Corrosion and compatibility: the real test for Lubrizol

It had to go back to basics, its Global OEM Technical Manager for large engines, Lawrie Peck, told The Motorship, rather than base its development of existing formulations, such as those for use with low-sulphur fuels. “Because ammonia is so new, we’re back at the fundamental stages to understand how ammonia will affect the lubricant and the engine”, he said.

Harriet Brice, Lubrizol’s Technology Manager for marine diesel engine oils, pointed out a key difference between ammonia and current fuels, saying that “ammonia poses itself as a corrosive chemical” which has prompted “some basic experiments around introducing typical engine parts to ammonia environments”.

This involved exposing samples of metals found in marine engines to ammonia and revealed that “only steel is not impacted” by its corrosive nature, she reported.

Even getting this far was not straightforward. As Mr Peck explained, a risk assessment was carried out, “making sure we understand what hazards and risks are likely to occur when we’re using ammonia in the laboratory”. With that completed, “we’ve got a safe way of experimenting with ammonia and initial lubricant formulations [but] that takes a long period of time”.

It has resulted in new understandings about “how we manage ammonia and lubricant samples … which we will feed out to the OEMs and eventually operators of these engines”, he said.

As well as its effect of engine components, ammonia’s basicity might pose some new interaction chemistries with components in the lubricant, which would have to be considered in its preparation, Ms Brice said. She confirmed that Lubrizol is looking at the compatibility of various oil additives with ammonia but no information is publicly available about its findings.

Although final lube oil formulations are not yet available, this will not hinder OEMs as they develop their engines, Mr Peck believes, since their focus is on how best to introduce the fuel into their engine and how it will combust, so a basic modern lubricant will be sufficient for those purposes.

Nonetheless, its own development work – which has been going on for a couple of years – is affected by progress made by the OEMs. Once their engines reach design sign-off, “we will understand what conditions we need to fine tune the lubricant testing”. Until then, “there’s only so far we can go”, he said.

Lubrizol has not reached that point yet and is exploring some important aspects of ammonia use, such as its combustion. Unlike other fuels, it is basic when it is injected and produces acidic emission products so “we are covering all the scenarios of whether that basic ammonia will hang around longer than we think and how much of those acidic products might be formed”, Ms Brice said.

She spoke about the situation that can arise with sulphur-containing fuel, in which considerable amounts of sulphuric acid are produced that can condense and cause cold corrosion. With ammonia, “will there be a lot of nitric acids produced and will they have the same tendency to condense?” she wondered. Even if there is less acid than from sulphurous fuels, it will still need neutralising by a basic lubricant, she said.

A further complexity arises if a pilot fuel is needed for combustion. If so, “what will the pilot fuel be? And if that contains some sulphur, we’ll still need some BN to handle that”.

Mr Peck confirmed that because of ammonia’s unique combustion properties, there will be “quite a range of conflicting conditions within the engine”. So he described the fuel as “a new unknown” and said that there is no standard yet for marine-grade ammonia, so Lubrizol is using generally-available gaseous ammonia for its development work. This is not a new experience; the same situation arose when VLSFO was under development, he recalled; “it’s just something we have to be patient about”.

In the meantime, “we are working to understand ammonia” to create a balanced formulation that will be effective once engines using it go into operation.