fine.

[99yam40]

my thoughts are
more moisture/ salt collection there,
or protective coating not as good in those spots

[pstephens46]

Weird thing is that it is a vertical bracket.

[zenoahphobic]

The picture shows corrosion around the holes where other metal such as a bolt had been. This greater corrosion is because the metal composition between the plate and the bolt (or the fastened component) is different, setting up an electric field just like in a battery. If you place that bracket back but do not bolt some of the holes the corrosion will slow down at these places. Overtime the corrosion pattern will change.
It is interesting the part the water plays. For rust to occur at "room temperature" water is needed as an electrolyte, ions being able to move better within salt water than fresh. It is the conductivity of the water and not the amount of oxygen dissolved in the water. Salt water holds far less oxygen than fresh but iron rusts (the chemical combination with oxygen) quicker in it.

[pstephens46]

Curious as to why the two outer holes had far more than the other two. This bracket is attached to a mechanical throttle body. The screws, all 4, are stainless. The bracket is some electro zinc plated crap...

[TownsendsFJR1300]

Perhaps the coating was applied a bit light on that part. Do you have similar corrosion elsewhere (similar metal) on other parts?

I'd sand those spots to bare metal. Rustoleum has a "galvanize spray" (rattle can) that works really, really well... Couple coats and it'll last a long time...
(I used it on my steel lift extensions). I had to weld a tab to a new extension (ground down to bare metal) and I used that. It gets soaked in brackish/salt water whenever the boat is lowered... Been that way 10 years, NO RUST...

Plus one with 99 as well, once assembled, soak that power head with LPS or similar...

[zenoahphobic]

Maybe there is more dissimilar metal attached at these ends that forces the steel to "sacrifice " more. Being at the ends means there is less sacrificial metal there.
More likely those areas retain the moisture more, maybe don't retain enough engine heat to dry off.
You will probably scrap off and neutralise the rust and paint with a zinc rich paint. If you can get zinc washers you could also if worth the trouble add more galvanic protection there.

[pstephens46]

For now, naval jelly and a brass brush. Then soaked it in Boeshield.

Why? Because I have to look at the wretched thing every time I remove the cowl.

[99yam40]

I sure miss having access to a bead blaster and powder coating machine for things like this since I retired

[panasonic]

Perhaps the coating was applied a bit light on that part. Do you have similar corrosion elsewhere (similar metal) on other parts?

I'd sand those spots to bare metal. Rustoleum has a "galvanize spray" (rattle can) that works really, really well... Couple coats and it'll last a long time...
(I used it on my steel lift extensions). I had to weld a tab to a new extension (ground down to bare metal) and I used that. It gets soaked in brackish/salt water whenever the boat is lowered... Been that way 10 years, NO RUST...

Plus one with 99 as well, once assembled, soak that power head with LPS or similar...

Plus one Scott. Before the Galvanize spray I use this rust converter on the cleaned up areas...works very good.

[TownsendsFJR1300]

Yep, ^^^, those products work good...

And Pat, you can do a cover/final coat of silver or black and it'd look stock..


* I had powder coated a bracket I made (years back) to hold my "dock box" to a davit (now sold). The powder coat started rusting so I sanded all of that off and finished with the above product.

Final coat of Rustoleum shiny grey, lasted years (no rust) till I just sold them..




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[TownsendsFJR1300]

This bracket Pat?


I now gather your talking TWO different area's, (as the pumps are not near this /the bracket-at least on my engine)..


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