Cleaning Gearbox Housings – Water, Not Sand

The problem with solid blasting media

Sandblasting looks like the quick fix for a crusted housing — for gearbox parts it is the wrong one. Solid media such as sand or corundum embed themselves in soft metals such as magnesium and aluminium. Whatever remains in oil galleries or bearing seats later acts like grinding paste in the running gearbox: here, residue decides bearing life.

Then there is the look: blasting with solid grit compacts and smooths the surface. A uniformly shiny magnesium housing is instantly spotted by connoisseurs as “restored too prettily” — originally these housings had a slightly mottled, matte appearance. And blasted housings oxidise again immediately without further treatment.

How we do it: water blasting

Water blasting is done in our own workshop — as the cleaning stage before any housing restoration, rebuild or surface finishing. The high-pressure water jet removes oil, dirt and loose deposits without any solid blasting medium.

Nothing is left behind
no grain in an oil gallery, no dust in a bearing seat — the part can be assembled or treated further without elaborate re-cleaning.
Gentle on soft metals
magnesium and aluminium housings keep their surface and their dimensions.
An honest assessment
only on the cleaned housing do cracks, worn threads and run-in bearing seats show — the inspection becomes reliable.

For the factory finish: magnesium pickling

For magnesium housings — such as those of 901 and 915 gearboxes — water blasting is followed by our speciality: magnesium pickling. Pickling is a chemical surface treatment without mechanical removal: it takes off oxide layers, reveals corrosion underneath and does not change dimensions — bearing seats and sealing faces remain untouched.

The result is not high gloss but the true, slightly mottled factory finish the gearbox once left the works with — a difference at concours judging. Plating, powder coating and painting are organised with proven partners; water blasting and pickling remain in-house as core skills.

The normal case: combined with a rebuild

Most often, housing cleaning runs as part of a gearbox rebuild: the gearbox is stripped, the housing water-blasted and pickled, every part inspected and reconditioned — the result is a gearbox that is technically and visually true to the works, finished with a test-bench run.

Common questions

01 Why not simply sandblast?

Solid media such as sand or corundum embed themselves in soft metals such as magnesium and aluminium. Residue in oil galleries or bearing seats later acts like grinding paste inside a running gearbox. Water leaves nothing behind that could destroy a bearing.

02 What is water blasting exactly?

The surface is cleaned with a high-pressure water jet. Oil, dirt and loose deposits are removed without any solid blasting medium — the part comes out clean, but neither roughened nor contaminated with grit.

03 Can I send in just the housing?

Yes. We accept housings for water blasting and pickling on their own — just like shafts, gear parts or limited-slip differentials. The process is explained step by step on our “Send in your gearbox” page.

04 Why does an original magnesium housing look mottled?

Magnesium reacts unevenly in air — even at the factory these housings had that slightly mottled, matte appearance. A uniformly shiny blasted housing is instantly spotted by connoisseurs as “restored too prettily”. Pickling restores exactly the original look.

What is on your bench?

Gearbox type and a few lines about your request — that is all we need for a first assessment. A photo helps but is not required. The answer comes from the machinist, not from sales.

Send inquiry

Reply usually within 24 hours — from the managing director himself, no ticket system, no call centre. We call back on request.

or directly: 06628 9159093 · info@antriebstechnik-schmidt.de