How to remove rust from metal?

Cleaning and protecting metal mechanical parts from rust is a common operation but also necessary in the industry to ensure the proper functioning of the parts and guarantee their durability. Many solutions using chemical and mechanical processes exist today to derust metal parts. However, in addition to being often time-consuming, they generate risks for: the health and safety of operators, damage to parts and the environment.

How does rust form?

Rust forms as a result of a so-called oxidation-reduction reaction, which is a slow chemical process involving the iron molecule (whether in pure iron or an iron-based alloy), present in the metal, exposed to air oxygen and water. It therefore intervenes when the metal is exposed to humidity for a long time.

Certain circumstances will also favor the appearance of rust, such as:

  • Different oxygen concentration conditions such as at sea, where the presence of salt water further accelerates the process
  • The presence of certain metals such as iron which is very easy to oxidize, unlike lead or stainless steel.

As soon as oxidation appears, it corrodes the metal, expands it and causes it to change its appearance. For example, copper turns orange then green on contact with oxidation. Then the oxidation will gradually spread, weakening the metal part until it punctures and crumbles.

Why remove rust from your metal parts?

The consequences of rust forming on metal parts are significant in all industries.

The embrittlement of mechanical parts due to rust can, under the pressure of production processes, reach their breaking point and cause stoppages in production lines or breakdowns in vehicles. This can lead to significant intervention costs, but also in terms of production losses, as well as leading to risky situations for the safety of operators.

The effects of rust thus lead to overconsumption of iron and steel production: more than 15% of steel production would serve only to replace parts damaged by rust, which can represent large sums for the company.

The consequences on the environment are also considerable in terms of the generation of waste from excessively damaged metal parts.

Implementing effective methods of rust removal as part of preventive maintenance along with protective coating can therefore help to ensure the durability of parts, saving money and saving new replacement purchases. expensive equipment.

remove rust from metal parts

How to effectively remove rust from metal?

A rustproofing process in industry always includes a process for cleaning mechanical parts and tools upstream, which are generally covered in grease and dust. The parts also require impeccable cleaning so that the adhesion of the protective coating takes place in the best conditions.

Removing rust from metal parts is a complicated task, especially when the surface of the part is not flat.

Fortunately, there are currently many solutions for derusting and degreasing metal parts:

  • some using chemicals such as phosphoric or hydrochloric acid baths
  • some of the multi-step mechanical processes such as sandblasting, shot-blasting or mechanical brushing followed by intense polishing of the parts
  • or other automated industrial cleaning machines such as ultrasonic tanks or immersion machines.

Chemical rust removal process

A chemical deoxidation process based on phosphoric acid, hydrochloric acid or caustic soda makes it easy to remove rust but presents many risks, both for the operators and for the parts.

These products will stop oxidation and remove rust but are highly corrosive and irritating to the skin, eyes, respiratory and digestive tracts if exposed. It is therefore necessary to consult the Safety Data Sheets (SDS) of these products before handling them as a precaution.

They are also dangerous for the environment, especially for the fauna and flora of aquatic environments because they increase the pH of waterways. They are also very aggressive on metal parts and risk damaging them, in particular for precision mechanics where these processes are to be banned. It is also mandatory to trace the end of life of these products according to the regulations.

Mechanical process to derust mechanical parts

remove rust from metal parts

The mechanical way using pickling techniques is the most common way to remove rust from mechanical parts, although they can be time consuming and often tedious for operators.

This includes sandblasting and shot-blasting, which consists of projecting jets of sand or high-pressure iron shot onto metal parts. These surface treatment operations expose operators to risks with the exposure of dust generated and dispersed in the air, which can cause respiratory tract disorders. High-pressure abrasive blasting can also cause severe pitting to appear on the surface of the metal and damage the more delicate parts of the components beyond repair.

There are also techniques using abrasive sandpaper or metal radial brushes but they cause traces of more or less deep grooves in the metal.

All these mechanical operations must often be followed by intensive polishing to achieve a satisfactory finish of the metal parts in order to be able to coat them with protection.

Process using industrial cleaning machines

Faster, simpler, more efficient, industrial cleaning machines can both clean grease and dust from your metal parts but also remove rust effectively.

For this, ultrasonic cleaners are the best solution for degreasing and completely eliminating rust while preserving metal parts, even their most fragile elements. Ultrasounds form pressure variations which propagate in materials immersed in a liquid. These high-frequency vibrations produce millions of tiny microscopic bubbles whose particularity is to immediately implode on contact with the part, releasing high energy which causes the oxides to detach even in inaccessible corners. At the same time, the implosion of these bubbles generates movements in the bath, conducive to cleaning. Thanks to fully automated cleaning cycles, operators can also concentrate on other key tasks.

Cleaning machines using immersion/agitation baths can also be used to remove rust, while keeping the parts intact and without operator intervention.

Upholstery and carpet cleaning with injection and extraction vacuum cleaners

Cleaning upholstery or carpets is usually a delicate task and we recommend always leaving it in the hands of professionals. Not using the right product and method on textile fibers depending on their nature or type of dirt can cause us to even permanently damage the surface. or colour.

Today we can find hundreds of dry cleaning products, foams and endless techniques and home methods on the internet, but in most cases it is necessary to clean with a wet system to clean and disinfect properly, we insist depending on the type of material.

We can find 2 processes to carry out wet cleaning professionally, a manual process indicated especially for synthetic upholstery or fabrics protected with anti-absorbent treatments and a mechanical process, in which we are going to delve a little deeper in this post, which has results. deep hygiene and disinfected and is indicated for upholstery and carpets with absorbent textile fibers.

To carry out this mechanical process of wet cleaning for upholstery and carpets, it is necessary to use professional machinery, in this case injection and extraction vacuum cleaners, capable of introducing or injecting cleaning and extra-disinfecting products into the fabrics or absorbing the same time dirt and dry the surface. Although it may seem like a process similar to using soapy water and a cloth, the result in the case of cleaning with injection and extraction equipment is much deeper and visible almost immediately.

How do injection and extraction aspirators work?

The operation of these machines, despite being for professional use, is quite intuitive.

They can be used as vacuum cleaners for solids or liquids, they normally have a polyester filter, a clean water tank in which the detergent or chemical product that is necessary for cleaning and another dirty water tank are also deposited.

When the clean water tank is filled and mixed with the right product, we have a small suction hose connected to a pump that will absorb the mixture, to be injected through the hose on the surface of the upholstery or carpet, At the same time, dirt and injected liquid are absorbed and dragged away, this also does a drying job, although the reality is that it will always be necessary to dry after washing or let it dry naturally.

Industrial parts cleaning

How to optimize the bath service life

Quality-oriented industrial parts cleaning is the prerequisite for the success of downstream processes and ensures the proper use of finished products. The specific requirements for cleanliness determine which technical requirements must be created for cleaning. Economic considerations when making an investment should also include ongoing operating costs. Modern equipment for process monitoring and bath care can, for example, extend the service life of baths.

Parts cleaning process with aqueous cleaners

Industrial parts cleaning is often done with water in which washing-active substances are dissolved. These bind the impurities from previous processing steps. The water absorbs the dirt load. When the ability to absorb contaminants is exhausted and the cleaning effect is no longer sufficient, the bath is changed. The period between two bath changes is often determined on the basis of experience. If the period of time selected is too long, there will be a loss of quality in the subsequent process steps. To rule this out with certainty, the bath liquid is often changed too early.

The right time can be determined by clearly defining and monitoring parameters that describe the condition of the pool. This point in time can be greatly delayed by using modern processing technology. The aim is to eject the dirt load and used cleaning agents from the bathroom. A number of material separation processes are available for this purpose. The type of contamination and the cleaning agents used are decisive for the selection of suitable processes.

Industrial cleaning of metals

In most cases, metals are machined using cooling lubricants. An oily film remains on the surfaces on which fine chips and dust accumulate. Other contaminants from which metal must be cleaned can be deep-drawing oils, rolling oils and polishing pastes.

Contamination also includes oxidation products such as rust on ferrous metals or verdigris on copper alloys. The agents for industrial parts cleaning must be tailored to the materials of the components.

Processing techniques

The dirt that is removed from the surfaces during parts cleaning can be roughly divided into solid, non-water-miscible liquid and water-miscible substances. The processing methods used to extend the bath service life are based on the state of aggregation and the miscibility with the cleaning solution. Often used:

  • gravity separation,
  • coalescence separation,
  • centrifugal separation and
  • filtration.

If special requirements are placed on the cleanliness of the cleaning solution, more complex processes can also be considered, such as

  • microfiltration,
  • ultrafiltration,
  • reverse osmosis or
  • distillation.

The equipment used can be installed directly in the circuit that circulates the cleaning liquid (full-flow processing) or operated in a bypass independently of this circuit (side-stream processing). In order to optimize the processes that serve to extend the bath service life, both variants are often used side by side. The aggregates in the off-line processing can be switched on or off as required.

Gravity and coalescing separation

Free oils and coarse solids that get into the bath when cleaning workpieces can be physically separated due to their different densities. The advantage here is that the process does not affect the composition of the cleaning solution. The separators consist of a container in which the liquid can rest. Light oils float to the surface and can be sucked off or drained from there. In coalescence separators, this process is supported by built-in components on which the oil collects.

Heavy components from the parts cleaning sink to the bottom as sludge. From there they can be removed with screw conveyors. In three-phase separators, both processes take place in parallel.

Extend bath service life through centrifugal separation

Solids or oils can be removed from the cleaning liquid faster in centrifugal separators, also known as separators, than in gravity separators. The principle is also based on the different densities of the phases. The heavy components are flung against the outer wall by fast rotating movements, while the lighter phase collects in the middle. Both phases are collected and drained separately. The shorter processing time is offset by higher acquisition costs.

Filtration for a longer service life

Industrial parts cleaning often produces dirt in the form of suspended matter, which can be retained in filters. In order to avoid clogging of the pores in the filter material, coarse-pored filters are used first, followed by devices with increasingly smaller pores. Due to the good cleaning performance of the filters, significantly longer bath service lives can be achieved. The disadvantage is that the filter material has to be disposed of together with the dirt.

Microfiltration, ultrafiltration and reverse osmosis

Microfiltration, ultrafiltration and reverse osmosis are among the membrane technologies. The nature of the membranes means that the smallest particles, organic molecules or salts can be removed from the cleaning liquid. In the preparation of baths for industrial cleaning, these techniques only play a role if ultra-fine cleaning with very small particle sizes in the residual dirt is required.

Distillation for water recovery

Distillation is mainly used in the treatment of bath liquids for industrial parts cleaning to recover the water. The process is based on the different boiling points of the components. With this technique, substances dissolved in the water can be separated. It helps to extend the bath service life because the concentration of these substances can be limited to a permissible level.

Monitoring of the bath condition

When monitoring the condition of the bath for industrial parts cleaning, the concentration of the cleaning agent and the amount of dirt in the bath are determined regularly. If the value falls below or exceeds the previously specified limit value, measures are required to restore the permissible operating conditions.

This includes the automatic or manual dosing of the cleaning agent or the commissioning of cleaning stages for the bath liquid that are temporarily used in the bypass. In addition to the bath control, checking the residual contamination on the cleaned parts provides information about the condition of the bath and the effectiveness of the process.